Functional Biodiversity for Urban Planning: Access to Mitigative Effects and Therapeutic Benefits of UGS

Abstract

The measure of access to urban green space (UGS) informs planning and expectations for implementation, leading to suggested strategies for optimising UGS integration to urban planning to counteract sprawl developments. The article studies the meaning of access to UGS and the importance of UGS type, selection and configuration for urban planning. A literature review guided by the refined wilding (RW) concept analyses common uses and understandings of access to UGS, and the UGS types often studied and recommended. The studies reviewed are from several different countries. This conceptual guidance is explained for its role in improving sustainable urbanisation and lowering risks most responsible for the challenges faced. The meaning of access to UGS as mitigative effects and therapeutic benefits provides scope for optimised measures, monitoring, planning and design of different UGS across different urban plans and developments. Functional connectivity across UGS and transparent spaces with increases in or reserved UGS, no matter the urban development, densification, redesign of sprawl, suburbanisation or other vertical or horizontal expansions in the urban built environment is recommended. Conclusions provide discussions relevant to recommendations and strategies for planning that can decrease fragmentation and loss of natural landscape, including how peri-urban functionally connects to UGS, and an understanding of the benefits of distanced UGS access. The lessons and recommendations from existing studies of well-intentioned plans for UGS in densification planning inform recommendations and strategies for improved implementation. RW provides conceptual guidance for analysis and for urban green planning. The objective of functional urban biodiversity could provide a basis for a standard for UGS in urban planning to ensure long-term positive outcomes.

1. Introduction

Including urban green space (UGS) in urban planning can be for various reasons, increasing access, maintaining the area of UGS, improving functions, and decreasing harmful effects of green, grey and transparent spaces, and the built environment and human activity in urban landscapes. In most cases, UGS are introduced to mitigate the impacts of climate variations, particularly urban heat and air pollution, which are considered worsened by urbanisation, the built environment, industrialisation, energy and vehicle use. Access to UGS by distance from populated areas and distribution is measured for various reasons. Indicators draw attention to use compared to views, distanced benefits, which could be defined as an indirect or direct access, for example.

Recommendations for minimum square metres of UGS per urban landscape and by distance from a home introduced in 2010 and better published in 2017 [1,2] raise questions about how access is understood. Findings of access to various UGS types measured as vegetation cover and density prove utility changes measured indicators [3], with parks more equitably distributed in some studies as compared to other vegetation types, as grasses, forests, mixed and woody vegetation. The various types of UGS are indicative of where and how they can be integrated into an urban plan and development. The same study proves socioeconomic status is influential to access, with higher socioeconomic status increasing access, whereas in other studies, socioeconomic status does not influence access, with urban settlement and development more influential to access, densification compared to suburbanisation, and different suburbs. The definitions or measures of access to UGS therefore require further explanation to ensure urban planning not only includes UGS and for the right reason but also implements these plans for long-term multi-benefits of access, to space and landscape level functional urban biodiversity. Several studies recommend a consistent integration of UGS for urban planning, an integration that is specific to the local landscape. As part of this integration, the definition and measures of access can be further specified, and UGS types can be defined for appropriate selections and configurations in landscape-level spatial planning.

This article will consider how the measure of access varies and informs planning and expectations for planning and implementation, and how UGS is often defined, leading to suggested strategies for optimising UGS integration to counteract sprawl developments. Sprawl developments are avoided with densification and redesign of grey spaces and sprawl itself. Published articles from search term results are selected and reviewed to provide examples of measures for access to UGS and how UGS are commonly defined. The recommendations for improved and consistent UGS integration to urban development are furthered with a conceptual analysis of UGS, which focuses on quality and function at urban space and landscape levels. The refined wilding (RW) concept is explained and suggested for an optimised and advanced function of any UGS designed, redesigned and implemented as part of urban development that prevents sprawl, including redesigning sprawl settlements. The concept provides principles and interdisciplinary guidance and goals for positive outcomes from and for UGS, which are different to but inclusive of optimising spatial configurations for functional landscape-level urban biodiversity. The concept finds its basis in the ecological sensitivity within human realities (ESHR) concept [4].

The beginning of the article provides an overview of RF and UGS for densification. It overviews RW compared to other concepts, and how it is relevant to coverage and distance measures of UGS access, and how UGS is significant for sustainable urban development and implementation of SDGs [2,5]. The article establishes avoiding land use change from the natural-environment and preventing and decreasing sprawl, and the proven negative effects. It also looks to suggest improvement in how the more sustainable urban developments of densification and redesign integrate UGS, and therefore, further implementation. It asks the question, can an improved definition of access to UGS optimise sustainable urban planning? There are various structured hypotheses as a result. Several strategies for urban planning are suggested as a result of the synthesis of findings, informed by studies and recommendations. The strategies are specific to UGS while recognising the importance of sustainable building design and urban planning, alongside the spatial planning for functional connectivity across all UOS, for mitigative effects and therapeutic benefits from UGS access. Some are for policy, and all are for planning and implementation and are responsive to the summarised findings. They will work toward sustainable urban planning, implementation and management that functionally integrate UGS for the development response to increases in population and avoid or improve the negative effects of sprawl.

1.1. Urban Planning for No Land Take Strategies

The ‘no net land take by 2050’ is a target of reaching land take neutrality by 2050 [5]. Human settlements, new cities, densities, expansion and planning will all work toward conserving the natural-environment from urbanisation. Redesign of urban space use, indoor or open spaces, is most important for sprawl at a landscape level and is significant as a strategy for any urban development, as it addresses no net land take strategies and goals. The recommendations are then to integrate UGS for sustainable urban development. How they integrate UGS is specific to each development type. Densification over horizontal expansions is recommended to accommodate population growth. For horizontal expansions, improvement in suburbanisation, and redesign of sprawl is recommended.

1.2. Rapid Urbanisation Changes UGS Configuration

UGS configuration by spatial planning, and UGS type, and quantity and quality, is often negatively affected by rapid urbanisation, like sprawl, and also by densification. Either due to limited plan integration or limited implementation of plans for UGS. Rapid urbanisation can result in unplanned developments and sprawl, or rapid urban planning, without the required time or stakeholders to ensure integration of UGS for sustainable urban development influenced by urban policy, planning and implementation. Sprawl as a result of rapid and unplanned urbanisation often results in a conversion of the natural-environment to low-quality changes in use, normally for the built environment. Densification, while preferred as a sustainable urban development over sprawl or other horizontal development, referred to as infill development, is attributed as the primary cause of UGS removal [6].

Losses of green space for densification in 2020 are still a policy and scholarly concern [7]. There are three types of sprawls that afflict growth throughout the planet: the low-density sprawl of higher-income regions that have become auto-dominated; the low-income sprawl that isolates the poor from economic, social, and cultural opportunities; and the high-density sprawl of super blocks, towers, and isolated uses that have emerged in China and other Asian countries. While each is very different, they share common urban pathologies: isolated poverty; water, air and land pollution; congestion; loss of community; degraded health; and economic headwinds, to name a few [8]. There is a need to monitor urban development patterns more closely [9]. As densification is an improvement to sprawl and a now common urban development type, referred to as high-density cities, compact cities and 15-min cities, their integration of UGS is significant for sustainable urban development. Strategies to integrate ‘green-grey’ infrastructure [10] such as green roofs, front gardens, green balconies, pocket parks or vegetation on wires [11] commonly lack the scale of impact to counter the trade-off between urban greenspace and densification [12]. Developing compact cities without losing UGS is a recognised challenge. Haaland and van den Bosch [13] provide a valuable overview of growing evidence of the loss of UGS due to densification processes. The results show that densification indeed decreases the quantity (Amsterdam: −4.7% Brussels: −11.9%), average size (A: −3.1% B: −25.6%) and connectivity of UGSs.

1.3. UGS Supply and Human Demand: Realities for UGS Access for Densification and Suburbanisation

The question of human demand is informed by socioeconomic status, but also by the location of the population [14]. City centre residents are often in demand of and value UGS, no matter their socio-economic status, and have a low supply, with high access to services. Suburb residents have a lower supply of services and less access by convenience, often requiring a car [15]. In city centres, there is therefore low green supply and high human demand [16]. UGS can, however, push lower socio-economic populations out to suburbs, which deters from implementation, as value increases. These factors make the balance between UGS increases and equitable access in city centres a significant consideration for densification, while intending to improve equitable access to urban centre UGS. The redesign of sprawl and suburbanisation is different, with suburbanization’s access to residential UGS and public UGS, leading to recommendations for quality and landscape connectivity improvements. Then, built environment and infrastructure improvements for transport and sustainable access to services. Redesign for suburbanised areas might also be part of urban planning.

1.4. Theories of Urban Planning

Theories of urban planning indicate the importance of working with various stakeholders and sectors, and throughout the life cycles of each plan and implementation strategy. As a theory of planning to rework and ensure implementation of good plans for UGS integration, particularly for densification and also for horizontal expansions by land allocations and selections for expansions, these ideas support zero land take strategies. The new SDG 11.3.1 [5] ratio of land consumption rate to population growth rate for sustainable human settlement planning requires redesign of the existing built environment and urban land uses, including UGS as a priority in urban development plans, particularly for densification. Theories of urban planning to address sprawl, and UGS integration are included as considerations. UGS integration refers to the reserved natural-environment and urban greenery, as introduced and established UGS of different types.

The literature acknowledges the significant variations in urban planning theory, noting the increasing complexity of factors contributing to urban sprawl. Among the factors contributing to urban sprawl, the implementation of land use policies and urban planning is particularly significant, especially concerning the access to land, housing ownership, building processes, and policies influencing urban and residential development, resulting in substantial variations in urban sprawl across countries [17,18]. A planned horizontal urban expansion provides an opportunity for prioritising redesign and conserving the natural-environment. Densification provides an opportunity for vertical expansions to prevent horizontal increases in the natural-environment and to build environmental conversions.

The life of an urban plan and the opportunity for implementation of revised plans can improve how urban plans that are not implemented still achieve intended urban development goals, particularly sustainability goals. This is particularly important for aspects of an urban plan that are significant for sustainability. Permeable surfaces, layout, and urban greenery quality and optimised coverage are examples of significant urban plan aspects for sustainability.

Synchronised urban planning by profession, and even specific professions, to improve how UGS is integrated can result in different UGS types, spatial configurations, reserved spaces, decreases or increases. A point relevant to any urban development type.

The first point for urban planning theory is a matter of prevention, the second point is a matter of time for implementation and revising plans, as plans informed by implemented urban developments, for improvements in unimplemented aspects of a plan and outcomes. The third point for urban planning theory is a matter of how a specific profession in the urban planning process is motivated to integrate UGS, and the quality and type of UGS they will integrate.

1.4.1. Pre-Emptive Urban Planning and Strategies

The various typical types of urban development, such as sprawl, unplanned urban development, suburbanisation, planned residential horizontal development, and urban centre increases, by built environment for services, polycentres, or densification, vertical residential build up for population increases, require specific urban development strategies. These urban developments are to accommodate population increases and population movements caused by various factors, including urban migration and gentrification. Sprawl as a particular challenge in urban development is unplanned and often unsustainable due to the use of the natural-environment for horizontal expansions, by the quality of the built environment implemented, and vehicle requirements to access services, leading to increases in air pollution. Sprawl in sustainable urban development must often be redesigned for sustainable use, with vehicle and service access as part of the redesign. Suburbanisation and densification are alternative development options to sprawl; they are planned and preventative. Suburbanisation is a planned horizontal expansion of the residential built environment, often including residential gardens and public parks. The need for vehicles to access services is still a challenge due to air pollution. Densification is a vertical expansion and a different urban development strategy, of redesign and building up from the existing urban centre. In most cases, sprawl developments are unplanned and can be prevented with vertical expansions in the built environment to accommodate increases in urban population, also referred to as densification. Or counteracted with redesign of sprawl settlements, and or with planned horizontal expansions that include redesign and reuse of existing human settlements, that ensure conservation of the natural-environment, built developments that minimise negative impacts on the environment, and that might provide services closer to where the horizontal expansions are located. These closer services might be a result of polycentric developments or efficient public transport, which decreases reliance on vehicles. The redesign of abandoned spaces, urban growth boundaries, and polycentres around efficient public transport hubs that provide services and residence closer to services, to decrease reliance on vehicles, are combined strategies that must integrate UGS effectively to address sustainability concerns.

1.4.2. Ongoing Urban Planning and Development

An urban development can refer to the process of planning and implementation for urban development as an in-progress development, or can refer to a completed urban development, as a new urban settlement or design for a long-existing urban settlement. The objectives or goals for any urban development that intends to reach sustainability, by SDGs or other guiding principles of sustainability, can be planned and eventually implemented over the ongoing process, with UGS plans adapted after the implementation of built developments through evaluation, evidencing changes required for long-term outcomes from implemented plans. Additions over time can lead to improved plans, designs and outcomes, as plans for UGS respond to the use of the new built environment. The example of unimplemented UGS despite reserving or increasing UGS in urban development is suggested as a longer-term process of additions like UGS over the years after the first development is completed. It can therefore be seen as an ongoing, rather than a completed, partially unimplemented planning process.

1.4.3. Urban Planning and Synchronised Improvements for Urban Greenery Design

A focus on improvements in UGS quality and advanced function and functional connectivity leads to a different aspect of urban planning, which is relevant to densification, and sprawl and city centre redesign. Urban planning as adaptive capacities of planning and design, with the UGS aspect for implementation open to adaptive planning after implementation and use of other aspects of urban development [19]. Research advocates for a hybrid approach, where improvements in policy, organisational strategy, and designers’ abilities are made synchronously. Simulation results show that a 10% improvement in these areas could boost green design practices by as much as 40%, reinforcing the importance of systems thinking in addressing the dynamic nature of green design motivations [20] Li et al. [20] focus on the influence of designers in urban development and integration of UGS and green planning, which is relevant when designers are part of an urban planning and development process and have independence and autonomy in their designs. They find that a designer’s green motivations are influenced by intrinsic motivations and external regulations, despite inclusion in planning and even decreases in UGS with densifications [6,7].

Urban planning processes can therefore determine how a designer’s motivation for greenery determines plans and implementation. This point is different to planning compared to implementation, where planning with a hybrid approach, or multi-line improvement approach could improve implementation. As implementation is never ensured, it improves the likelihood of urban plans being comprehensive in addressing challenges faced by urban landscapes and settlements with sustainable features proven to prevent or mitigate. Where urban plans are not implemented, they can be further evaluated as an opportunity for new planning to adapt to existing urban developments, improving how urban developments address long-term challenges. Improved designer motivations for urban green development can improve an evaluation of new urban development and or existing plans, implementation and outcomes, including the feasibility of more advanced function intentions, and optimised spatial configurations, and UGS selections.

1.5. Urban Planning and UGS Access: Equity and Sustainability

An improved urban planning for population increases, including integration of UGS, would decrease the need for redesign of any urban development. There are two levels of urban planning and strategies to address how rapid urban planning could integrate UGS and become pre-emptive planning, which prevent further sprawl and the various reasons for it [8,9]. They can also improve how densification, redesign of grey spaces, suburbanised areas, and sprawl maintain or increase UGS coverage, improve UGS quality, and optimise access to benefits. Policy could be better developed and implemented, to further how urban planning integrates UGS. Urban planning can provide an opportunity for in-depth UGS integration that can optimise spatial distributions and UGS type selections, and functional connectivity according to the aims of equitable access. This planning and integration of UGS is recommended for all urban developments, sprawl redesign, densification, and suburbanisation. The informing concepts and aims for urban planning are relevant and important for achieving sustainable and equitable urban development goals. Higher socioeconomic areas are also low in UGS access with supply-demand mismatches [15,20], despite common findings of inequitable access to UGS by common measures, of coverage and distance. Observed land-use changes seem disconnected from purported urban greenspace policies, whereas urban development plans seem to dominate changes in greenspace quantity and form. These processes have been found to affect the quantity, connectivity, accessibility, size and quality of green spaces.

Urban planning for densification can better arrange existing UGS to avoid encroaching on the edges of UGS by construction land rather than being sliced directly into smaller patches [21] and can avoid the loss of UGS [6,7] as different to maintained UGS by area, and or increases. It seems very difficult to achieve a more compact city without losing UGS. Including UGS can address functions sought by renaturing, which is a mitigative effect [22]. Mitigative effects do, however, vary and require different measures of access. Air pollution decreases for intra-urban suburbs, and mitigative strategies are needed, which could be addressed by UGS, where urban cooling might not require mitigation [23,24,25,26,27,28]. UGS can also achieve human health outcomes [29,30] by preventative design and access. The guiding concept for UGS urban planning integration is influential in the provision of functions provided by access.

1.6. Refined Wilding and Urban Planning

Conceptual guidance for urban planning could ensure UGS integration and that no net land take strategies are achieved. RW [31] for functional urban biodiversity encourages focused interdisciplinary knowledge to inform urban planning for advanced function in UGS. It is a concept for urban planning and for any stakeholder involved in UGS integration. Synchronised planning, designer motivators [19], optimised spatial configurations, functional plants, trees, shrubs and grasses (PTSG) selections and assemblages, and UGS type selections are all guided by RW as a concept and principles. The human realities aspect of the ESHR [4] introduces urban planning realities of ensuring implementation, even over time, and informed planning.

1.6.1. Spatial and Temporal Scope

The RW concept, as substantiated by the ESHR, refers to all urban landscapes and their functional connectivity, while normally focusing on urban landscapes of cities of individual or multiple centres, and their surroundings. Functional urban biodiversity is therefore conducive to measures of spatial equity. The temporal scope of RW encourages a historic land use evaluation, and appropriately responsive planning for the objective of functional urban biodiversity according to the principles of the ESHR and specifically RW.

1.6.2. Refined Wilding and High Quality UGS for Densification

While densification is a sprawl avoidance strategy, it does require UGS integration. Densification for urban development is a vertical expansion of the built environment to accommodate an increase in urban population. UGS is valued but limited in supply in high-density areas and does require integration for densification. In most cases, UGS is not often integrated or reserved and sometimes lost during densification. RW encourages functional urban biodiversity [31] as an urban biodiversity and UGS concept. It is developed from the ESHR [4], which aims to achieve functional biodiversity by addressing sensitivity to ecological interactions and processes, and human realities of the given landscape. Functional urban biodiversity, therefore, looks to achieve functional biodiversity as substantiated by the ESHR for an urban landscape. RW is the specific or substantiating concept for the theory of functional urban biodiversity. It works to implement wild refined UGS appropriate for each urban development and landscape, with selections of wild plants, trees, shrubs and grasses (PTSG) and functional assemblages. The ESHR emphasises balance between functional ecological interactions and processes, and human realities and a sensitivity to the two aspects of the concept for functional biodiversity outcomes. Wild PTSG selections are valued for being conducive to semi-natural UGS and for conservation of genetic resources. A necessary part of RW for urban planning and implementation is defining and identifying appropriate UGS types by required and desired functions, which determine assemblages and selections of PTSGs. RW also works toward an optimised advanced function of urban biodiversity, at UGS and then at the functional landscape scale. The various measures to determine UGS coverage and quality, by functions, to monitor before and after urban planning and implementation, are relevant to proving and discussing how standards for UGS integration for urban planning, particularly densification, could be developed and used. Spatial distributions and UGS type selections are examples of how refined wilding can conceptually guide urban planning for UGS integration and access.

1.6.3. Maintaining or Increasing Quality and Coverage of UGS: Spatial Distributions

UGS are recognised as a necessary aspect for sustainable urban development. Access to UGS by coverage and distance is often a relied-upon minimum standard for inclusion in urban landscapes. How to include them, by access, quantity and coverage and quality, and their various types, is still being studied. These studies are interdisciplinary and measure functional outcomes and are specific to urban development sites. The example of urban cooling and the importance of spatial configuration emphasises the landscape-level planning of UGS alongside the planning of individual green spaces. In the example of the cooling effect, there is some controversy in the research on the cooling effect of trees and UGS configuration [23]. One study has posited that the spatial distribution of UGS holds greater significance than the shape of individual patches [32]. Peng et al. found that the morphology of blue-green spaces is more influential than spatial distribution in the cooling effect [23,33]. It is important to study the influences of UGS configuration on LST variations. However, blue spaces and vector-borne [34] and zoonotic disease [35], as well as contaminated or polluted water and impacts on human health, must be considered.

1.6.4. The Variability in Example of Optimised UGS Coverage by Urban Development Type

According to the theory of the City Life Cycle, suburbanisation was regarded as a sequential stage of metropolitan development. It requires the effective use of small and medium-sized UGS to reduce LST, such as the polygonal UGS with mixed vegetation and close to water bodies [18] while controlling the expansion of construction land [7]. Examples of intact farmland converted to construction land [6] are where expansions lead to negative impacts on the natural-environment from urban development. These expansions can be decreased in negative impact with green belt planning and ensuring urban greenery as part of any implemented urban development plan. The densities and cooling. The amount of tree planting needed to lower pedestrians’ level air temperature by around 1 °C is approximately 33% of the urban area. Consistent integration of UGS can optimise spatial patterns and provide a controlled expansion of the UGS area to alleviate thermal stress. Lin et al. [36] find land surface temperature (LST) reductions respond to UGS by patch cohesion, density and landscape shape, differently from cooling effects, where optimised spatial patterns improve cooling but not LST in Ghangzhou [37]. At the same time, expansion and connectivity between patches are proven to mitigate high heat exposure [38]. Venter [19] significantly finds that while cooling is an important factor or function to plan for, air pollution is a more significant factor for equitable UGS access and for urban planning. Air pollution can be variably mitigated as a matter of proximity to access.

1.6.5. Maintaining or Increasing Quality and Coverage of UGS: PTSG Selections, Assemblages and UGS Type

The normalised difference vegetation index (NDVI), Light Detection and Ranging (LiDAR) and biotope are measures of UGS coverage that consider vegetative densities, tree canopy cover and are closer to measures of ecological structure for various values. Some aspects of each indicator and measure identify PTSG selections and assemblages, and designate UGS type. More specific identification of UGS type [39] for urban forests, and more specific selections of UGS type for function determined by PTSG selections [31] can improve understanding of functions and therefore the benefits accessed. It can also improve how access to UGS leads to positive impacts and outcomes. While UGS coverage is normally a beneficial access, the PTSG selections can lead to negative impacts, and elevated compared to pedestrian level UGS can provide variable benefits of access. In both cases, allergenic compared to non-allergenic PTSG selections and assemblages, and optimised UGS selections for functional landscape connectivity lead to negative effects on the air of transparent space, for reasons of pollen emissions [40]. Effects are worsened by air pollution combined with allergenic pollen emissions [40,41]. The functional ecological interactions and processes and their suitability for human realities, not only by planning and implementation, and design influenced by perspectives, preferences and interests, but also by functions needed, and access to resources. UGS type selection can also determine how suitable UGS are for urban landscape human realities, and expectations for ecological complexity and use, determining access to benefits.

1.7. Refined Wilding Compared to Other Urban Greenery Terms

RW can advance existing knowledge and guidance provided by already used urban greenery terms. The terms include renaturing, novel urban ecosystems, novel landscape design, wildlife-friendly, and meadowscaping, see Table 5 in [31]. The cited example of existing terms [31] is used by various landscape architects, gardeners, urban designers and planners, and ecologists. They emphasise how the inclusion of diverse wild crops and plants using design systems can improve functional biodiversity outcomes and address human opinions of what is acceptable, safe, aesthetically pleasing, and manageable. In urban landscapes, addressing human opinion is as important and required as the ecological principles for functionally biodiverse UGS. This last point is supported by the ESHR. At the same time, RW aims to maintain and introduce or establish urban green systems that function as semi-natural or natural systems with low maintenance required, which is a mimic design of a natural system. Biophilic design [42] encourages the connection between nature and the built environment, including building materials and building design that mimics nature and includes greenery. The inclusion of greenery is relevant to RW, and the sought continuity between the built environment and natural-environment introduces complementarity between the concepts. Green infrastructure encourages an understanding of greenery and sustainability integrated into a landscape’s built environment, public and private, and particularly a connecting function for the landscape, where the built environment is a connected landscape. Infrastructure is referred to as providing the basic and essential physical and organisational structures for societal, economic and environmental functions. It includes public utilities, transport systems, public services, telecommunications, digital and personnel that operate and work for and in the infrastructure. Green Infrastructure addresses a balance in this function, ensuring the physical and societal function of these structures is sustainable. The integration of greenery to infrastructure is relevant but different, and RW is a concept that can complement and be included. Green infrastructure [43,44] comparatively encourages the landscape-level consideration of connectivity and function that RW does. Green infrastructure could easily use RW for greenery integrated into an urban green infrastructure, resulting in an advanced function of greenery through an urban infrastructure that presents fewer impediments to the sought outcome. This integration is part of an understanding of human realities, as human resources that work for services and plan, implement and evaluate the green infrastructure of an urban landscape. RW could increase mainstreaming of green infrastructure for urban greenery, understanding of the function and benefit of UGS [31,38,45,46,47].

Biophilic design and green infrastructure differ by being building-specific, with residential or public greenery adjoined to the building relevant to RW. Green infrastructure refers to an entire urban landscape, including public services, human and nonhuman, and the built environment, past and present, including buildings. In most cases, green infrastructure is a landscape-level approach and uses ideas of landscape and functional connectivity, but requires specific consideration of green space [45]. Biophilic design might integrate ideas for landscape continuity or connectivity, but is generally specific to a building. This gives both terms similarity with RW and functional urban biodiversity, which is specific to the natural-environment and integration of high-quality semi-natural-environment systems which functionally connect across an urban landscape, and across different urban landscapes. It also specifies the use of wild PTSGs, which adds to how either term or concept includes urban greenery and nature to its design, and infrastructural service plan, implementation and operation. It also ensures a consideration of human realities in design, and infrastructure could and does. This is an additional aspect of RW that could improve design, and how infrastructure is green, and is how it could easily be used by both concepts, as both include and already consider human resources for design, planning and implementing and for services. In addition to specific considerations of access to wild PTSGs, knowledge sets for design and implementation and maintenance, and preferences that encourage or are barriers to refined wild UGS. RW also takes these concepts a bit further by encouraging wild PTSGs alongside advanced function intentions. While wild native and nonnative PTSG selections are a focus of the concept, advanced functions by non-allergenic, and landscape-level functional connectivity with semi-natural green spaces that self-maintain and provide mitigative effects, and therapeutic benefits are also important. Wild PTSGs and their loss is a significant conservation topic. Conserving these wild PTSG as genetic resources in-situ [46], as RW does, is a conservation strategy, as lab and seed bank stores of wild PTSG genetic resources are. In some cases, wild varieties are not as robust to climatic variations, and the UGS must be robust as a system, providing microhabitat and protective functions from climatic variations and other mitigative effects sought for human populations in the UGS itself.

1.8. Hypothesis

The measures of access to UGS as minimally required by the WHO, 9 m² [1,2,47] could be further categorised and defined. A thought process for advancing the hypothesis is the following:

Access to the benefits of UGS can provide an improved reasoning for UGS introductions, selections, and locations.

Improved reasoning can improve planning motivations, stakeholder diversity, resourced interdisciplinary knowledge sets and synchronised developments.

Improved motivation for interdisciplinary knowledge sets and urban greenery benefits from access is conducive and aligned with RW.

RW can guide urban planning integration of UGS, with a focus on the advanced function of each UGS and of connectivity across UGS and transparent spaces of an urban landscape. This advanced function is, as part of the concept, reliant on UGS selections, locations and spatial configurations, and more specifically, PTSG selections and assemblages.

The eventual findings intend to better inform urban planning, in terms of UGS coverage, the importance of distance from compared to distant benefits, and the selection of UGS types.

2. Method

To optimise UGS integrated urban planning, particularly for densification and avoiding the negative outcomes of sprawl, definitions of access to UGS and UGS types are analysed. A literature review looks to discuss influential factors for response to recommendations for improved access to UGS, particularly in the case of urban planning. It considers the benefits or functions of UGS for human populations and for the natural-environment. Findings are to inform how access and the benefits of access are influential in planning. These benefits and planning for improved access can also be influenced by the various definitions and types of UGS as an influential factor for the effect of exposure. UGS type can determine functions and expectations for UGS included in urban planning and implementation. The selection of articles for review and information extracted and identified as an informant for analysis is an example of sought information from various search result pages and informed by existing knowledge and cited studies. The selection and analysis are informed by urban planning and by the refined wilding concept. The reason for integrating and including UGS in urban planning must be clear for increased inclusion in planning and implementation. This clarified reasoning can improve goals and objectives for UGS and design, eventually advancing the function of any urban biodiversity.

2.1. Significant Terms for Review and Findings

Access to UGSs is a focused idea for sustainable urban development. Equitable access considers a socioeconomic and demographic difference in access, which is balanced to provide even access to the relevant population. This article and review look to emphasise the meaning of access according to the various benefits of UGS, which furthers the idea of and planning for access. In most cases, distance and coverage are defining indicators of access, and the overview of selected articles provides discussion about how access is understood, and therefore, urban planning is influenced by recommendations of access. Coverage is often a matter of urban greenery, with measures of NDVI, as vegetation and density. There is often a measure of provision by proximity and distance, with some specific recommendations for highly populated, densely populated urban areas. The examples of various benefits of UGS lead to an in-depth understanding of access from selected existing studies reviewed from search term results. It can better inform urban planning and evaluation of UGS integration, as coverage that leads to a specific benefit. The measure of benefit then leads to an understanding of distanced mitigative or therapeutic effects, which add accuracy to evaluations of urban plans and implementation outcomes from urban plans. Particularly for urban plans that result from increases in urban populations. Access is sometimes measured as exposure, which adds meaning to how access is a measure of effect from a UGS. Exposure can also lead to an understanding of awareness of access and then benefit. The categories of access introduce the fact of access and benefit. Exposure without awareness, particularly for distant green spaces of high quality and advanced function, might not be understood with the same meaning of definition. Provisioning is often referred to as a physical proximity of a UGS; however, provisioning is also introduced as a consideration of access to benefits. A UGS of greater distance can provision benefit and, therefore, access to a UGS.

Refined wilding (RW) is a concept for functional urban biodiversity which encourages functional landscape-level connectivity across and between different UGSs and transparent spaces. Transparent spaces are air and aquatic spaces, and for RW are specific to an urban landscape. Landscape connectivity encourages an urban planning approach which recognises landscape and smaller-scale aspects of connectivity using the ESHR concept and aspects of functional biodiversity. Functional connectivity of urban biodiversity as ecological interactions and processes, and human realities of interest, access to resources, planning and implementation capabilities, and balance between design and long-term outcomes related to ease of maintenance. And to transparent spaces in functional biodiversity terms, which is relevant to human realities of health, and mitigation effects, and therapeutic benefits and the influential connectivity between UGS and transparent spaces, and transparent spaces and human health. Optimising urban planning for UGS integration is suggested by determining the benefit of access required and then ensuring an advanced function of any UGS and selection of UGS across a landscape. RW is a suggested concept for such optimising in terms of sustainable urban planning. As this optimising of urban planning is recommended for densification, densely populated urban developments, and for redesign of, or to avoid sprawl, spatial planning horizontally and vertically for urban landscapes is relevant. Terms like elevated and vertical UGSs are often used for walls and rooftop greenery of various types, as compared to the pedestrian level. Then periurban greenery, which is UGSs in the surroundings of urban centres and landscapes. They are normally of larger sizes. Sprawl is an unplanned horizontal urban development of the built environment, which often results in degradation of the natural-environment and low-quality urban settlement with reliance on vehicles for access to services. Suburbanisation is a planned horizontal urban development and settlement which often includes urban greenery as residential and public spaces. These urban settlements often still require vehicles for access to services. Vertical urban built developments and settlements often result in a loss of UGS and are least frequent by coverage; they are a densification or a densely populated urban area which relies on high rises. The urban planning for the three urban settlement and development types is for the same reason of increases in population, but each requires a different UGS integration by spatial configurations of selected UGS type for functional urban biodiversity and RW.

Densification requires elevated and vertical UGS, even smaller UGS sizes, which can provide an urban biodiversity that functionally connects with surrounding urban greenery. While sprawl redesign might lead to increases in pedestrian level UGS of residential gardens and public urban greenery, and green belts to increase greenery and functional biodiversity lost from sprawl developments, even improved quality of urban greenery in surrounding urban settlements, as redesign or UGS integration to suburbs might. All UGS integration to urban planning can therefore lead to maintained or increased UGS, which optimises access by spatial planning and configurations of selected UGS types for benefits by mitigative effects and therapeutic benefits, as a functional urban biodiversity outcome. This function is an urban space, and a landscape connectivity level outcome, with functional connectivity across UGS types, and across transparent spaces, ensuring optimised benefits in terms of access. This ensures access is understood as physical access as well as the less obvious benefits that close or distant access to UGS of various types can provide. The idea of UGS provisioning can then be further specified and planned for according to access to various benefits of different UGS types. The benefits of access to UGS are then categorised into mitigative effects, with air pollution and urban heat and variable temperatures as examples, and therapeutic benefits. Mitigative effects refer to preventative and responsive measures to reduce harm, whereas therapeutic benefits refer to improvements on a normal basis, such as improvements in health. The RW concept then substantiates the ecological aspects and human realities of UGS.

Access to UGS by vegetative cover and distance can then more easily consider UGS type, and different types of benefit that can be experienced from further distances compared to proximity by physical closeness. These more specific measures can inform and lead to improved urban planning for UGS, by RW and functional urban biodiversity across densely populated built environments, and urban settlements of sprawl for redesign, and suburbanisation. The ESHR provides a conceptual basis for RW and aims to achieve a functional biodiversity outcome. Outcomes are referred to as an evaluated and or measured output resulting from various coordinated inputs. For RW, the sought outcome is functional urban biodiversity at individual green spaces and landscape connectivity between every UGS, and influential flows between every UGS and transparent and grey spaces. Gray spaces are defined as under-utilised and neglected built environment or natural-environment spaces. They can also be referred to as abandoned spaces. Gray spaces refer to informal human populations and the built and natural-environment used by them. These spaces are significant for green space planning, as they can integrate and become green spaces of various uses, or can be utilised for different purpose, particularly for horizontal or vertical redesign to accommodate increases in urban populations, and improved sustainability of and for existing human settlements, while integrating green spaces as proportions of any urban open space as a redesign of gray or gray spaces, where proven as beneficial and accessible according to the RW concept, and the ESHR.

2.2. Literature Review

The articles reviewed consider definitions of access to UGS and reasons why UGS are encouraged as a sustainable development. The definition of UGS is also included in search terms and articles reviewed.

2.2.1. Two Literature Searches

ProQuest is the only search engine used and is explained as a search engine that provides relevant and representative search results.

The first search for literature is to define and categorise access to UGS, with search terms ‘UGS and access’ and ‘urban planning and UGS access’. The results were reviewed by title, and an advanced review of a selection of articles led to an understanding of examples of how access to UGS is defined and studied, for the first search term: 22,311 results. After filtering for the last five years, 5191 results are reviewed for title and abstract.

For the second search term, 3955 results were filtered for the last five years. 1033 results are reviewed for title and abstract. The second search for literature is to list UGS definitions and types considered in publications, with the ‘UGS definitions’ search terms. 10,460 results, and with a last five-year filter, 282 results were screened for appropriateness and definitions of UGS used. Search results from the last 10 years as scholarly journal articles are 795 results, and in the last twelve months, 69 results. After screening of articles using advanced review, reading past the title and abstract, 26 articles are listed as examples and organised into a table.

Both literature searches include advanced selection and review of particular articles, for findings of access to benefits of UGS, common definitions of UGS used, and specific UGS types and definitions, which further specify expected or intended benefits from access.

The selection and exclusion criteria for an advanced review of the first search results include (1) studies about access as benefit with the initial understanding of close distance and coverage; (2) study aims including reason for promoting UGS, which is indicative of understanding of benefit and access, and (3) the most frequent terms used to refer to UGS. For the second search results, advanced review of articles is to (4) identify UGS types. These advanced reviews, by reading the article, not just the title and abstract, provide further information about definitions of UGS and measures for all three searches, and for both literature searches.

2.2.2. Filters for Search Results

The second literature search uses the search engine ProQuest with search terms ‘UGS definitions’ with filters selected: the last five years, scholarly articles and for 48 of the 102 subjects included. The last five-year criterion is selected as it gives recent articles for UGS definitions and access meanings which are representative enough and within the time since the WHO recommendations for minimal coverage by distance from home. Scholarly articles and subject inclusions. Urban planning; green infrastructure; urban areas; cities; open spaces; urbanisation; climate change; remote sensing; vegetation; sustainable development; biodiversity; land use; parks and recreation areas; sustainability, or as part of improving vertical expansions, and or redesigning or any already established urban development.

2.2.3. Limitations

Search Engines

Google Scholar and ProQuest are presented for a different study ]. An example of how search results are different between two search engines indicates that a review of search term results can be sufficient for ProQuest. While inverted commas for search terms can influence search result numbers, as Google Scholar searches respond to, there is a similar random representation in search results and articles to review between the two search engines. Future literature reviews could obtain search results from both search engines.

Filtered Search Results: Last Five Years

The last five years is a search result filter to narrow reviewed articles to recent and after more available publishing of the WHO recommendations for 5 m² minimum in 2017 [1,2], which is referred to as a 2010 minimum in 2018 [47]. This minimum is often increased and city specific. Some selected results are from between 2012 and 2020, which is outside of the five-year filter search for results for ‘UGS definitions’. It is an error in the search results and the search engine. They are selected for relevance found in screening and selecting. They can be considered as the number of years this topic, UGS definitions, has been studied. Screening search results from the last ten years or longer would provide findings that reflect long-term consideration and study of access to UGS, and UGS definitions are often referred to, used and UGS types studied in published articles.

2.3. Analysis

The analytical process includes advanced review of selected search results, and conceptual analysis, an analysis guided by the refined wilding concept for functional urban biodiversity, an urban biodiversity theory. The analytical process leads to an understanding of access to the benefits of UGS, with the distance and coverage of UGS as a basic reason of integrating UGS into urban planning.

2.3.1. Analytical Process

The selection of articles that identify and study different benefits leads to a categorisation of not only benefits from UGS, but also an idea of access to benefits, rather than an idea of physical access to UGS and subsequent benefits. The analysis of the selected articles, therefore, leads to a more specific definition of access to UGS and why it is significant for planning. The initial selection criteria for search term results led to access and benefit categories for inclusion. Further categories are the mitigative effect for air pollution and urban heat, and therapeutic benefit with UGS types and selections, furthering considerations for planning and analysis. This analytical process then leads to a review of UGS definitions and how they are considered in various studies. The analysis of UGS definitions contributes to discussions of the significance of defining and selecting UGS and analysing and planning for function at space or system and landscape connectivity levels, as the ESHR and RW are encouraging of. The analysis can also lead to an emphasised planning of landscape-level connectivity of different UGS, existing and new, and UGS selections that are optimised for appropriateness according to the urban development.

2.3.2. Refined Wilding as Conceptual Guidance for Analysis

In most cases, the search results and articles reviewed were screened for initial measures of access and benefit. The ESHR is used for the initial organisation of findings. Then, RW specifically for urban greenery, and for UGS definitions, the types, as an analytical framing. This concept is also used for the search term selection of UGS definitions, and for the analytical process of UGS types, and urban development type, with advanced function, particularly, functional landscape connectivity across all UGS types, and transparent spaces for human health, and environmental outcomes. The RW concept provides a consistent conceptual frame for all considerations of benefit from access, and for any UGS type. It does give significance to the UGS type for planning and design, and evaluation, and expectations for advanced function, PTSG assemblages, and human use.

2.4. Organisation of Findings

Table 1 presents the initial organising of findings from articles reviewed, which leads to an introduction of access to benefits and how distance is determinant to access to benefits of UGS, as compared to physical access to UGS. Eleven benefits are listed; some are similar, and they lead to identifying the two categories of access, which can further inform urban planning. The eleven listed benefits, with several selected articles cited, easily categorise into mitigative effects and therapeutic benefits. The ESHR column compares measures of benefits to the two aspects of the concept. Table 2 then organises examples of findings of access by the two categories and introduces measures of access for each category. The two main columns are for mitigative effect and therapeutic benefits as measures of UGS access. The significance of distance and physical access as influential to the mitigative effect or therapeutic benefit is rated with dependent, independent or variable for distance, physical access and vegetation, PTSG selections as measures of provisioning. Proximity measures are in the second section of rows, as accessed by physical access and distance. Table 3 further categorises some of the benefits of UGS with advanced considerations. It presents five categories with in-depth benefits of UGS access for transparent spaces, therapeutic benefits and ecological and environmental benefits of UGS. Table 4 and Table 5 provide an overview of common definitions used in advanced review articles, and then different UGS types specified in search results from the search term ‘UGS definition’. Table 4 lists the articles reviewed and the different UGS types considered. Table 5 lists the 38 different UGS types and the urban developments that they are appropriate for. The tables indicate the analytical process for access categories as access to benefits, distance as a variably significant point for access, UGS definitions and specific benefits, which are to inform UGS integrated urban planning.

Table 1. Ideas of access.

Benefit	Distance	Measure and Result	In Addition to Distance	ESHR
Needs of the community and human health. [48] Human utility and biodiversity [49]	Parks and greenspaces, undeveloped public land for future park and green space development. Availability of UGS. Access by design, for features, creeks, playgrounds, paths. Access, utility and inclusiveness. As different aspects. Accessible by area available and by multifunctional design Design for utility and distance. Access is by utility of 639 UGSs.	Being physically active in a UGS. Exposure (which leads to other measures that result in benefits of mental health, social cohesion, lowered risk of psychiatric disorders, and psychological distress, type II diabetes, quality of sleep, healthy weight, and cognitive abilities. Multifunctional UGS with recreation, nature, natural-environment activity (nature play), sport. Public health, community, government, environment: nature and forest therapy, sports and recreation, nature play. Optimising balance between human use or utility and biodiversity. Human utility index.	Transport other than pedestrian to UGS. Bicycle, public or private transport and pathways and roads for access which make further distances more accessible.	Health focused HR ESHR
Mitigative cooling versus air quality and pollution decreases. Building height and pedestrian level cooling effect.	33% of urban area for 1 degree of cooling for ground pedestrians. Rooftop greenery and cooling for localized environment. ground level cooling in 2012 and in this study was not proven. Rooftop greenery in open layout has cooling effects at pedestrian level, but building height negatively correlated with pedestrian level cooling. Green roofs outperform cool roofs. Urban green areas (UGAs) have the ability to moderate temperatures in not just the immediate region but also the surrounding area in a process referred to as the cooling effect [24,27,49,50,51,52,53]	Accurate measures of cooling effects. [50] Cooling and temperature regulation. Indirect health from mitigating UHI. [51] 43 megacities The cooling impact of urban greening: A systematic review of methodologies and data sources [53].	Cooling effects for distanced locations, by elevation or horizontal distances. Influenced by vegetative cover, quality and type, but not as much by closeness to the UGS	ES and complexity and function can determine the function of cooling and temperature regulation. HR design and planning for location of UGS Measures of benefits for human population by mitigative effect.
Air quality [18]	Access to air pollution decreases.	Decreases in air pollution near densely populated city areas. Inequitable access to UGS and blue spaces is most significant for air quality, rather than cooling, with migrant communities most exposed to hazardous air pollution rather than urban heat. Spatial equality is an important consider for urban planning.	Variably influenced by vegetative cover, quality and type of UGS, and by distance. Requires measures at a suburb and city level according to air pollution mitigation.	HR Recognising importance of air pollution mitigation, and role of UGS for air quality. ES for future UGS design.
Access, and PGS Walking and various activities [54]	400 m, 800 m, 1200 m. PGS I < 2 ha PGS II > 2 ha PGS III zone of larger size and further away, 1200 m and > 5 ha. Distances are pedestrian distances, and distances can prevent use for children and elderly. Buildings are prioritised in new developments and no UGS are included for the last thirty years. Or only PGS I are. PGS accessibility standard can increase inclusion of UGS in new urban planning and developments, in this case for densification. Densities and limited vacant areas influence UGS types. PGS standards for urban planning are suggested to ensure inclusion of UGS increases with urban development.	Outside of settlement parks and access. Larger parks with measured benefits. Sustainable liveable and healthy neighbourhoods.	Transport other than pedestrian to UGS. Bicycle, public or private transport and pathways and roads for access which make further distances more accessible	ES for PGS types. HR for distance and use.
Mental and physical health [55]	Walking, public transport, bike. No parking as convenience.	Lack of time, distance, no interest. ‘Personal barriers’ as much as distance and institutional. Allergies, untidiness, wild and domestic animals, falling trees and branches, unsafe, fear of getting lost. Having access to private or residential UGS might be. 33 European countries clustered by non-use reasons. Ambiguous other reasons answer, which is open ended answered. Reasons for non-use. [56]	Interest to use the UGS despite standardised measure of access. Transport other than pedestrian to UGS. Bicycle, public or private transport and pathways and roads for access which make further distances more accessible	HR for human health and benefit. Preferences and non-use reasons. ES Functional biodiversity as both aspects of the ESHR concept addresses the findings as a matter of use or non-use of any UGS.
Mental health Optimal benefits and nonlinear links with mental health. PGS, UGSU Provision compared to utilisation Wang et al. [57] greenery effects. We explore the nonlinear pathway: environmental provision → individual behaviour → mental health by focusing on UGS provision and utilization. UGS provision shows non-linear links to mental health, with thresholds for optimal benefits	View compared to interaction by physical visit.	Visibility and mental health compared to active engagement with a UGS. Provision compared to use. Utilisation as measures of benefits. Differentiate between UGS provision (UGSP) and UGS utilization (UGSU) has led to discrepancies between the intended outcomes of UGS planning and the actual health outcome. Practical dosage guidance for urban planners to design green spaces that improve mental health. UGS provision (availability, accessibility, visibility, quality) and utilization (frequency, duration) on mental health, focusing on their nonlinear patterns and thresholds	Viewing and therapeutic benefits. Interest to use. Different uses. Therapeutic benefits are influenced by use. Use and benefit influenced by type of UGS.	ES Environmental provision HR Behaviour, design, mental health as a therapeutic benefit influenced by mitigative effects. Use.
[58]	Simple distance compared to proximity as GIS indicator. Distance as measure on map.	The primary issue to be discussed is how to choose the most suitable indicators to describe the accessibility of people to GS. Proximity measures number of population groups at same distance from a UGS. Simple distance is how far population groups are from a UGS. Distance is the measure of access.	Only about distance, with variance by number of population groups at same distance (proximity).	HR According to distance and ease of access to benefits compared to use. Reliance on distance influences importance of ES but for relevant functions for human access and benefit.
Demographic use. [59] Public perception of urban biodiversity and increases in appreciation [60]	Access as a choice to use, and indicators for access.	Older people less likely to use UGS. Higher education and having children less likely to use UGS. Coutures can be clustered by reasons for not using UGS. Improves appreciation and acceptance even encouragement past exposure effect. Better understanding of urban biodiversity can improve planning. Contribution to quality of life. Recreational benefit, as sensory, visual, etc.	Exposure effects as benefits dependent on choice to use any UGS. Type of use influenced by UGS type and design. Other benefits of access as mitigative.	HR Use. ES Public perception and appreciation can increase ES
A monitoring tool, public preferences and use of UGS [61]	Access measured by use, and type of use.	The indicator development was guided by five principles: ‘citizen based’, ‘functional levels’, ‘preconditions for use’, ‘variety of qualities’, and ‘multiple use’. The parameters were derived from the available research on public preferences and use of green spaces.	Choice to use. Transport other than pedestrian to UGS. Bicycle, public or private transport and pathways and roads for access which make further distances more accessible	HR Public preferences Use can influence complexity and PTSG selection.
Meeting needs of different population groups [62]	Accessibility through various lenses.	Usability, capacity of UGS to meet the needs of diverse populations, imbalanced distribution across a city affecting the urban poor.	Usability dependent on indicator or measure of benefit. Can reach mitigative effects without geographically close access. These effects are influenced by UGS type, coverage and quality. The importance of access to mitigative effects are urban poor or poverty important. Also relevant to sustainable built environment. Transport other than pedestrian to UGS. Bicycle, public or private transport and pathways and roads for access which make further distances more accessible.	HR Use, needs, design for UGS type, responsive to local access needs. ES Quality and type of UGS, responsive to local access needs.

Table 2. Mitigative compared to therapeutic benefit of UGS as measures of access.

Mitigative	Distance	Physical Access	Vegetation, Quality, and PTSG Selections	Therapeutic	Distance	Physical Access	Vegetative Quality and PTSG Selections and Assemblages
Air purification: air pollution	Variable dependent on air pollution	Variable to dependent	Dependent	Viewing	Dependent by horizontal and elevated measures	Variable	Dependent
Cooling: urban heat island.	Variable, by horizontal and elevated distances	Variable to dependent	Dependent	Scents	Dependent	Dependent to variable	Dependent
Noise reduction	Closer to source of noise.	Variable to nil	Dependent	Sounds	Dependent	Variable	Dependent
Non allergenic selections for pollen	Dependent to variable	Variable to nil	Dependent	Physical activity in UGS	Dependent to variable	Dependent	Variable.
Vegetative density, and urban canopy cover	Variable to dependent	Variable to dependent	Dependent to variable	Transparent spaces, Aquatic spaces bathing, sounds, cooling	Dependent to variable	Dependent	Dependent.
Measures of access
Access	NDVI Densities and distributions	Availability and accessibility by distance		Vegetative densities fifteen classification, and location of each density
	Proximity and simple distance			A comparison of population size by simple distance comparisons. Simple distance is the number of people at each distance from any UGS	Loss of private UGS rarely seems offset by provision of more public green space. Several ways are identified to deal with these challenges, while also highlighting research gaps, e.g., as to how loss of green space quantity can be offset by increased green space quality [31]
	Utility			Functions of any UGS type, recreational, sports, playground, paths, gardens, urban agriculture, forests, aquatic, pools, ponds, creeks, rivers. Safety and comfort. Demographics likely to use UGS
	Mitigative and therapeutic			Access to mitigative effects, and therapeutic benefits	Influences of distance and quantities compared to quality and size
	Accessible transport			Bikes, walking, car, public transport

Table 3. Specific benefits of UGS location and type on air, water, sensescape, therapeutic, environmental and ecological.

Benefits
Air	Noise mitigation	Distribution of green space near the noise source can effectively prevent noise propagation. [63]
	Particles	Air purification from pollutants
	Pollen	Wind compared to pollen pollinated. Allergenic pollen emissions as significant to air pollution and risk to human health. Native and wild pollinators, compared to introduced species for nonnative wild and non-allergenic Pollen emissions are negatively impactful to human health. Access to UGS can result in negative impact as exposure to allergenic pollen
	PM2
	PM5
	O3
	Microclimate and cooling	Heat radiation from built environment, different UGS types and vegetative densities provision different microclimates and cooling effects. Different urban landscapes require urban cooling, and respond differently to UGS for cooling.
	Light	UGS can regulate and influence light exposure, as UV exposure or sight
Water	Purification	UGS of varying types can provide a purification function for water
	Cooling	Urban heats influence on urban water temperatures
	Vector borne and zoonotic	Higher risk of disease with increased coverage
	Oceans	The preventative function for water quality can influence ocean water quality influenced by urban water
	Pollutants	UGS of varying types can provision various preventative functions for water quality as a capture or filtration function
Sensescape	Scents	From any UGS type, in addition to air purification function
	Sounds	Quieter environment; Sounds from taxa and vegetation
	Cooling or humidity, microclimates	Microclimates as influential sense of comfort
	Colours and visual stimulus	Proven as therapeutic
	Sunlight and shade	Influential to comfort; needs for UV light
Therapeutic	Mental health	UGS of different types and exposures, physical access, viewing, sensescape access, access to benefits of mitigative effects are proven to improve and prevent the three examples of health conditions provided
	Hypertension
	Respiration
Environmental and ecological	Healthy ecological interactions and processes	Anthropogenic effects Global meta-analysis reveals contrasting impacts of air, light, and noise pollution on pollination Functional ecological interactions and processes for various vegetative densities and UGS types are indicative of a healthy natural-environment PTSG selections and assemblages are influential to functional biodiversity as healthy ecological interactions and processes.

Table 4. Different definitions of UGS used by various articles, and measures indicative of access, function, and benefit.

1	[31]	Urban gardens and forests; urban agriculture; urban green rooftops, walls, ceilings, urban green corridors. Urban parks, forests, gardens	Functional biodiversity and RW
2	[39]	Urban forests compared to urban tree canopy	Stratifications and canopy compared to lower layers. LiDAR, biotope, S-API, and I-tree.
3	[44]	Urban biodiversity. Wild refined urban greenspaces	Smart cities integrating functionally biodiverse UGS using RW
4	Constructing a definition of UGS [64]	Greenspace and green space. Need to define green space explicitly, whereas green infrastructure assumes and works with intended outcomes without clear definitions	Measures, effects of Greenspace and interactions with the natural-environment. Indirect, incidental and intentional Plan and perspective view. Perspective view: green view, NDVI, LULC, Tree canopy cover. Green view index, LULC and digital terrain models to calculate observation points. More observation points than trees. Plan view: calculate UGS from above as distribution of vegetation for exposure. NDVI, geospatial data, and satellite imagery. WorldView-2 [65], Landsat 5 [66,67] and Sentinel-2 [68] Tree canopy cover: area covered by trees	ESHR, views and vegetative composition.
5	Spatial inequality in exposure and urban nature, and air pollution and UHI. Oslo, Norway. [19]	Blue-green spaces in cities, often referred to as ‘urban nature’ or ‘blue-green infrastructure’, are the multifunctional, predominantly unbuilt spaces that supports both social and ecological landscape settings and processes [43,44,69] Operationalized as parks, forests, street trees, gardens, playgrounds, rivers, lakes and oceans, blue-green spaces provide a range of services to society, not least of which include the mitigation of exposure to environmental hazards such as air pollution and extreme temperatures.	Densification Urban Greenspace NDVI Blue space: Euclidean distance to water body Need for intraurban blue green space
6	[70]	Green space determined by measures or grass, trees, edges	Improvements in UGS access measured by remote sensing.
7	[71]	Urban greenery as Lawns, trees, shrubs and flowerbeds	Use of geoinformation models to Minotaur and manage UGS
8	[72]	Urban greenery	Urban expansion and crop land loss leads to further importance of urban greenery
9	Under appreciated contributions [73]	Vegetation cover and land use and cover change for air quality	BVOC, O3, VOCs, NOx Air quality MDA8 UGS-BVOC UGS-LUCC
10	[74,75]	Plant carbon sequestration and carbon density. Green spaces associated with various urban development sites. Three categories, regional park, neighbourhood park and attached green space	InVEST [76] and I-tree model Plant community complexities positively associate with carbon density. the selection of tree and shrub species and planting density partly influence the overall carbon storage capacity of these communities. In future planning and design, plant species with higher carbon storage capacity should be prioritized to enhance the community’s carbon storage. Neighbourhood parks have highest carbon densities and storage. Mitigation for climate change, counteract fossil fuel emissions.
11	[77]	UGSs such as parks, street greenbelts, community gardens, forested patches, and green rooftop. Urban vegetation, trees shrubs, and herbaceous cover.	Improve air quality, mitigate the urban heat island effect, reduce surface temperatures, and absorb harmful pollutants like sulphur dioxide and nitrogen oxides [78,79] In particular, UGSs play a significant role in public health, supporting physical activity. UFU urban functional units compared to UGS. Land cover, trees and shrubs, herbaceous vegetation cover. Increases or decreases in UGS within UFUs, as compared to land cover and increases and decreases.
12	[68]	Fifteen classes of urban greenery measured by sentinel-2A.	Urban forest/uncultivated park; cultivated park; cemetery; urban public garden; stream bank/lake shore vegetation; urban greenery in apartment housing areas; urban greenery in public facilities; greenery in sports facilities; complex cultivation pattern; crop land/pastures; railway and roadside greenery; green areas in industrial units; airport greenery; ruderal vegetation. No signs of recent cultivation. Tree vegetation provides wider functions. Urban tree canopy.
13	[80]	UNESCO listed, low and high quality UGS.	Ecological and landscape service levels are measured.
14	[81]	Per capita Park green area.	Health level of residents. The results of this study have confirmed that the health-promoting effect of green spaces varies individually and regionally. If the inhabitants have a good state of health, green space has a significant health-promoting effect; if the inhabitants’ state of health is poor, their health level is not affected by green spaces. In addition, the response of green spaces to health varies between provinces with different climatic backgrounds. The health level and the per-capita park green area of the residents of mid-temperate and warm temperate regions are related, and increasing the park area in these regions can effectively improve the health status of the residents. The health level of residents in subtropical regions is not affected by the per-capita park green area. Therefore, it is necessary to develop reasonable UGS planning strategies based on the health level and climatic background of residents in different provinces, especially in areas where residents have a better health status, and to further utilize the benefits of promoting health through UGS.
15	[57]	Urban greenery. Lawns, shrubs, trees and green walls.	Integrate top–down (using the NDVI metric), eye-level (using the GVI metric), and spatial (using the LVV metric) dimensions to comprehensively measure UGS greenery; (2) employ systematic observational tools (the SOPARC and SOSIP) to objectively capture both physical activity and social interaction across all age groups, thereby offering a holistic perspective on engagement in health-related activities in UGSs; and (3) explore the associations between multi-dimensional greenery measurement and multi-age health-related activities, thereby informing effective planning strategies to improve the quality of UGS greenery for promoting inclusive public health
16	[82]	Vegetated urban land. rapidly urbanising cities, where urban planning models often fail to adapt to the expanding population and do not adequately consider which groups are at risk due to their lack of access to UGS [7,8]	Private and public parks, including small water bodies like ponds, lakes, or streams. Cultural ecosystem services as intangibles. Improving quality of life. Accessibility through various lenses. Usability, capacity of UGS to meet the needs of a diverse population.	ESHR
17	[83]	Definition of UGS adopted in this review encompasses both publicly and privately owned land, sometimes an important distinction in relation to sustainability and equity aspects of green space [80]	Less area per person due to compact and densely populated cities. Ensuring that all green spaces are vegetated and pervious to the greatest extent possible would be a good first step. So would ensuring the judicious provision of small green spaces and street trees in intensifying areas. There are many uncertainties in addressing these challenges within AoNZ’s rapidly changing planning system amid the urgency of addressing long-standing deficiencies in other areas of urban infrastructure. One of the most important challenges is ensuring that urban biodiversity and the habitats of that biodiversity are integrated into the infrastructure and planning for other priorities and not set aside as lower priorities.	HR
18	[84]	Natural open spaces containing trees within built-up areas including parks, street trees, urban forests, residential lawns, and rooftop gardens	Women’s preferences for UGS types and uses of UGS. Among these pathways, time, security, and PSFs have the most significant impact on women’s preferences. It is anticipated that this study will bring greater attention to caring urbanism and foster dialog in this field among urban planning and design researchers and policymakers, particularly in non-Western and developing countries.	Human realities
19	[14]	Public parks and green metrics about trees, multilevel greenery. Earth observation and statistical data. High socio-economic demands. Tree demands do not align with environmental pressures, LST and pm2.5	Per capita, supply and demand and equity, green supplies and human demands, shorter distances.	HR
20	[58]	Green spaces as any urban space with vegetation.	Accessibility, quality of UGS. Lower than WHO recommendations and recommendations for increased access by paths and roads. UGS can give feeling or effect of socialising from walking or sitting spending time in them. Even with just a view of them. Tree canopy cover and distances of vegetation spaces of various sizes from urban population by walking 300 m 5 min walking. Three categories of vegetation or green spaces. Parks and gardens, wooded, wooded agricultural areas.	HR
21	[85]	Green spaces in urban areas, public parks and woodlands to gardens	Human health and wellbeing. Use and health [86,87,88].	HR
22	[37]	UGS as any type of vegetation. Green space patches and density Vertical and green walls and rooftops, pocket parks, micro green spaces.	Small scale green spaces in densely populated areas, and importance of urban planning, long term land use changes, compared to short term studies that are available. Edge density, area and shape of patch [83] and edge of landscape ratio. Spatial inequality between 1990 and 2020. Three major regions with development strategies for 2049, and different measured inequalities for each region. Planning to reserve green spaces and include wetlands and blue spaces.	Niches, small scale and maybe connected green spaces in densely populated.
23	[59]	Indoor and outdoor, wild nature, pocket park, wetlands and other features.	Quality: elements that determine value and desirability including aesthetic attractiveness, utility and ecological diversity. Quantity amount or extent of greenery in specific geographical locations, indoor and outdoor, wild nature, pocket parks, wetlands, and other features.	ES HR Functional
24	[89]	Vegetation in urban environments. Parks, squares, residential gardens, street trees.	Urban ecology: UHI, air purification, lowering surface runoff, biodiversity, carbon storage, maintaining ecological balance.	Functional
25	[49]	Green zones surrounded by urban development, accessible to the public and contiguous natural vegetation, of unique character. Managed and designated parks and recreational spaces accessible to the community and adjacent to build up landcover.	Suggests limited trade-offs between biodiversity and human utility. Design and utility must accommodate biodiversity conservation. UGS types that provide synergies include positive correlation between some attributes such as playgrounds, bodies of water, nature preserves, and dog parks with biodiversity, indicating potential synergies rather than trade-offs.	ESHR Functional urban biodiversity, functional design, advanced function.
26	[38]	Vegetation cover and definitions of UGS and urban forests	NDVI Urban forest definitions UGS types. when grouping UGS by function, if all vegetation areas measured by the NDVI are classified as UGS, questions emerge about whether private lands or inaccessible urban forests should be included.	HR, ES, function by public access.

Table 5. Thirty-eight UGS types found in the reviewed article, descriptions, and appropriate urban development.

UGS Type	Description	Urban Development Type
Urban forest	Different definitions. Human impacts on an urban forest, urban tree canopy, a forest like UGS in an urban area.	Surroundings Urban centre as small scale stratified and densely vegetated UGS Urban trees and urban tree canopy.
Urban tree canopy	A canopy of urban trees that connect across an urban landscape.	Across an urban landscape. Densely vegetated with trees is dependent on the UGS and urban landscape type.
Urban agriculture.	Productive system, with various reasons for productive activity	Surroundings, and as small-scale community gardens.
Urban Park	Urban forest, recreational green space, or grassed area for public use.	Recreational grasslands, forests, and vegetated areas. Size and function dependent.
Gardens Residential, community, public, rooftop, wall, and ceiling.	Enclosed areas adjoined to buildings of various sizes dependent on the country defining it, with various intentions for connection with the natural-environment and various intentions for human use. In most cases they are designed.	Intra urban centres, surrounding areas.
Residential gardens	Private green spaces adjoined to a residential building.	Any urban settlement.
Grassed	Any UGS type and size with grass.	Any urban settlement and any size.
Meadow	Wild and native grass and flowers.	Any urban settlement and any size.
Public gardens	Different sizes for different urban development types.	Intra urban centres, or surroundings.
Urban green roof	Densely populated, built-up areas, and or for any built environment.	Densely populated vertical expansions in built environments requiring elevated UGS. Built up urban developments that require green coverage for UHI mitigation.
Multi functional urban open space with greenery [90].	Any type of greenery in an open urban space.	Urban centres, public places with greenery.
Green corridor	Green space that connects different UGS. Connectivity functions. While corridors are most designed and established for connectivity function, RW proposes that all UGS can have the same function, with corridors purposely connecting different UGS. Where all other UGS can be designed, located and established for connectivity function as a landscape functional outcome.	Small scale urban greenery of different shape, longer narrower shapes that connect different UGS.
Ecotones and edges for ecological niches.	Green overlapping areas between different UGS, and different vegetative densities.	Ecological corridors and intra UGS systems. Any UGS size, and for high density green cities.
Micro green space [91,92]	Densely populated. Individual efforts	Densely populated urban centres
Green seams [91,92]	Individual efforts.	Densely populated
Pocket parks	Small size	Densely populated
Conceptualising green [64,93]	Twenty-three different natural areas in city and regional areas that are green concept, of forty-three natural area types. Connecting green spaces of natural-environment from urban centre to green belt or that run in different directions and are recreational. Green fingers, mittens, and rings [94].	Densely populated country and city.
Green belt	Green space of natural-environment around an urban centre and surroundings, and between urban centre and suburbs, or sprawl.	Horizontal expansions.
Fifteen classifications of NDVI [95]	Vegetative density.	UGS integrated human settlement
RW and wild refined UGS [31]	Gardens: Urban agriculture Urban green rooftops, walls and ceilings: Urban green corridors. Where all other UGS can be designed, located and established for connectivity function as a landscape functional outcome.	Any urban settlement.
Urban forests, stratified PTSG systems. [39]	Regional definitions, European, urban greenery, gardens, promenades (walls and canals), tree lined paths, walls, street trees, public gardens, allees. American and Canadian: urban settlements in dense forest and impacts of human settlements. More recent definitions and uses of the term: Urban tree canopy, urban trees, any UGS, urban greenery, peri urban forests.	Intra urban and peri urban forests, by varying definitions.

Initial Findings and Conclusions

The examples of importance given to access to UGS, and the various functions of UGS, prove an access definition that specifies UGS type, access by coverage and distance, and also utility as influential to determining optimised spatial planning. The two categories of benefits from access, mitigative effect and therapeutic benefits, further understanding of why access is a frequently studied aspect of UGS integration to urban planning. The definition of UGS proves to be an important consideration for utility and the two categories of benefits. The conceptual guidance for analysis and for urban planning, refined wilding, integrates and ensures consideration of ecological interactions and processes, at UOS, and landscape levels, and of human realities to ensure landscape-focused, relevant and realistic UGS integrated urban planning, results in long-term outcomes. Long term outcomes are expected with realistic plans for maintenance and management, which are influenced and determined by aspects of the refined wilding concept, wild PTSG selections and assemblages for semi-natural UGS systems and landscapes by functional connectivity across UGS systems, UGS type selection and spatial configurations that optimise advanced functions of all UGS in an urban landscape, and positive influential flows between UGS, transparent spaces and grey spaces. The optimised outcomes of sustainable building, combined with advanced function UGS, are an example. The definitions of UGS and measures provide further consideration for informing urban planning that leads to implementation and long-term outcomes that address not only the more challenging issues of urban heat and air pollution, but that can also provide equitable quality of life without resulting in a push to horizontal expansion and sprawl by population moves, and gentrification.

2.5. Summary of Tables and Findings

2.5.1. Table 1

The standardised measure of distance does not encompass access to all benefits of UGS and therefore introduces the important consideration of benefit without close or minimum coverage reached. That is a benefit beyond standardised understandings of access. This, in turn, leads to further defining access to UGS past minimum coverage and distance. La Rosa [58] discusses how accessibility to green spaces requires a suitable choice of indicators. From this table, benefits are qualified or categorised as mitigative effects and therapeutic benefits resulting from use, and even mitigative effects. This takes indicators and defines access past proximity and to an important measure of provisioning. It introduces the importance of optimised and distanced benefits of different types of UGS, which are measures of access. The ESHR concept encourages functional biodiversity through ecological interactions and processes with a balance and reciprocal interdependence with human realities. Some of these human realities include access to resources, knowledge sets for design and implementation, city and country circumstances, including existing UGS, quality of the environment, access measures, human behaviour and use of UGS determined by demographics of age, gender, general health of the population and culture, as examples. RW is a substantiating concept for functional biodiversity and analysis using it provides a basis for findings and strategies for urban planning that are explained.

2.5.2. Table 2

The consideration of distance is as important as proximity, but compared to provisioning from surroundings, it limits an understanding of UGS access. Access to functions as benefits can be irrelevant to the distance of a UGS but influenced by the UGS type and quality, and coverage is still a significant influential factor for access to UGS benefits.

2.5.3. Table 3

Examples of numerous benefits of UGS by provisioning and proximity are summarised. It also emphasises the negative impacts of human activity on the natural-environment and on different UGS types. Supporting the initial definitions of urban forests in the USA and Canada, as human impacts or urban and human activity and human settlements on forests, as compared to urban forest definitions from Europe as greenery, trees or grasses, gardens as examples, in urban landscapes.

2.5.4. Table 4 and Table 5

UGS are most frequently referred to as urban greenery in any given article, with the study’s aims and questions determining the specifics of the UGS studied and the relevance of recommendations. The measures used also lead to how UGS are defined and referred to. The 38 different UGS types presented in this table provide different benefits resulting from different functions.

2.5.5. Summary

The categories of access to benefits of UGS, mitigative effects and therapeutic benefits are to optimise UGS integrated urban planning, particularly for densification and avoiding the negative outcomes of sprawl, which are significantly influenced by UGS type. Examples of the different functions include recreation, environmental services, cooling, air purification, aesthetic benefits, physical access and interaction, and additions to pervious surfaces for improved cooling. The size of the UGS is determinant to functions, and in some cases benefits, dependent on quality and can lead to transport facilitation over increases in physical coverage as access in inner city landscapes. Their selections and spatial distributions, and their type by size and functions provisioned, are significantly influential to the benefits provisioned and expected. The UGS types selected for inner city, particularly densified urban developments, will be different to those in suburbs and city surroundings. The benefits from access for inner city, and different inner-city landscapes to UGS, compared to benefits from suburbs and city surrounding UGS are different, and measures of benefits already accessed can accurately inform urban planning for UGS selections and spatial configurations. They can also improve spatial understanding of UGS types and configurations for urban planning that ensures functional connectivity between existing UGS in different inner and surrounding city landscapes, and plans for new UGS. UGS integrated urban planning for any urban development, densification, sprawl redesign or suburbanisation, and improvements in UGS can more accurately identify benefits accessed and needed, ensuring reserve of UGS instead of losses, and even increases, and then increases in UGS quality and in the quality of green urban landscape, as green infrastructure, micro green spaces, pocket park, elevated greenery options for densification and high-density cities, as compared to large size UGS for recreational, sport, environmental reasons, and residential gardens for horizontal urban developments, are an example of differences that can better inform urban planning and inclusion of UGS.

3. Findings

Urban planning can be informed and influenced by organisational minimums and recommendations [1,2] but must also be informed by advanced and specific studies, and landscape-specific circumstances and factors. An example is the understanding of access to UGS. While Integration can be along frequented locations, for increased exposure [65,66], access to all benefits might not require this type of exposure. This article suggests that access to the benefits of urban greenery could optimise urban planning for the advanced function of urban greenery and urban landscapes and improve an understanding of access. Functional urban biodiversity measures can include how functions are measured as access to benefits varying by distance, size, quality, function type, and UGS type, determined in part by standard intentions or measures of positive outcomes for different functions, and by system or space level, then at a landscape level as connectivity between different UGS types, and between different UOS types, including transparent and grey spaces, Table 6. Functions as an informative measure of benefit and indication of access to UGS lead to refined wilding for functional urban biodiversity as a concept and principles for UGS. It is conducive to measures that can inform urban planning.

Table 6. Categories of Urban Open Spaces.

Urban Open Space
Gray space
Natural-environment	Built environment
Green and transparent spaces	Grey space

The functions required as categories of benefits from access to UGS are mitigative effects and therapeutic benefits. From a point of access, mitigative effects and therapeutic benefits are accessed with consideration of the provisioned. Or from a function’s point of view, UGS selections, and spatial configuration are guided by refined wilding intent for advanced function and will therefore provide benefits. Where guiding urban planning, wild refined UGS will provision appropriate and needed benefits for the urban landscape, and will be selected, spatially configured and functionally connected for and across the specific urban development. The mitigative effects of UGS are most commonly identified as carbon sequestration dependent on vegetative density, urban heat mitigation as urban cooling, and transparent space (air and water) purification or decreasing (air and water) pollution. Therapeutic benefits are significant for urban landscapes, as human health is proven to benefit from UGS and, more importantly, to be negatively impacted by urban landscapes, air pollution, urban heat, extreme weather, and, less obviously, by some aspects of the natural-environment. The therapeutic benefits of UGS can also be less obvious with sensescape functions, and viewing proven to improve different health conditions and prevent risk factors for serious disease. Refined wilding ensures a consistent consideration of natural-environment, functional ecological interactions and processes, and of human realities for urban planning, past the benefits to access, for wild PTSG selections and assemblages, landscape functional connectivity, optimised spatial configurations and advanced functions.

3.1. Access to and Definitions of UGS

The utility of each UGS, actual use, and measures of access by benefit and function more specifically describe what UGS access more practically means. Urban planning could then ensure integration of UGS by these more specific measures of UGS and access to encourage an accurate measure of benefit and improve urban planning and implementation of the advanced function of UGS. These factors of benefit can also address the finding of inequitable access for lower socioeconomic groups, compared to the benefit of the mitigative function.

3.2. Access to the Benefits of Different UGS Types: Mitigative Effect and Therapeutic Benefits

In most cases, distance is the determining factor for access to UGS, with various positive functions and benefits of different UGS types further influencing the benefit of access that goes beyond distance. Indicators of mitigative effects, cooling and air pollution, and then therapeutic benefits can further define and measure access to UGS. The WHO recommendation for at least 0.5–1 ha of public space within 300 m of their home [1,2] is most often for urban heat and air pollution mitigation. Venter et al. [19] prove a different mitigative effect for the two risk factors of air pollution and urban heat from UGS, and a subsequent variance in need for UGS access for each reason. The importance of integrating urban greening with sustainable built environment developments, as passive or other sustainable building principles, is seen and proven as mitigative for urban heat. With pervious surfaces, sustainable building and greenery proven as mitigative [90] and greenery variably effective for cooling, dependent on each of the five urban zones. For residential zones, greenery by vegetative cover can have significant mitigative effects for cooling and is often recommended for urban planning that accommodates population increases; other zones require permeable surfaces and sustainable building design more than greenery. While these mitigative effects of UGS are most often motivators for urban planning and development inclusion, the other positive impacts of UGS can lead to an improved understanding of access and of good planning for urban biodiversity. These studies lead to findings of variable distances, and then, the variable UHI compared to the air pollution benefit is influenced by spatial distributions and planning of UGS. Then, the considerations of access compared to use, with various measures of view compared to interaction, accessibility indicators and accessibility by choice to use. Some studies indicate that the choice to use is limited and different by age and gender, that lower socio-economic populated areas of cities are lower in UGS and impacted by air pollution because of it, and not by UHI. The design for utility, compared to general definitions of access, is also relevant to a need for more specific consideration of access for urban planning that integrates UGS. Access is therefore most generally recommended as minimum coverage, with distance from human populations also measured.

3.2.1. Different Functions of UGS: Mitigative Effect and Therapeutic Benefits

From the articles selected about access and different benefits, two categories of benefits are identified: mitigative effects and therapeutic benefits. They are provisioned by UGS access and address the most sought-after and proven positive functions of UGS for urban landscapes. Benefits from access are therefore understood as different functions provided by UGS.

Renaturing, in particular, focuses on mitigative and urgent responses provided by UGS. Therapeutic benefits are newly studied and are significant. The benefits from the two categories are UGS type, quality and distance dependent. In some cases, distant large UGS forests or parks might provide therapeutic and mitigative benefits effectively with improved measures of effect and benefit. The benefits of access are dependent on specific functions of the UGS and are influenced by other factors. Connective UGS in urban centres might then be required, with specific benefits required as a matter of optimising and providing advanced function. The two categories are measures of access to UGS. They vary by coverage type, quality and functional connectivity. Urban planning that integrates UGS and optimises understanding of the intended benefit and aim of integrating UGS can then ensure the minimum coverage and distance from home, minimums and recommendations are followed, alongside the benefits of access measured and needed, to determine the need for increases in UGS. The maintenance, improvements and increases in UGS coverage are then planned with importance given to intended and needed benefits. These intentions and needs will then be influential to UGS selections, spatial distributions and configurations for functional connectivity and advanced function. Therapeutic effects are influenced by or can easily combine with mitigative functions, whereas recreational use can depend on the size of a UGS and is significantly influenced by the urban development type. The various aspects of just planning for urban greenery are also relevant for planning, compared to implementation, with opportunities to improve existing plans for urban greenery when not implemented with built urban development plans, as has been the case for densification [12] and for high-density cities that require maintenance or increases in urban greenery [91,92].

Optimising UGS integration and inclusion requires strategic planning that goes past assuming access by coverage is sufficient [95] with ecological knowledge suggested as almost as essential for appropriate functions from UGS [69,80]. This article brings attention to the definition of access, and to benefits as mitigative effects and therapeutic, with RW for functional urban biodiversity encouraging human realities for planning and implementation, maintenance and evaluation that can ensure functional ecological interactions and processes of any urban biodiversity, at urban green and transparent, even grey space levels, and landscape levels as functionally connected.

3.2.2. UGS Definitions

In most cases, UGS are greenery adjoined to buildings or paved areas. They have various functions, including connectivity between UGS, corridors, personal and private indoor or outdoor residential spaces, gardens, recreational areas to enjoy with other people, public parks, gardens and open green spaces, open green and transparent spaces that serve mitigative functions of cooling and air purification, urban trees, parks, green rooftops and walls, micro green spaces, urban forests, wetlands, ponds, rivers, creeks, ocean. Table 4 lists the different definitions found in articles reviewed, with a description and urban development type for which the UGS type is most appropriate. The measures of NDVI imply density measures of vegetation and fifteen UGS types. In more specific studies, such as urban planning for densification, particular UGS types are more common. The different UGS types studied in reviewed articles from the first search results, Table 4, are most commonly referred to as urban greenery. UGS definitions and from the first ProQuest search result list, thirty-seven definitions of UGS types, Table 5. There is variable specificity in UGS definitions, while measures of access are standardised by NDVI, vegetation densities, I-tree measures, and accessibility of coverage and distance, and most refer to urban greenery of varying densities. There is not much specificity in taxa functions, and varying specificity in vegetative densities, stratifications, and diversities. The different UGS types are listed as appropriate for particular urban developments and give an example of how the different UGS types could be better specified and used for particular urban development types. The different UGS types also provide improved specificity for RW guidance, as expectations for vegetative complexity and function, human use functions, and access to benefits. Language and definitions of UGS are influenced by indicators and metrics and measures by LiDAR, Sentinel, NDVI, as well as vegetation density and tree canopy, and then by recommendations of access by coverage and distance. The various definitions of UGS found in the literature searches indicate measures of vegetation and greenery as the most common. Further defining terms like parks and trees is also most common. Vegetation density and tree canopy can be furthered by RW wilding with ecological functions, and human realities of each vegetation and tree canopy cover are measured and planned for according to an intended use.

A UGS type selected for the suburb level, and for landscape level functional connectivity, while also fulfilling and optimising access and benefit categories for the urban landscape, can be informed by the factors of access and need at local levels. Different UGS types can suit the urban development to avoid sprawl without requiring more UGS or requiring UGS for a specific benefit. The UGS must then be designed and spatially planned for the benefit needed, for maintained benefits, and then for any optimised outcomes resulting from the advanced function of urban biodiversity. The optimised benefits of blue green spaces for cooling, and PTSG, and vegetative densities and selections for air purification and limiting allergenic pollen emissions are examples of factors for each mitigative effect. The UGS type selected is an additional consideration, alongside how existing surrounding larger-sized UGS might already be provisioning mitigative effects and or therapeutic benefits. Then, how are newly established UGS functionally connected and are located across a landscape of different UOS, green and transparent urban spaces.

3.3. Different UGS Types and Functional Configurations

Discussions of urban forest definitions and the history of the definition [39] measure the impacts of human activity on the natural-environment, compared to UGS in urban landscapes and benefits for human populations. These measures also provide further reason for maintained and increased UGS through a densification and sprawl redesign process, and any horizontal urban development plan and implementation, with the impact not only on human populations but also on surrounding and existing UGS quality. As the impacts of climate variations, urban heat and air pollution have an effect on human and natural-environment health. The effect of urban heat mitigation and air pollution reductions is also height conditioned, with street level, compared to elevated greenery, measured and indicative of different mitigative factors. The ecological complexity and PTSG selections are also influential to mitigative functions, and other functions provided, as well as the UGS type, as recreational, paths, near or containing water, UGS size and distance, private or public, are influential to use, and balance between biodiversity and human benefit. These factors are influential to access, appropriateness for densification, as compared to plans for redesign or new horizontal developments. Redesign is for the existing built environment and even for already designed or used natural-environment spaces, and is part of urban planning processes. This redesign is also referred to as retrofit [96]. Most UGS in urban landscapes are designed, with the exception of urban development around a natural environment. The impact on the natural-environment of unorganised urban development leads to rational recommendations for planning urban developments, particularly developments that result from population densities and demographic differences. Measuring UGS for the impact of human activity as compared to having to design and plan new UGS to compensate for fragmentation of the natural-environment, and to care for the human population directly, and past caring for the quality of the natural-environment, is a preventative strategy and measure.

Functions and Distance

Table 7 presents findings relevant to benefits from different UGS types for different demographics. It presents the access as a benefit to mitigative effects and therapeutic benefits in the right column as examples of findings relevant for urban planning that optimise UGS integration. RW is then the conceptual guidance for UGS selections, connectivity to ensure advanced function past the optimisation of access to the benefits of UGS.

Table 7. Examples of UGS access for urban planning.

Time of exposure Elevated and horizontal distances from human population. Size of park Land suitability Synergies between biodiversity and human activity Indicators of access Protect communities while increasing UGS Shorter distances Optimising use with biodiversity

Good walking environments and accessibility for wellbeing. With better measures of outcomes closer to the time of UGS exposure [87] Elevated UGS have variable levels of cooling and air purification effect for pedestrians compared to residents or occupants and are not always as easily visible or for viewing. External green walls, UGS at pedestrian level, compared to rooftops. Large parks found with higher correlation to perceptions of discrimination by marginalization and negative impacts on mental health for migrant populations, rural to urban in the study case. Smaller parks facilitate social inclusion and improve mental health. Quantity stronger correlation to positive mental health, but by small park size [59] Land suitability for UGS, average distance from UGS by land suitability, low suitability can still include UGS [89] Positive correlation between some attributes such as playgrounds, bodies of water, nature reserves, and dog parks with biodiversity, indicating potential synergies rather than trade-offs between biodiversity and human activity and use of UGS [49] A need for focusing on conserving UGS and optimising access and function of access, as indicators of access. Urban greening can, however, create paradoxical effects such as gentrification. UGS projects need more integrative sustainability policies to protect communities [88] Shorter distances from urban parks are for elderly and children [14]. Optimising for sports, recreation and interactions with nature ensures experiences interrelated and distinct health benefits from greenspaces [48]

Time of exposure [56] can be relevant to close by proximate or further away populations. Access and facilitating access by distance and coordinating public and private transport, paths and roads can increase time of exposure. Exposure is also a measure of benefit from access, other measures of time of exposure can include the categories of benefit from access. Densification requires elevated and vertical, even micro green spaces according to coverage and distance minimums. Pedestrian level UGS of different types have different impacts on air quality, some negative impacts by allergenic pollen. Large urban parks which present negative socialising effects might provide positive mitigative benefits and other therapeutic benefits. The findings associated to access as benefits in these categories can better explain and organise use of different UGS for more comprehensive and positive impacts. Air purification and cooling function of large surrounding parks as accessible to urban centres is an example. Minimising allergenic pollen emissions by distance of different UGS is another example. Land suitability introduces another factor for quality and benefits from distanced UGS rather than UGS where land is not suitable. Encourages a physical access and use through design and UGS type of any UGS, as urban biodiversity requiring synergy with human activity. Two categories of benefits of UGS are influential to optimising access, as a function of access. The measure of exposure and access to benefit can ensure a UGS is not introduced where it might cause gentrification. Proximity and distance as access for use is variably proven for elderly and children with other societal factors influencing their use of any UGS. Design of UGS optimised for use with biodiversity can improve benefits for distanced and non-users with functional biodiversity integrated as nature.

3.4. Existing Recommendations and Findings

The analytical process and findings applied to urban planning, particularly for densification and other urban developments that avoid sprawl, lead to suggestions for required improvement for UGS integration for urban planning. Improved definition of access, as access to the two categories of benefits to UGS identified alongside the different definitions and types of UGS has given findings that address some existing findings. Table 8 presents the examples.

Table 8. Examples of existing research addressed by findings.

Implementation compared to UGS integration to urban planning.	Planning after implementation Planning for greenery in urban landscapes is not implemented [29]. Evaluating the use of implemented plans and implementing already planned greenery for use after considering next to use.
Planning for long term outcomes from UGS.	Ensuring good design, RW and implementation to ensure long term outcomes. Examples of urban tree selections for function and maintenance [39].
Balancing the benefits of access needed with minimum requirements for access.	Minimum coverage [1,2] with access to benefits needed.
Planning, designing, implementing and evaluating for advanced function for benefits from access.	Advanced function for ecological interactions and processes and human health, mitigative effects and therapeutic benefits [31].
Improving measures that inform urban green planning for densification, and horizontal redesign to avoid sprawl and ensure needed benefits from access to UGS are achieved.	Evaluate existing urban landscapes at local and city levels for built environment plans, and greenery for intended benefits from access [5,17,90,91], including cooling and LST regulation [92,93,94,95,96].
RW design and urban planning could more easily motivate advanced function from UGS as conceptual guidance for significant motivating factors for designers.	Conceptual guidance for motivating factors for designers [40] intrinsic to external factors.
Urban population increases requiring built environment vertical and horizontal expansions.	Avoiding sprawl with densification and redesign of sprawl, grey and grey spaces, and for densification. Ensuring appropriate urban greenery for the urban development. Densification: Micro green spaces, elevated green spaces, corridors, vertical walls. Sprawl: Redesign with residential and public greenery of various types. Suburbanisation: Improved quality in residential and public UGS. Grey and gray spaces: Redesign with high quality advanced function for landscape connectivity combined with public place uses, or residential use.

3.5. Questions to Ask for Sustainable Urban Planning

Demand and value for urban greenery can be higher in inner city locations, particularly high-density cities, where services are provisioned and proximate, but greenery is not. In suburbanised urban areas, greenery is often provisioned and proximate to services in demand and in low supply. In some cases, high-income countries have lower socio-economic populated areas that require UGS for air pollution mitigation but not for urban cooling [19]. These specific city-level examples prove urban planning for local circumstances, high-density or suburbanised areas, while balancing with international data and recommendations as significant for any standards for UGS and densification strategies in urban planning and implementation. A summary of different factors influencing access and the need for consideration of different ideas of access. Other influential factors include the ideas of the quality of UGS. For urban forests, various factors are studied aspects of quality, including aesthetics [36], which are measured as attractiveness [84] and sustainability, which considers a range of benefits and costs, with connected factors of utility and use as influential to ratings or measures of access. Functional ecological interactions and processes, and assemblages for any UGS type, and landscape functional connectivity is another consideration, with access to various functions provisioned as benefits factored in. The questions to ask for urban planning are the following:

• What benefits are already accessed from the surroundings compared to close-by UGS, larger parks, micro UGSs, and corridors?
• What specific benefits are needed by nearby populations from inner city UGS?
• Can improved transport to surrounding UGS address use, while other UGS types in closer proximity address the mitigative effect and other therapeutic benefits.
• Can the two categories of access improve measures of benefits from UGS, and more accurately satisfy what is sought from equitable access?
• Can the two categories of measures of access better address the benefits of distant populations, like air purification or cooling, or physical use, leading to improved understanding of benefits needed for inner city, and optimised planning?
• Can functional biodiversity better frame the measure of benefit from different UGS, and guide the measure of access to benefit?
• If urban plans do not adequately integrate UGS or implement for optimised outcomes, can a standard for UGS help? Can RW principles, as compared to other terms, such as renaturing, urban green infrastructure, and biophilic design, guide the standard? Can they benefit from access, as the two suggested categories help? Can improved ideas of access at different functional levels optimise urban planning outcomes?

Urban planning for each proximate population can then address specific needs from access to UGS, air pollution and purification, cooling or temperature regulation, therapeutic benefits, sensescapes, environment for physical activity, and aesthetics, alongside the likelihood of use.

3.6. Refined Wilding

RW can provide further and improved justifications for UGS design beyond vegetative densities. It can provide conceptual guidance for any UGS type and encourages a landscape-level spatial planning across UGS and transparent spaces to ensure functional connectivity of any urban biodiversity, and then functional connectivity with surrounding biodiversity. The UGS and transparent space connectivity give scope for aquatic and green space functions, as influential to air functions, like cooling and air purification. This functional connectivity for advanced function can also frame considerations of access, and the various factors and definitions, and the benefits of access, as a human reality. The advanced consideration is in viewing UGS, or transparent spaces, compared to using these spaces for activities, in distances, by elevation and functions of different elevations and horizontal distances. In mitigative compared to therapeutic benefit functions, the definitions of UGS are also as important as the definitions of transparent spaces, different aquatic spaces, wetlands, ponds, creeks, rivers, ocean, and different air spaces, indoor [97], outdoor, ozone, and different particulate matter in transparent spaces. These expanded considerations also encourage further care with health impacts, and less considered topics of zoonotic disease, and vector-borne disease that transparent spaces can often cause. RW therefore adds an ecological interaction and process and human realities dimension to function at the space and landscape level, and across space types, determinant to access definitions, and then to optimised functional connectivity, and spatial planning. It also encourages a wild native and nonnative PTSG selection for assemblages conducive to semi-natural green space systems that require less maintenance.

3.7. Hypothesis Proven: Mitigative Effects and Therapeutic Benefits of Access to Varying Functional Levels of Different UGS

Access to UGS as a coverage and distance minimum for sustainability and human health is the most commonly recommended and used definition of access for urban planning. The benefits of UGS are, however, various. Access to benefits can improve and specify an understanding of access, subsequently improving how access as coverage and distance from are planned according to access to benefits of different UGS. Distance of different UGS types can provision benefits for mitigative effects, and therapeutic benefits, with variables of transport, and design by different UGS types and intended use, recreational, forest park, rooftop, indoor green spaces [98] influential to benefits accessed by physically experiencing a UGS, compared to viewing, compared to being within a distance that is accessible to a mitigative effect, air purification or cooling as examples. How the different functions of each UGS result in benefits and are accessed can lead to specific measures of mitigative effects and therapeutic benefits that can inform how a suburb, compared to a city level, requires UGS coverage, and what type of UGS might be most functional for the benefits from UGS required.

The WHO [1,2,47] recommendation for a minimum of 9 m² as UGS coverage, and further measures of provision by distance are still important guidelines for urban planning. The variability in distance is influential to access to benefits, where adequately measured at local and city, and surroundings levels can inform urban planning for UGS by location, size, and type, with a consistent aim and recognition of quality in benefits provisioned. Existing terms such as renaturing and green infrastructure are, respectively, motivated by mitigative effects as urgent, and by the benefit of access categories. RW introduces an ensured functional ecological complexity of any UGS, and addresses human realities, to achieve advanced function from every UGS, and functional connectivity across every UGS and transparent space in an urban landscape. Further specificity in intended outcomes, as provisioning access to mitigative effects and therapeutic benefits is likely to be influenced by UGS selection and spatial distribution through urban planning, with UGS selection dependent on the urban development, densification, high-density city, sprawl redesign, or another horizontal urban redesign.

3.8. Implications for Urban Planning and Greenery

PTSG selections and assemblages are important for long-term outcomes, particularly trees, as they are influential to maintenance requirements and long-term sustainability of any urban tree or green space. UGS selections and experiences in planning for urban horizontal expansions are more common with variable examples of conserving and minimising impacts on the natural-environment and ensuring social and economic sustainable development. Various strategies include green belts, assessing the benefits of large parks compared to inner city urban greenery, the connective function between inner-city greenery, and replanning and implementing. For densification, the PTSG selections and assemblages maintain importance, and spatial configuration and UGS selections will be smaller and elevated.

Huang et al. [24,97] how that coverage across cities is 38.46% with a 20.27% standard deviation and a mean accessibility of 82.67% with a standard deviation of 22.89%. The equity in coverage and access is higher in higher-income countries, with lower-income countries requiring increases in coverage and access. While this trend is recognised, within a city, there are variable findings, with intra-city areas requiring more UGS or easier access for various reasons. In some cities of higher-income countries, urban heat is no longer a risk in areas of lower UGS, but air pollution is, with decreases for intra-urban suburbs and mitigative strategies required [19]. In other cases, surrounding large-sized UGS can mitigate air pollution in intra-city locations, but with a different urban landscape layout and design. These city-level factors must be considered alongside the general trend of lower-income countries requiring more UGS by coverage and access, with air pollution resulting from various factors, and urban heat experienced differently in different cities. The general climate of a country could, in some cases, welcome an urban heat increase, whereas in other cities and countries, urban heat is a significant health and morbidity risk factor, and attributable to either inequitable or just limited access and therefore limited mitigative effect of UGS. In this example, access is by mitigative effect, which might not be determined by distance, but by surrounding factors, and by private versus public access factors, including elevated greenery factors. The theory of urban planning must take into account the effect of increases in UGS and how it can decrease risk factors like urban heat and air pollution, but increase risk or push factors for lower socioeconomic groups, such as migrants [59] due to gentrification.

UGS integration requires an additional knowledge set and professional inclusion in urban planning. The additional knowledge set and profession are for design, planning, implementation and maintenance, and require individual and public space planning. Optimising UGS integration in urban planning is a localised process, with international standards and recommendations providing guidance. The planning for urban forests and even urban trees is recognised as requiring significantly informed planning to ensure long-term outcomes, by tree maintenance requirements, and minimising damage to the built environment and harm to human safety [84]. Other types of UGS require the same informed planning and design to ensure long-term and advanced function outcomes.

RW and functional urban biodiversity provide principles that can guide the definition and planning of any UGS and landscape connectivity across UGS, transparent and grey spaces, determined as appropriate for urban development that prevents sprawl. Existing measures of NDVI and density from 0 to 1 shrubs and grasses to tropical forest do not measure ecological complexity or function for UGS or urban purposes. Measures like biotope, LiDAR 3D, and fieldwork measures have improved the ability to indicate the function of ecological interactions and processes and even human realities, to address improving these functions. NDVI does, however, provide vegetative cover and density measures that can indicate carbon sequestration rates and likely ecological complexities, with additional literature and studies to confirm functions required for urban landscapes. Distance and benefits, behaviour to access that overcomes distance, mitigative effect and therapeutic benefit influential to proximate and what of a UGS is provisioned. Benefit is a degree measure of outcome by use or utility. The ESHR encourages questions about UGS type, functions and for each aspect, how variably influential distance compared to benefit, with quality and UGS type factored in. The variable or assumed social and physical benefits of UGS require factoring in for optimised UGS planning, encouraged by human realities of the ESHR. Examples from findings include that physical exercise is not reliant on UGS, but some studies indicate improved enjoyment, or incentive for outdoor time with UGS accessibility, while socialising in UGS is variably proven as improved for health outcomes, and use of closely provisioned UGS is variable by age and gender. These considerations emphasise how RW can guide access to the benefits of UGS analysis and informed planning. The anthropogenic pressures on UGS are another factor for expected service or function to the urban landscape [36,75], and built environment and human activity must also be adjusted to protect UGS quality, function and coverage.

Timely implementation to ensure the most important features or aspects of an urban development plan provides functions required for any urban landscape to mitigate harm, and to achieve proven environmental, societal and economic factors and aspects that can address and prevent the most pressing harms that urban settlements cause or experience. In this line of thought, urban planning which does not include or implement planned UGS might be able to further plan and implement with improved long-term outcomes, but in a timely manner.

Ensuring a synchronised planning and implementation that integrates UGS by adequately motivated designers as a specific example can improve the quality, function and optimised access of UGS for high-density, inner city, suburbanised, and developing, by redesign and or densification, urban areas.

4. Discussion

This article suggests that a UGS definition, and how they are planned as part of urban development, determines optimising for already understood and valued aspects of urban greenery. Reduced land take [5,6] through densifications, sprawl redesign and horizontal planning for adaptations to already used urban and built spaces to accommodate increases in urban populations [96,97,99] must include access to the necessary benefits of UGS for a quality of life. The reuse of existing spaces, for different reasons, grey and grey spaces, abandoned, planned redistributions, new cities, and newly defined city types, compact [11,12,17,47], high density [91,92], and 15 min cities [94] provide case examples. A redesign of grey and green spaces for optimised benefit is an acceptable and proven for sustainable urban development, as compared to sprawl [91,92,96,99,100]. It might also accommodate densifications as vertical expansions in built environments, which often result in decreases in UGSs. The integration of UGS in this case can factor in local landscape needs for mitigative effects, and therapeutic benefits, and surrounding UGS to optimise UGS selections and spatial configurations [4,39] for functional landscape connectivity and advanced functional urban biodiversity outcomes. For cases of densification, the redesign of grey and even grey spaces for green space and the built environment is a relevant point, with equitable development considerations for existing populations. UGS selections for densification are a specific aspect of urban planning. When responsive to benefit needed determined by local measures, UGS selections and spatial configurations can optimise sustainable urban development. Ensuring maintained UGS coverage and increases in UGS quality, by advanced function in each green space, and in urban green and transparent space landscape connectivity. This outcome from urban planning for population increases can reduce sprawl and improve how densification is a sustainable urban development. Densification more often introduces elevated UGS with different access and benefit outcomes.

4.1. UGS as a Measure of Quality of Life

Functions of air and water purification, mitigative effects, and therapeutic benefits are quality of life indicators, and ecological interactions and processes are influential to how various UGS provision functions for benefits. The mitigative and other positive functions of UGS are dependent on urban planning, for new settlements and for the redesign of existing built environments. New settlements and redesign are for various reasons and must focus on sustainable urban development, integrate aspects proven to mitigate against risk factors of climate variation and pollution, and improve the quality of life. Urban planning must therefore be accurately informed, and appropriate for the urban development and city and country, and then appropriately implemented.

The benefits of UGS are measured simply as air (transparent: light, noise, particulate), water (transparent spaces), sensescape (transparent and green space), and mitigative and then therapeutic benefits. Therapeutic benefits indicate an improvement in health, where mitigative is a preventative measure or response to reduce predicted or occurring harm. There are also the established benefits, which include a decrease in risk due to reductions in UGS coverage through urban developments, like densifications. Access and variable indicators introduce the considerations of physical access, and then distance, and then access to the positive impacts of UGS, which is influenced by the surrounding environment, location of UGS, the quality and type of UGS, and the general demographics of the population, and the socioeconomic status of the city and country, in some cases. These various benefits and UGS types are influential to access indicators, and when measured, can better inform urban plans for UGS integration, as maintaining or increasing, improved definition and understanding of UGS types can improve how urban plans effectively introduce or redesign appropriately for the urban plan. These influences can be for spatial planning and optimising functional benefits, which might include a prioritisation of benefits specific to each city and country. A consistent balance between biodiversity and human utility, by functional biodiversity and RW, can ensure appropriate choice of UGS type, and explanation of access, while satisfying the recommendations for coverage and distance, for uses and benefits. An example is the reduced distance of a UGS from a source of noise, as an improved mitigative effect [62]. Factors other than distance are the size of UGS, quality compared to quantity, utility by availability, view, use, and UGS type.

Optimising for sports, recreation and interactions with nature ensures experiences interrelated and distinct health benefits from green spaces [47,48,55]. Whereas optimising for access to mitigative factors requires different spatial planning and design, [101] for various factors, including urban heat, air pollution, water quality, pollen content, particularly combined with air pollution, then, location for mitigated effect on the natural-environment. Measures like NDVI take vegetative densities into consideration as a useful indication for carbon storage, but not for ecological functions. NDVI, density, composition and configuration measures of 0–1; however, shrubs and grasses closer to zero have an ecological complexity not measured by this index [31]. Closer to 1 tropical forest is denser in vegetation and of a higher measure, ecologically complex, but by vegetation, and by diversity. Vegetative densities indicate higher ecological complexities but not functions, which emphasises a different measure of functional biodiversity. These densities are also measured by other indicators, and some provide more specific indicators for functional biodiversity and RW [31], which can assist in informing urban planning, particularly for densification or sprawl redesign. Where measures of vegetation do not indicate significant changes in UGS by coverage of composition [40], there might be other measures that present different findings. Additional measures like biotope and Species-specific air purification index (S-API) and I-tree Urban Ecology Research Learning Alliance (UERLA) give information for ecological measures and indicators, with fieldwork measures also required. The human realities aspect of the ESHR, and for RW, encourages the more complex understandings of access, in terms of utility and benefits, influenced by functions determined by design and UGS types. Benefits include human health, physical and mental, physiological, and behavioural, to access, alongside availability. Distance and utility are seen as increasing use and benefit; however, further and availability for use can provide beneficial access.

4.2. Accessibility: Which Green Spaces Are Within Reach at Different Functional Levels?

Socioeconomic indicators and influencers on UGS distributions and access can be balanced by questions of functional levels, with the value of areas increasing with UGS increases, and subsequent development definitions of gentrification and sprawl. It is not the only push factor for sprawl, but it is an aspect of planning influential to spatial distributions and could be addressed by functional levels. UGS for urban planning must therefore ensure the prevention of sprawl and even suburbanisation without sustainable planning. This development risk leads to recommendations for UGS and greening that are, in some studies, rarely integrated into urban planning and development and are later additions. For sprawl, the integration of UGS is a consistently relevant and important integrated topic or component, where organised horizontal expansion must integrate preventative measures for conservation and protection of the natural-environment. As sprawl is an unorganised urban development, the replanning or redesigning and utilising of open green spaces, and the replanning of other UOS, or adapting the use of built spaces in sprawl, is another relevant point for UGS as part of urban planning. These planning and development strategies are expected to be quite different to an integration of UGS by provision for densification or vertical expansions to accommodate population growth in urban areas or landscapes. While planned densification in response to population growth should be different to a sprawl development, the supporting reason for including UGS in initial urban developments for population growth might require further studies. The latter response and integration of UGS to such urban developments is only proof of the benefit of UGS, distance and proximity, which is city by city, and country by country, particularly where existing urban landscapes have limited UGS, by size, type diversity, distance, and proximity. These measures must, however, take utility and use into account, and behavioural influences which can qualify distance, size, quality, type and proximity recommendations.

Urban planning for population growth and UGS can then vary by recommendation for increases across a landscape as the landscape develops, with improved access by walking, bike, or vehicle to existing UGS, and an improvement in their functional outcomes. For preventing horizontal sprawl and encouraging planning horizontal urban development, conserving and protecting natural-environment areas, and selecting conversion of already built environments, and similar strategies would be focal points. With converting already built environments to human settlements, the planning for UGS integration becomes relevant, as does ensuring UGS integration to newly built residential and settlement developments, for connectivity across the landscape as a natural-environment aspect, and then the human benefits of UGS. Studies that prove the value and need of UGS in urban centres, as compared to services, indicate that suburbanisation and suburbs, in most cases, have UGS as private residential gardens, and the need for services. For urban planning and UGS, horizontal urban population growth as a preventative to sprawl can easily provide a natural-environment connectivity function, with residential gardens. Densification as an urban development strategy to prevent sprawl does not occur easily without planning, and studies that prove human utility by health benefits, and maybe the natural-environment and connectivity functions. Urban planning for densification requires design and planning for the existing built environment, and working with different spaces for greening and different urban green types. It can be dependent on measures and reasons for the UGS value in built-up urban areas. A significant opportunity in urban development, as compared to sprawl, to address an improvement in natural-environment outcomes is the redesign and planning of already sprawled urban populations. The size, quality and distance of the park can provide mitigative effects for urban populations that are further than recommended distances.

4.3. Summative Discussion

This summative discussion presents Table 9: a summary of urban planning for different development types and functional urban biodiversity to optimise access to specific and needed benefits of UGS for sustainable urban development.

Table 9. Functional urban biodiversity for different urban developments: urban greening strategies for equitable access.

Access	Urban Development	Urban Greening Strategy	Functional Urban Biodiversity
○ Access as a matter of provisioned benefit of different functionally biodiverse UGS, specifically mitigative effects and therapeutic benefits accessed by any person or population distanced or close by. ○ The need for access varies by urban development, and area, use compared to viewing, access to specific functions of different UGS. ○ Measure functions of mitigative effect, compared to or as well as therapeutic benefits for need and respond with UGS selection, design, and spatial configurations. ○ Ensuring optimised spatial configurations for functional connectivity across a landscape of UGS and transparent and grey spaces, and according to human need and value. ○ Refined wilding for functional urban biodiversity can ensure specific functions that provision benefits for access are always provisioned, with variance in spatial configurations. ○ Blue-green spaces for cooling and other therapeutic benefits	Sprawl	Redesign with UGS integrated or reverted to UGS. Measure of access to UGS as benefits, mitigative effects and therapeutic benefits accessed, and provisioned. Then, need for specific benefits from access as a matter of functions provisioned by each UGS for the urban population and for the natural-environment.	Urban plan, design and implementation to integrate wild refined UGS for functional urban biodiversity of varying ecological complexities. Advanced function of each UGS is dependent on the UGS type selected, functional spatial configurations ensuring landscape level functional biodiversity.
	Suburbanisation	Redesign, densification and increases in service centres, with integrated UGS. Improved quality of UGS, by UGS system, or landscape connectivity. Measuring: Access to benefits of different UGS. Need for benefits from access by suburbanised area. Connectivity of greenery between suburbanised area and inner city. Planning, designing and implementing according to such findings.	Improvement in residential gardens and how they functionally connect, using refined wilding. Improvement in blue-green spaces for cooling and other therapeutic benefits Improvement in public UGS using refined wilding. Ensuring functional landscape connectivity across all suburban green spaces, and functional connectivity with inner city green spaces. The suburbanised green landscape will be functionally biodiverse according to the ESHR.
	High-density	Increases in urban greenery using micro space, pocket parks, green corridors, and elevated green spaces. Measures of specific benefits from access needed for different inner-city high-density areas. Identify UGS types that can provision specific benefits, by distance or proximity. Ensure elevated green spaces and green corridors are consistently encouraged for layout. UGS integration results from synchronised urban planning, and ongoing implementation. Look to redesign grey spaces and to integrate UGS to increase or optimise green coverage.	Functionally biodiverse greenery across high density area, with coverage prioritised but focuses to specific benefits needed, and to purified transparent spaces. Each UGS type, elevated, corridor, micro space or pocket park is of advanced function through refined wilding, with wild PTSG selections, and assemblages and UGS type selections and configuration informed by access to resources, adequate Human Resources for design, and maintenance. Wild refined UGS should require less maintenance. Redesign and optimised use of grey spaces and spontaneous or informal green spaces. Introduction and reserve of wetlands and blue spaces.
	Urban centres and cities needing to accommodate increases in urban population	Vertical expansions in built environment, with elevated greenery, and pocket parks, conserved urban greenery where possible. Implementation can be over time, with revised plans for UGS better informed by use and evaluation of developed urban areas that are implemented urban plans for sustainability, including need for specific function by UGS type.	Functional urban biodiversity guides urban planning for densification and can be integrated to build environment plans that integrate UGS. Refined wilding can inform UGS selections, spatial configurations, PTSG selections and assemblages and is motivated by advanced function.

4.3.1. Refined Wilding as Conceptual Guidance for Urban Green Planning

RW is suggested as a conceptual guidance for UGS integration to urban planning, particularly for urban developments that address population increases or for densely populated urban landscapes. The concept can ensure an advanced function from various UGS types and spatial configurations that suit densification and redesign of vertical and horizontal expansions. It can guide evaluation and response to mitigative effects and therapeutic benefits needed from access to UGS. The evaluation can occur after urban plans are implemented, to ensure that the maintenance or increased greenery is achieved from urban developments for population increases. RW also guides design and ensures responsive planning for human realities that use functional ecological interactions and processes of varying complexities, dependent on the UGS type and the landscape. The landscape level considerations are for functional connectivity between and across all UGS types and transparent spaces. It can influence and lead to the redesign of grey and green spaces, and of unsustainable developments like sprawl. The RW concept works toward functional biodiversity with two aspects of functional consistently considered and analysed, human realities and ecological interactions and processes at a system and landscape level, that human interactions with the natural-environment must be sensitive to. RW of any UGS therefore looks for and finds balance between human realities of an urban area and landscape, and a functional configuration and composition for ecological interactions and processes of varying complexities. These complexities are dependent on the type of UGS, the landscape spatial configurations of any UGS and their functional connectivity. For this reason, the definition of UGS and specific types of UGS for different urban planning and developments are important to clearly consider and plan for. The planning can be for conserving, introducing or redesigning. The redesign can be for existing UGS or for other UOSs. Where an undesigned natural-environment must undergo urban development, it must be after considering any already developed urban area for reuse, and include urban landscape, or spatial planning that conserves and minimises negative environmental impacts, and aims to achieve maximum benefit from access to maintained or functional and optimised increases in urban biodiversity organised in different UGS types. The UGS types are positively and functionally connected with all other UGS, and then with other UOS, particularly with transparent spaces across a landscape. The benefits must then be measured to optimise outcomes from urban planning that integrates UGS.

4.3.2. Functional Urban Biodiversity for Urban Planning: A Standard

Functional urban biodiversity as a standard for UGS in densification urban plans can ensure elevated and pedestrian-level design and distribution of urban greenery that is accessible. Accessibility is a benefit of the UGS, including physical and viewing access, alongside the measures of mitigative effects and therapeutic benefits. Ensuring access to UGS by coverage, quantity, minimum distance to human populations, and quality, by utility and biodiversity is a supported urban development strategy. The ESHR is more specific with ecological interactions and process function, functional complexity by vegetative densities, and stratifications, at the space and landscape levels. Some important aspects that RW ensures for urban planning for UGS include the following:

○

The importance of PTSG selections as wild assemblage choices.

○

Non-allergenic to decrease the negative effects of access to any UGS type, with varying factors of elevation and combinations with air pollution factored in.

○

Designs that encourage balance between utility and biodiversity. Optimised spatial planning for multidimensional understandings of access and benefit, advanced function, and functional connectivity.

○

An example of RW guidance for urban planning [31] is in optimising UGS types, PTSG selections, and coverage, taking significant factors like allergenic pollen and human health degradation into consideration.

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Air pollutants are proven to decrease because of UGS; however, comparisons between UGS types prove differences in allergenic symptoms in those exposed by access, use or allergenic pollen travelling in the air.

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UGS types that are more likely to be used and accessed with indirect benefits of air purification, cooling, views, and recreational uses that encourage different uses.

○

Rooftop UGS proved higher allergenic symptoms compared to a park [31], and should take selections and assemblages by each UGS type into careful consideration.

The use of RW for functional urban biodiversity by urban designers, planners, regulators and other stakeholders and professions could provide consistency and increase the quality of urban greenery implemented with urban plans for population increases particularly where external regulations require advanced function in urban biodiversity and where local populations value biodiversity and urban greenery, and where the interdisciplinarity of knowledge sets required, including forestry and ecology, are adequately resourced. The important aspects of RW can specify UGS integration to urban planning for advanced functions. Optimisation is by spatial planning and combinations by benefit of different UGS functions, and access, balance between biodiversity and human use by experience in a UGS, and ensuring a high quality of UGS by ESHR and RW standards and principles, with a focus on improved human health, improved protection of the natural-environment and improved ecological interactions and processes which can indirectly improve social and economic outcomes.

4.3.3. Refined Wilding Standard for Densification

Refined wilding is a concept compared to renaturing, novel urban ecosystems, green infrastructure, and biophilic design. All terms have alignment and complementarity with refined wilding, as refined wilding works toward a functional urban biodiversity for each UGS and across all UGS and UOS through functional connectivity. UGS are proven to be lost during densification, and when planned for, are sometimes not implemented. There are recommendations for UGS standards in urban densification strategies [7,13] to ensure implementation of UGS with urban plans, and studies that prove UGS decreases through densification. While urban planning could theoretically accept ongoing implementation and even revised plans for UGS based on the use of new urban developments, the recommendation does suggest that synchronised implementation is important. As densification is proven to decrease UGS, synchronised implementation can ensure maintained UGS coverage, or even increases, as are needed for sustainable urban development and quality of life.

RW could provide standards for any planned or implemented UGS which require monitoring and measurement over the long term. It can further define functions sought for any UGS and landscape configuration of urban greenery by functional connectivity, which requires defining for these standards, as recommendations for access mainly focused on distance and coverage by hectares or metres [1,2]. These measures are taken with GIS and other machine learning technologies, and determine accessibility, spatial distributions, and landscape configuration, and vegetative densities. Landscape connectivity can then measure how residential and public UGS functionally connect with RW and functional biodiversity, guiding the measure. It is the ESHR and human realities which could better inform urban planning and realistically plan for the implementation of UGS. It is more likely to identify and address factors that prevent synchronised implementation, including accurately informed planning regarding the importance of UGS for SDGs, and quality of life.

Examples of existing recommendations for UGS standards for urban planning consider proximity and benefits in health terms [102], with simple distance and then distance from the proportion of population, and provisioning UGS [54]. Rubaszek et al. [54] suggest as a three-category public green space system, with distance and size of a UGS determining the category. Public green space is the indicator of accessibility, as compared to residential or private green spaces which introduces definitions of access, mitigative effects and therapeutic benefits to the public green space measure. Measures of view as green view index, and mitigative effects further how access can be standardised, or how public for public green space is defined, supporting the further defining of UGS access.

4.3.4. Summary

Urban planning must conserve and reserve UGS, and to mitigate health risks, ensure transparent spaces are included, clean air and water for cooling. The UGS types for particular urban developments like densification by vertical expansion of built environment, urban sprawl redesign and horizontal expansions are variably suitable, and conservation compared to redesign, compared to relocation, compared to urban spatial layout and planning factors must be adapted to the specific city level, and designed and planned for realistic implementation. Sustainable densification, vertical expansions, and organised horizontal expansions work to overcome the proven negative impacts of sprawl resulting from population growth. Sprawl is often the result of rapid urbanisation [10,15,37] and unplanned horizontal expansions. Suburbanisation, as planned horizontal development, which can consistently include UGS as private residential gardens and public UGS in suburbanised areas, leads to reliance on vehicles for services and air pollution, as sprawl does. Residential gardens and public green spaces can be improved with UGS integrated urban planning. The option of smaller-scale and micro green spaces for densification could be better integrated, and implementation strategies for private green spaces might also increase the implementation of urban area sustainability plans. These strategies can take elevation, size, functions (mitigative, therapeutic, aesthetic), quality, and quantity into account for the specific city and population for intended positive functions and outcomes. The need to redesign or revisit urban plans to ensure implementation can be understood in urban development theory is seen benefit for different populations in urban areas and across urban landscape. The various indicators of measure and function of UGS for different urban developments to ensure sustainable urban development have led to recommendations for more scientific urban plans, optimised spatial planning, and local urban level plans to appropriately address access, use and benefit for different populations in and urban landscape. The definition and measure of UGS access can also require involution past public green space, to plan and implement UGS for specific need and provision of different measures of access, mitigative or therapeutic. Involution of access to UGS can give further support for conceptual measures that reach measure of, and guide toward advanced UGS functions that provision specific and needed benefits of access for block, city centre, and urban landscape level, and connected urban landscapes and surroundings level. The example of view compared to use, and cooling compared to air purification as a need at block by block or city by city level, begins the differentiating and specifying that can improve reason for UGS integration, and can inform selection and location of UGS type.

4.4. Recommendations

The recommendations for improved urban planning to accommodate densification, redesign and prevention of sprawl must integrate increases instead of losses of UGS in planning and implementation. Losses of UGS during densification and losses of natural-environment during horizontal expansions are considered significant and a challenge.

As part of a recommendation for standards, access and measures of access, and the definitions of UGS and conceptual guidance for expectations could further improve planning and implementation.

Spatial distribution, including an optimising of UOS, UGS selections, and landscape connectivity are part of an integration of UGS into all urban planning, particularly for densification and urban sprawl redesign. It could also plan for realistic implementations according to human realities. RW guidance for a measure and standard would ensure a sensitivity to functional ecological interactions and processes, and human realities of any UGS type, and functional connectivity across and between all UGS types, and grey and transparent spaces. Gray spaces give reason for analysis, redesign and equity assessments, Specific recommendations from findings include (i) finding a balance in UGS increases, and improved access; (ii) optimising access to the benefits of UGS as a matter of specific functions of different UGS; and (iii) optimising spatial configurations of UGS. This is with the view of urban planning for UGS integration informed by recommendations and with guidance from refined wilding for functional urban biodiversity.

4.4.1. Finding Balance Between Social Sustainability and UGS Access

Finding a balance between mitigative effects and therapeutic benefits requires accurate measures of access to and from UGS, and risk factors of decreases and increases in UGS for urban planning. Gentrification, maintenance, and risk factors like safety, crime, falling branches, discrimination, and allergenic pollen emissions are all risk factors for consideration when recommending increases in UGS.

Ensuring UGS quality, selection, and need for access to benefits is essential for UGS integration into urban planning to obtain sustainability goals.

Accurate measures of benefits from access, like cooling and air purification inform accurate locating for specific access to benefit needed. Surrounding UGS and their benefits compared to smaller or mid-sized inner city urban greenery, are influential measures of access for inner city residents.

Different urban developments require different UGS selections, functions and spatial configurations, including elevated, pedestrian level, mitigative, functional landscape connectivity, recreational use, visual and aesthetic benefit, with coverage for cooling or air purification effect.

Urban Planning Must Therefore

Enter more advanced, interdisciplinary and multi-functional considerations when integrating UGSs, particularly as aspects of access. Access measures of two categories of benefit, and functions that provide the benefits vary with distance.

For UGS inclusion and implementation—evaluate and assess a landscape accurately for existing access to benefits, and need for each benefit at block, suburban, city and landscape levels while ensuring adequate planning response by UGS selections and spatial configurations that ensure provision by function and then access to specifically needed benefits.

4.4.2. Optimise Access to Benefits of UGS Using Urban Planning

In most cases, access by recommendation is a measure of physical distance and coverage of UGS [1,2,47,54], with implementation not just urban planning for UGS a significant limitation. Urban densifications lead to decreases in UGS, not just limited increases. For some of the studies found, access is about utility, and frequency and duration of use by different demographics, age and gender are examples, influenced by availability and quality. Access can also be about the functional role that any UGS plays, from views and visual, or other sensory access, sounds, scents, air purification and heat mitigation by distance, metres from location, horizontal or elevated, to physical use and interaction with a UGS. The limited urban cooling of elevated greenery for pedestrian level is an example of measures that are variable by location, 3D and not just for coverage. The variable need for UGS for urban cooling compared to air purification to reduce air pollution is also a more advanced consideration of function by access, and the type or definition of access. Measures of appreciation, and perceived or real risk factors which influence access, such as wild animals, pets, falling branches, zoonotic disease, vector borne disease, safety at night or during the day for children, elderly, and adults are influential to use of UGS while coverage can have an access by functional effect, without being within the recommended distance that would qualify as access by particular measures.

Densification might more appropriately consider micro green spaces and pocket parks, alongside elevated green spaces, indoor and outdoor, squares, wetlands, walls, and rooftops.

Urban planning, particularly for densification, might improve with standards that specify scenarios or options for different UGS types, and their advanced meanings of access and benefit.

For horizontal developments, a focus on redesign and no land take strategies, and already proven benefits of green belts, landscape connectivity across all UGS types.

Densification might also benefit from redesign, particularly for grey and gray spaces, and for some green spaces.

4.4.3. Optimise Spatial Configuration and Selection of UGS Types

Existing studies and recommendations for distances, and types of use and benefits for proximity, and access definitions, and or as compared to physical use of a UGS are required considerations to optimise spatial configuration, including UGS type selection, quantities, quality and functional connectivity across urban open spaces (UOS). This optimisation relies on various measures and indicators at the local level, and further measures of health and environmental benefits dependent on quality, type and function, design and distance, for therapeutic and recreation, and health as compared to regulation of daily natural-environment, and environment, and mitigative effects to address specific challenges. The variable use of UGS, where provisioned by distance [54] and even multi-functional design, introduces the importance of considering the mitigative effect [102,103] and other therapeutic benefits, alongside the physical use of a proximate UGS. View of a UGS is a selected example; the variable therapeutic benefit of viewing a UGS compared to physical access and use of a UGS can then be compared to the mitigative effects of different UGS. Elevated UGS have different mitigative effects at the pedestrian level, by UGS type, vegetative cover, and PTSG selections and assemblages. The effects of cooling and air contamination compared to purification are an example, influenced by existing air pollution levels combined with allergenic emissions, and then air purification functions of nearby and close UGS of different types, and elevations. Another example is how urban greenery can shape local activity patterns. UGS measured from a single dimension might not reliably predict engagement in health-related activities across age groups [57], reinforcing the need for balanced and context-sensitive UGS measures and design to support inclusive public health.

Monitoring of urban landscapes to inform planning must assist in determining functional biodiversity at a landscape level as intended, influenced by and to inform spatial, and UGS type selections, and quality optimisation.

The benefits of access to different UGS can better inform this spatial planning of UGS and selection of UGS type, while ensuring a functional connectivity and optimised use of UOS across an urban landscape.

5. Conclusions

Urban greening is often presented as a matter of environmental and human justice [18,89]. The response to this issue must be accurate to achieve what is effectively sought. A focus on access without specifics of benefit can lead to generalized UGS integration. Refined wilding can provide conceptual guidance for UGS integrated urban planning, and even a standard for UGS integration for densification, urban sprawl redesign and other horizontal urban developments that accommodate population increases. The access to UGS as a focus for recommendations can further the conceptual guidance for advanced function. Mitigative effects and therapeutic benefits of UGS are two categories for benefits from access to UGS, which have several subcategories. They are provisioned benefits. Some are reliant on proximate exposure, viewing or physical use as examples, or other exposure measures, whereas other benefits are experienced and accessed due to distanced functions. The benefits of access are directly influenced by the ESHR concept, which is functional ecological interactions and processes at varying complexities, functional connectivity between all UGS across an urban landscape, and human realities. The concept encourages a sensitivity of human interactions with the natural-environment. The UGS type is influential to and can be influenced by PTSG selections and assemblages. The RW concept for functional urban biodiversity provides principles and interdisciplinary guidance and goals for UGS selections, design and configurations. Wild PTSG selections and assemblages, and location determine optimised spatial configurations for functional landscape level urban biodiversity. RW of any UGS looks for and finds balance between human realities of an urban area or landscape, and functional configurations and compositions of PTSGs and various ecological interactions and processes. The complexities of biodiversity are dependent on the type of UGS, PTSG selections and assemblages and the landscape spatial configurations which ensure functional connectivity. For this reason, the definition of UGS and specific types of UGS for different urban planning and developments are important to clearly consider and plan for. The planning can be for conserving, introducing, or redesigning. The redesign can be for existing UGS or for other UOS. Where an undesigned natural-environment must undergo urban development, it must be after considering any already developed urban area for reuse, and include urban landscape, or spatial planning that conserves and minimises negative environmental impacts.

Recommendations include improving policy for UGS integrated urban planning and improving uptake of policy by urban planning [8,9,10]. Comprehensive assessments of UGS inequality and inequity in cities worldwide are lacking [6] and can better inform how urban planning can respond to and achieve sustainable urban development. Venter [19] provides further consideration for inequity studies by access and benefit, comparing cooling and air pollution by distance and coverage of UGS for lower socioeconomic areas and populated areas of a city. This study supports a need to respond to international studies of equity and access of UGS at an intra city and country level to reach consideration of mitigative effects and therapeutic benefits, which are variably influenced by distance, UGS type and spatial configuration. It also works to consider urban planning theory that can encourage implementation over time, and synchronised planning and implementation.

Urban plans and their implementation might require adaptability over time, and an opportunity for revising unimplemented aspects of a plan before implementing. They can improve in plan content, with multi-line cross-sectoral synchronised approaches to sustainability for urban development. More specific guidance leading to synchronised improvements in each sector and planning stage could improve UGS integrated urban planning and implementation. The two categories of benefits from access to UGS require different strategies for UGS integration into urban planning. As a mitigative effect, air pollution requires a different spatial configuration compared to cooling [19]. Specific studies look at optimising spatial configurations for various definitions of access and consider use and utility. Studies have provided guidance to urban planners for decades. There is still a need to identify greening principles and to develop urban development policies for a better urban quality of life. This need for implemented greening principles for policy to influence urban planning is particularly relevant for high-density cities, densification plans, sprawl redesign, and improvements for suburbanisation.

5.1. Strategies

Strategies can address the need for specific benefits in each city area and urban landscape. For urban heat [100,102,103,104,105] these strategies are proven to require land use type specification. Impermeable surfaces, passive-built environment design, and then vegetative cover by quality and square metres are most effective but variably needed by these different urban land use types or zones [103]. Venter et al. [19] prove how air pollution mitigation requires different UGS coverage and access compared to urban heat. This difference is significant support for city-specific urban planning for UGS integration as a strategy and is only for two of the mitigative effects that UGS and urban planning can achieve. Extreme weather, natural disasters, industrial activity, and reliance on vehicles also require mitigative effects from UGS and sustainable building.

Urban planning that prevents conversion of the natural-environment through redesign of existing urban settlements, and ensures a sustainable built environment, buildings and public built spaces, is most preventative and a basis for strategies. As UGS is significant for sustainable development, horizontal urban growth can provide significant opportunity for improving advanced function and connectivity across a suburban or urbanised landscape. The preventative urban plan of densification also requires the same basis for sustainable building strategies and integration of UGS for benefits, and connectivity with surrounding UGS, as redesign of active or abandoned urban settlements of sprawl or suburbanisation.

A well-regarded urban planning strategy for UGS is high coverage to lower distances for access, pedestrian [53,54] and elevated levels, and encouraging an effective use of UGS and water bodies [9] for cooling and temperature regulation as an example. With the findings of mitigative effects and therapeutic benefits taken into consideration, strategies are presented for (i) functional urban biodiversity and (ii) urban planning that optimises access to the benefits of UGS.

5.1.1. Functional Urban Biodiversity Strategies

• Ensure functional urban biodiversity of advanced function for every UGS, and for landscape-level connectivity, appropriate planning and implementation for each city and country.
• Ensure the UGS design balances human activity and biodiversity.
• Ensure individual-level UGS integration to dense urban developments and to high-density cities.
• Ensure functional green and transparent corridor connectivity across high-density urban centres to connect surrounding natural areas and environments.
• Work with clear definitions of UGS and the various types of UGS and ensure high quality and advanced function of all UGS at the space and landscape level connectivity, and across urban open spaces, specifically, transparent spaces.
• Ensure transparent and green spaces are introduced and conserved or reserved to address the required benefits of UGS mitigative effects and therapeutic benefits.
• Ensure functional connectivity across UGS, transparent spaces, and integration to the built environment and other grey spaces.
• Ensure adequate importance is given to PTSG selections, and wild selections and assemblages for any UGS, with priority to non-allergenic, functional assemblages, and functional assemblages that do not always require dense vegetation, but wild semi-natural systems that self-maintain.
• Work from measures of NDVI, S-API and UERLA as starting points for PTSG selections for air quality and densities that can inform ecological interactions and processes and ptsg selections.
• Ensure functional design for microclimates and measures for the cooling effect that can efficiently and strategically allocate locations for UGS according to desired and required mitigative effect.
• Provisioning and proximity of functional biodiversity as a measure of access requires further measures of quality, utility, and appropriate planning for urban development.
• Redesign of grey spaces, abandoned and informal can provide an opportunity for advanced functional urban biodiversity and functionally connected transparent spaces (aquatic and air) that provide functions for human populations and the natural-environment.

5.1.2. Urban Planning Strategies to Optimise Access to the Benefits of UGS

• Spatial inequality in access to UGS between 1990 to 2020 varies by regions, with different development strategies to address this variation evident.
• Planning to reserve blue and green spaces and include wetlands and other aquatic spaces.
• Reaching the minimum square metres per capita for UGS.
• Redesigning sprawl and suburbanised areas for sustainable use and population increases.
• Vertically develop, or increase density as layout planning, with UGS included.
• Ensure an optimised quality in UGS selection and spatial distribution to ensure optimised access by mitigative and therapeutic function.
• Take the delayed implementation of urban planning for UGS as an opportunity to revise and improve according to any human use of new urban developments.
• Convert abandoned, underdeveloped green spaces, and grey spaces to advanced function UGS, and functionally integrated sustainable spaces with UGS where access to identified benefits is needed.
• Ensure an accurate measure and recommendation, plan and monitoring of access to UGS by using mitigative effects, and therapeutic benefits, as well as physical access for interaction compared to viewing access.
• Ensure urban planning for UGS integration responds to urban development trends, local conditions and mitigative effect and therapeutic needs, utility trends, and use compared to access and availability.
• Spatial optimisation for urban planning can consider quality and quantity measures of access compared to geographic location and distance.
• Socialising and physical activity in UGS are commonly believed to improve therapeutic effects; however, several studies variably prove any significant correlation. The proven benefits and use of UGS can assist in determining parameters for access that inform urban planning and selection of UGS type for intended benefits by type of access.
• Consider the benefits of access to UGS by provision or availability as indicators influenced by both distant and proximate, and simple, close-distance UGS of various types.
• Consider standardising the benefits of UGS by type and adapt by local requirements.
• Densification that achieves required increases or maintains UGS, as micro green spaces, rooftop and wall greenery, edges and ecotone, pocket parks and gardens also achieves functional connectivity with surrounding UGS and across UOS. In some cases, mid-sized parks and urban greenery of mid to large size are elevated or at the pedestrian level, functional connectivity also achieves 3D and 4D outcomes.
• Focus RW and benefits of UGS access to gray spaces.

5.2. Future Research

Duan et al. [36] and Li et al. [91,92] in studies for high-density cities recommend that future research focus on the distribution and evolution of smaller UGS. It is also recommended that higher-resolution remote sensing data (10 m or higher) be employed to monitor UGS fragmentation with greater precision, and green view complement remote sensing. Future studies could.

Benefit from the application of quantitative methods to better elucidate the key driving factors of UGS change, and might also.

Better quantify and determine advanced functional connectivity across a densely populated and built-up urban landscape.

Further specify how different UGS address the functional needs of different population types, and different functional needs of different cities and countries, can provide a reason for integrating UGS into all urban planning. Each urban landscape requires specific functions from each UGS.

Give local findings to ensure an accurate response by urban planning for equitable access to UGS. Findings of lower socioeconomic status and lower UGS by square metres are variable by city and country, with general findings of lower-income countries having inequitable access.

Develop or further verify integrated frameworks that ensure well-implemented UGS for any urban development, including frameworks that accommodate different urban planning theories [106], such as adapted plans for late implementation.

Ensure and give accurate measures for the recommended categories of benefits from access using combined methods and technologies. The measures, and software, and technologies used to measure UGS location, spatial configurations and even quality by vegetative density and composition are significant factors for future research.

Response to these measures need to accurately satisfy gaps in optimisation of advanced function of UGS across an urban landscape and can be guided by refined wilding and the functional biodiversity theory. Response guided by refined wilding for urban planning is for future research as well.

Drivers for urban planning and improved UGS quality can be informed by this research to address in-depth considerations required for sustainable urban planning and implementation [54], to address recommendations from various city types, and national plans [69,72].