Urban Afforestation as Spatial Strategy: Applied Design Research on the Eastern Greenway in Rome

Abstract

Urban forestation has become a key policy tool for addressing contemporary environmental, climatic, and social challenges. In Italy—particularly in Rome—recent climate mitigation and environmental improvement initiatives have promoted afforestation through predominantly quantitative approaches. Yet, increasing tree numbers alone is insufficient to enhance urban environmental quality or create more livable and resilient cities. An effective strategy requires a spatial and cultural vision that integrates vegetation with urban form and everyday collective life. This paper frames urban afforestation as a strategic instrument of territorial transformation, landscape design, and social regeneration. It critically examines afforestation policies implemented in Rome and the Lazio Region and compares them with international experiences in Medellín, Philadelphia, and Milan. The study highlights current program weaknesses and emphasizes the need for integrated planning and design frameworks capable of generating qualitative improvements in urban space alongside quantitative gains. The Serenissima Park case study illustrates how afforestation can function as a “green infrastructure architecture,” connecting ecological systems, urban fabrics, and communities, and supporting climate adaptation, sustainable mobility, and social inclusion.

1. Introduction

Over recent decades, the climate crisis, biodiversity loss, and widening environmental inequalities have prompted cities to reconsider the relationship between built space and natural systems. Urban afforestation has emerged as one of the most visible and widespread policy responses: planting trees has come to represent both a symbolic and a practical measure to mitigate global warming, reduce air pollution, and improve the quality of urban life. However, behind this seemingly simple action—which provides ecosystem services and helps reduce CO₂ emissions—lies a broader question concerning the form, governance, and cultural meaning of urban and landscape design.

In many European and Italian contexts, afforestation programs continue to focus primarily on quantitative indicators–such as the number of trees planted or the tons of CO₂ sequestered -while overlooking the spatial, social, and experiential dimensions that determine the actual quality of urban green space. This paper adopts a different perspective, framing afforestation not only as an environmental practice but as a design tool for constructing urban landscapes. In this sense, afforestation can operate as a territorial instrument that integrates ecological and infrastructural needs while generating new public spaces, slow-mobility routes, and biodiversity networks.

As a research unit at Sapienza University of Rome, we have contributed to developing this topic by analyzing policies implemented in Rome and the Lazio Region as part of a broader national investigation. The study reports the quantitative, spatial, and qualitative dimensions of the interventions, describing the conditions and trends that characterize their implementation.

On this basis, our work concentrates on an urban area in Rome’s eastern quadrant, where current conditions make it possible to investigate the formation of a continuous ecological corridor. The case study of Serenissima Park is examined as a potential laboratory for an ecological greenway capable of enhancing archaeological heritage and sustainable mobility, reconnecting the city with the Tiburtine landscape. Furthermore, through the analysis of three exemplary international projects–selected for their balanced integration of measurable performance, social impact, and spatial quality–the study assesses the extent to which such models can be adapted to the Roman context and to Serenissima Park in particular.

Through a “research by design” approach, a proposal was developed for Serenissima Park that integrates afforestation strategies with broader landscape interventions aimed at valorizing the area’s existing ecological and cultural assets, including a significant wetland, self-managed community gardens, archaeological remains, historic buildings, railway stations, and implementing cycling routes.

Understood in this way, urban afforestation becomes an opportunity to rethink metropolitan form and to reshape relationships between nature, infrastructure, and public space. How can research by design inform replicable models of urban afforestation capable of linking ecological performance with spatial continuity and everyday public life, using the Serenissima Park in Rome as a testing ground?

2. Background and Theoretical Framework

The term urban forestry emerged in the second half of the twentieth century to describe a new way of understanding vegetation in cities. Coined by Erik Jorgensen [1] at the University of Toronto in the 1960s—when street trees were largely treated as isolated decorative elements—urban forestry reframed the city as a complex arboreal ecosystem in which vegetation is integral to urban structure and social life. During the 1970s and 1980s, research and policies highlighted the environmental and health benefits of urban greenery, including improved air quality, reduction in urban heat islands, noise attenuation, psychological well-being, and biodiversity enhancement [2,3,4]. This work helped establish an interdisciplinary field connecting ecology, spatial planning, landscape architecture, health studies, and the social sciences [5,6]. From the 1990s onward, urban afforestation entered mainstream international sustainability agendas.

In the early 2000s, the FAO’s Urban and Peri-urban Forestry (UPF) program provided guidance for incorporating vegetation into planning strategies [7]. At the same time, the UN’s World Urban Forum and the New Urban Agenda [8] recognized afforestation as part of broader Nature-Based Solutions (NBS), which combine climate mitigation with spatial and social improvements in cities [9].

In Europe, the European Green Deal and the EU Biodiversity Strategy set ambitious goals, including the planting of three billion trees by 2030 and the development of Urban Nature Plans in cities with more than 20,000 inhabitants [10,11]. These policies promote urban ecological networks—such as linear parks, green corridors, and nature-based drainage systems—capable of improving climate resilience and public health.

Comparable efforts have emerged globally. In the United States, the Urban and Community Forestry Program [12] has developed management models based on planning, participation, and monitoring. In China, the National Forest City Program established large-scale metropolitan “green belts” [13,14].

In Italy, interest in urban afforestation has increased in recent years. The Climate Decree [15] and funding through the National Recovery and Resilience Plan require metropolitan cities to adopt urban and peri-urban forestry plans. The aim is to reduce pollution, adapt cities to climate change, and expand urban green areas. Notable initiatives include Forestami in Milan (target: three million new trees by 2030) [16], the Green and Biodiversity Plan in Bologna [17], the Ossigeno program in Lazio [18], and afforestation strategies promoted by the Metropolitan City of Rome [19].

According to FAO estimates, more than 55% of the global population currently lives in urban areas, a figure expected to rise to 70% by 2050. For this reason, research on urban forestry increasingly goes beyond simple counts of planted trees but is crucial in determining the overall character of the landscape and urban space [7]. Current studies assess the ecosystem services generated by afforestation—carbon sequestration, thermal regulation, biodiversity enhancement—as well as social benefits such as environmental equity and stress reduction [3,20] but lack in stressing the importance of landscape design.

A central issue concerns environmental justice and access to urban green space. Numerous studies show that lower-income neighborhoods typically have fewer trees, higher pollution levels, and greater health risks. In this sense, afforestation is not only an ecological practice but also a political act aimed at ensuring collective rights and environmental equity [21].

Particularly relevant is the work of Bell et al., which investigates the role of green-space design at both regional and local scales, showing how tree composition, perception, and ecological functioning are interrelated [22]. This underscores the need for holistic, cross-disciplinary approaches.

Within this framework, contemporary research on urban afforestation generally follows three main approaches:

• Studies based on statistical and quantifiable scientific parameters. This group includes studies based on environmental metrics (such as CO₂ sequestration, surface temperature, and biodiversity levels); climatic and GIS-based modelling; quantitative indicators of tree canopy cover. It represents the dominant line of research derived from urban ecology and urban climate science [23,24,25];
• Research in the humanities and social sciences, focusing on cultural, spatial, and social dimensions. This group includes studies that examine: the perception of green spaces; environmental justice and access to urban green; the cultural meanings of landscape; everyday practices of public space. This research tradition is well established in urban geography, landscape studies, and urban sociology [26,27,28];
• Hybrid approaches that integrate quantitative analysis with spatial and design-oriented interpretation. This category is now well recognized in recent literature on: Nature-Based Solutions, Landscape Urbanism, Ecological Urbanism. These studies interweave scientific data with design processes, scenario-building, and spatial transformation strategies [29,30,31].

This paper aligns with the third perspective. Its contribution lies in critically examining current sectoral policies while advancing a multidisciplinary approach that links collected data with spatial design strategies capable of generating methodologically replicable interventions.

3. Materials and Methods

3.1. Research Context

This study was conducted within the National Biodiversity Future Center (NBFC), one of Italy’s five national research clusters funded through the National Recovery and Resilience Plan. Structured according to a Hub & Spoke model, the Center promotes collaboration between natural sciences and design disciplines with the aim of regenerating biodiversity and improving quality of life in urban and metropolitan environments.

Within this framework, the Politecnico di Milano coordinates Spoke 5 (Urban Environment and Health), which involves several Italian universities. The main objectives include mapping urban biodiversity, designing green infrastructure systems, and developing a catalog of Nature-Based Solutions adapted to Mediterranean contexts.

The Sapienza University of Rome—through the Department of Environmental Biology and the Department of Architecture and Design—contributes to research on urban biodiversity and afforestation from an integrated design perspective. The research group focuses particularly on the climatic, cultural, and morphological specificities of Central Italy, with the aim of formulating replicable models for cities characterized by significant territorial discontinuities, such as the metropolitan area of Rome.

3.2. Territorial Scope

The research initially examined urban afforestation programs implemented in the Lazio Region and in the City of Rome, in order to position the topic within ongoing policy frameworks and operational practices. The analysis highlighted predominantly quantitative approaches, focused on tree counts and sequestration targets, with limited attention to spatial quality, ecological connectivity, and social use of urban green spaces.

Subsequently, the research focused on the Metropolitan City of Rome (~1287 km²; ~3 million inhabitants), the regional core of the Lazio Region (~17,000 km²; >5.8 million inhabitants). This territory features predominantly hilly morphology (54%), extensive alluvial plains, and valuable coastal and fluvial ecosystems that structure metropolitan settlement.

Within this context, particular attention was given to the eastern sector of Rome along the Aniene Valley, selected as a representative setting to test an integrated afforestation and design approach. The Serenissima Park emerged as a key case study: located between the A24 motorway and the high-speed railway line, this urban edge condition is characterized by degraded residual spaces, infrastructural barriers, and fragmented ecological continuity. At the same time, it offers significant potential for afforestation, ecological restoration, and landscape reconnection.

3.3. Research Objectives

The research group’s objectives were to:

• Identify the main urban afforestation programs implemented in Lazio and in the metropolitan area of Rome and analyze their benefits and limitations;
• Select national and international case studies exemplifying integrated afforestation approaches;
• Identify priority areas in eastern Rome for increasing natural capital and ecological connectivity;
• Develop a “research by design” case study for the Serenissima Park, including:
  analysis of spatial potentials and criticalities;
  • Identification of areas suitable for afforestation;
  • Definition of design goals and spatial strategies;
• Assess the coherence between forestry objectives and ecological, historical, morphological, and social conditions;
• Investigate the principles for a new eastern metropolitan greenway extending from Rome to Tivoli.

3.4. Sources and Materials

The research drew upon:

• National and international literature on urban afforestation and green infrastructure;
• Institutional and regulatory frameworks (e.g., DL 111/2019; NRRP Mission 2; FAO and European Commission guidance);
• Climate, land-use, and ecological datasets from the Lazio Region, the Metropolitan City of Rome, and ISPRA;
• Quantitative data from local afforestation programs (Ossigeno, Forest for Rome, Riforestiamo Roma);
• Existing cartography, orthophotos, historical maps, and community-generated spatial documents;
• Direct field observations and photographic surveys, particularly in the Serenissima Park area.

3.5. Methodology

Methodologically, the research combines quantitative analysis, qualitative assessment, spatial interpretation, and research by design. The process is structured into four interconnected phases:

• Comparative Analysis of Afforestation Programs.

Analytical indicators derived from regional and metropolitan programs—number of trees, total area, species selection, canopy density, planting locations, soil characteristics—were compared to identify recurring implementation patterns and critical limitations, particularly the lack of integrated spatial strategies.

2.

Selection and Analysis of Exemplary Case Studies.

Three international cases—Medellín, Philadelphia, and Milan—were analyzed for their capacity to integrate spatial configuration, ecological performance, and social dynamics, offering interpretive models adaptable to the Roman context.

3.

Identification and Classification of Green Areas in Eastern Rome.

Using GIS-based analysis and open ecological datasets, potential sites for afforestation were identified, with particular attention to discontinuities and opportunities for ecological and mobility reconnection. The Greenspaces platform (Carabinieri Forestali CUFAA + MIT Boston) and the regional digital twin (active from 2025) were employed to simulate growth dynamics, land consumption, and CO₂ uptake. This analysis led to the selection of Serenissima Park as the primary project site.

4.

Design Scenarios for the Serenissima Park.

The final phase developed spatial scenarios and impact assessments aimed at enhancing ecological connectivity, sustainable mobility, and the cultural identity of the landscape. The resulting project is conceived as methodologically adaptable and potentially replicable in other metropolitan contexts with similar fragmentation dynamics.

By integrating analytical and projective processes, this methodology positions urban afforestation not solely as an environmental action but as a spatial and social design operation capable of reshaping the metropolitan landscape.

3.6. Research-by-Design Operationalization

• Inputs.

The design process was informed by the combined use of spatial datasets (land use, ecological layers, heat-island mapping), on-site surveys, policy documents, historical cartography, and photographic documentation. These materials provided the empirical basis for identifying spatial potentials, constraints, and afforestation suitability within the Serenissima Park area.

2.

Analytical tools.

GIS-based analyses supported the classification of green areas, the mapping of ecological discontinuities, and the simulation of afforestation scenarios. Landscape-interpretation tools and cross-scale diagramming were used to translate analytical findings into spatial hypotheses.

3.

Design.

The project was developed through iterative cycles—moving from preliminary spatial frameworks to alternative scenario development, to refinement of afforestation strategies in relation to ecological, mobility, and heritage constraints. Each iteration was evaluated in terms of feasibility, ecological performance, and spatial quality and coherence.

4.

Link between findings and spatial strategies.

Outputs from the analytical phases directly informed the structure of the Serenissima Park proposal, guiding the definition of planting zones, species assemblages, ecological corridors, and public-space connections. The iterative method ensured that design choices were continuously tested against climatic data, soil conditions, and territorial morphology.

4. Results

4.1. A Predominantly Quantitative View of Afforestation

The analysis of regional (Lazio) and municipal (Rome) initiatives implemented between 2019 and 2024 (

Table 1. Major green-infrastructure and afforestation programs in Lazio and Rome.

Area	Program	Timeframe	Scale	Outputs to Date	Targets	Typical Densities
Regione Lazio	Ossigeno	2019→	Regional (grants)	445+ projects; latest call ≈42,000 plants; ≈4000 tCO2/yr	6 million trees (regional)	Small sites; 10–12 trees per intervention
Roma Capitale	Forest for Rome	2022→	City (diffuse)	Micro-forests on residual land	CO2 & UHI mitigation	≈10 trees/intervention; ≈40 tCO2/yr (est.)
Roma Capitale	Riforestiamo Roma	2024–2025	City (street trees)	≈5800 trees planted in 2024	9500 by 2025	—
Roma Capitale	Managed stock (census)	2016 baseline	City	≈312,583 municipal trees; ≈4000 ha	—	≈78 trees/ha
Città Metropolitana di Roma	Metropolitan Forestry/PNRR	2024→	Metro area (incl. Rome)	≈1,000,000 plants on ≈930 ha (≈1075/ha)	New urban/peri-urban woods and corridors	—

) shows that urban afforestation has been approached primarily as a quantitative or compensatory measure—focused on tree counts and estimated CO₂ absorption—rather than as a lever for spatial and social transformation.

• The Ossigeno program delivered over 440 planting interventions (≈180 in Rome), mostly on small or marginal public plots (school grounds, minor parks, institutional parcels), with an average of 10–15 trees per site. These data indicate a prevalence of small-scale and dispersed interventions. The result is a mosaic of micro-interventions with limited structural or territorial impact [18].
• Forest for Rome (2022) introduced micro-forests to address CO₂ sequestration and urban heat-island effects; however, interventions, to date have mainly consisted of punctual plantings with no overarching ecological or spatial network vision [32].
• Riforestiamo Roma focuses mainly on tree replacement, maintenance, and renewal operations rather than territorial-scale afforestation (≈9500 trees in 2024, many linked to Jubilee-related works), this confirms the program’s emphasis on renewal and management operations rather than extensive new afforestation [33].

4.2. Fragmentation and Limited Intervention Scale

GIS analysis reveals a high degree of spatial fragmentation: most existing or newly planted patches are smaller than 1 ha and seldom connected through ecological corridors or continuous public green. The predominance of micro-interventions results in discontinuous patches of vegetation, which affects the capacity to achieve landscape continuity, climate regulation, biodiversity enhancement, and accessible public space networks.

Institutional fragmentation also contributes to this situation. Multi-level governance (Region–Metropolitan City–Municipalities), without a unified strategic framework, leads to discontinuous interventions. In Rome, the division of responsibilities across 15 Municipalities with partial green-management competencies influences coordination and long-term maintenance.

4.3. Potentials and Limits of the Regulatory Framework

The Climate Decree and the National Recovery and Resilience Plan (NRRP) provide binding targets and funding for urban and peri-urban forestry. However, operational directives remain largely generic. Project documentation typically prioritizes quantitative parameters (number of trees, surface area) over qualitative spatial, functional, or social criteria which affects the capacity of afforestation initiatives to contribute to coherent ecological networks and to the improvement of public-space conditions. Moreover, the absence of a public, integrated monitoring system affects transparency and assessment—particularly regarding planting timelines, maintenance strategies, survival rates and influences the evaluation of long-term ecological performance [34,35,36].

4.4. Summary of Results

The territorial analysis generated two complementary sets of results: empirical evidence and design-related considerations.

• Quantitatively, data from regional and municipal initiatives indicate that each intervention involves, on average, the planting of 12 trees, corresponding to an estimated annual CO₂ absorption of approximately 500 kg per site. Across the Lazio region, this results in a total of roughly 15,000 newly planted trees and about 625,000 kg of CO₂ absorbed per year.
• Spatially, GIS analysis reveals that interventions are predominantly micro-scaled and spatially isolated, with most patches below 1 ha and rarely integrated into ecological or public accessibility networks. These patterns reflect the prevailing distribution and location of planting sites selected within the current programs.

From a design perspective, the patterns emerging from these data highlight a set of critical issues:

• Most interventions appear punctual and dispersed within the regional and municipal territory;
• Quantitative parameters remain the primary criteria guiding the implementation of recent afforestation programs;
• Urban edge areas—particularly in eastern Rome—represent strategic opportunities to reconnect natural systems, residual landscapes, infrastructures, and cultural assets;
• Emerging tools such as Greenspaces and regional digital twins can enable shared, evidence-based monitoring and governance;
• Integrated approaches linking ecological, spatial, and social dimensions can support the development of more continuous green infrastructures.

5. Discussion

5.1. From Quantity to Quality: Toward a New Culture of Urban Green

While urban afforestation policies in Lazio and Rome remain largely quantitative and fragmented, several international cases demonstrate more integrated approaches that couple ecological performance with spatial and social quality. These examples suggest a growing awareness that urban afforestation cannot be conceived merely as a compensatory ecological practice.

Evidence from Italy and abroad shows that the number of trees planted does not correlate directly with territorial impact. What proves decisive is the quality of the project, meaning its capacity to interconnect vegetation with slow mobility systems, water networks, neighborhoods, and everyday public life. When conceived as a spatial device, afforestation can function as true urban infrastructure—regulating microclimates, enhancing biodiversity, and reshaping public space while supporting social inclusion and environmental well-being.

The case studies examined in this research were selected as exemplary instances in which measurable ecological outcomes, spatial design, and social impact coexist productively. Their analysis allows us to assess the extent to which such models can be adapted and transferred to complex territorial contexts such as the metropolitan area of Rome, where ecological discontinuities, infrastructural barriers, and uneven green distribution present both challenges and opportunities for integrated urban transformation.

At the same time, international experiences demonstrate that ecological corridors can generate meaningful improvements only when they overcome the logic of isolated, site-specific interventions and contribute to wider spatial transformations. Achieving these outcomes requires conditions that sustain continuity—long-term maintenance, coordinated governance, and secure funding—without which the ability of afforestation programs to enhance ecological connectivity and reshape urban environments is significantly constrained.

5.2. Medellín: Green Corridors as Climate Infrastructure

The Green Corridors Program (2016–) in Medellín represents a paradigmatic shift from fragmented greening to the construction of a continuous ecological network. The project transformed major roads, riverbanks, and public mobility axes into vegetated corridors linking hills, parks, residential neighborhoods, and metropolitan public spaces. The system currently includes more than 30 km of shaded linear routes, 70 ha of new green areas, and over 800,000 trees and shrubs and 2.5 million native plants.

The strategy was not based solely on increasing canopy cover, but on restructuring the city’s ecological and social metabolism. The corridors were designed as climate infrastructures, with three complementary objectives:

• Microclimate regulation: dense multilayered vegetation was used to reduce radiant temperature and cool exposed asphalt and concrete surfaces, producing a measured drop of approximately 2 °C in corridor areas;
• Ecological connectivity: native species and stratified planting supported pollinators and seed dispersal, improving urban biodiversity and reconnecting fragmented habitats;
• Social and mobility integration: the corridors run along bus lines, bike lanes, and pedestrian networks, leading to a 34% increase in cycling and new opportunities for public interaction in formerly inhospitable spaces.

A further strength of the project lies in its design governance: landscape architects, botanists, mobility planners, and municipal green maintenance teams collaborated under a unified project vision, coordinated directly by the city’s environmental authority. This ensured coherence in species selection, soil preparation, irrigation, and long-term management.

Importantly, the project coupled ecological goals with economic and social inclusion. The maintenance model employed local green workforce training programs, generating stable jobs and community stewardship, thereby embedding the corridors within social life rather than treating them as isolated environmental interventions.

In summary, the success of Medellín’s Green Corridors [37] derives from (Figure 1 and Figure 2):

• A network-based strategy, rather than isolated planting;
• Design integration across ecology, mobility, and public space;
• Continuous maintenance and local stewardship as structural components of the project;
• The use of vegetation as urban infrastructure, not decorative planting.

The Medellín case also highlights potential risks, especially the possibility that the spatial structure and ecological functioning of the corridors may weaken if the continuity, density, and stratification of vegetated areas are not preserved over time.

5.3. Philadelphia: Afforestation as Environmental Justice

The Philly Tree Plan (2023) was developed in response to a 6% decline in urban tree canopy between 2008 and 2018, a reduction concentrated in neighborhoods with the highest heat exposure and the lowest incomes. The plan sets a target of 30% canopy cover by 2035, prioritizing areas where climate vulnerability, air pollution, and health risks overlap.

Unlike compensatory planting strategies, the Philadelphia model explicitly links afforestation to environmental justice. Tree planting is not distributed uniformly across the city but is spatially targeted toward “heat-vulnerable” and “tree-deprived” districts, based on combined indicators of income, demographic composition, public health data, and surface temperature patterns.

A key operational actor has been the Pennsylvania Horticultural Society (PHS), which—through its Philadelphia Green program—has facilitated the transformation of over 3000 vacant lots into community-managed green spaces. Research conducted on these interventions reports measurable socio-psychological benefits, including a 41.5% reduction in depressive symptoms and increased perceptions of safety and well-being among local residents. Here, urban afforestation is understood not only as an ecological measure but as a tool for social cohesion, public health, and neighborhood empowerment [38].

The design strategy (Figure 3 and Figure 4) combines:

• Canopy restoration and expansion, with the principle of right tree, right place, selecting species adapted to microclimatic and soil conditions;
• Distributed small-scale greening, integrating trees, rain gardens, and pocket parks into sidewalks, vacant parcels, transit corridors, and schoolyards;
• Community stewardship networks, where planting and maintenance agreements are co-developed with residents, local associations, and schools;
• Incremental implementation, allowing the canopy to grow as community support strengthens and maintenance capacity stabilizes over time.

This approach frames afforestation as a shared civic infrastructure rather than a technical intervention. By aligning vegetation with neighborhood identity, public health priorities, and community-driven maintenance, Philadelphia demonstrates how urban forestry can function as a generative instrument of environmental equity and collective agency, not merely as a carbon-mitigation mechanism.

However, the Philadelphia model also underscores that community-led approaches depend on strong local engagement and institutional support; without them, stewardship networks may weaken and long-term maintenance may not be sustained.

5.4. Milan: An Integrated Governance and Design Model

Forestami (2019) is a metropolitan-scale afforestation strategy aiming to plant three million trees by 2030. The initiative is coordinated by the Politecnico di Milano in collaboration with the Metropolitan City, the Municipality of Milan, regional agencies, and a wide network of civic and private actors. Its distinctiveness lies in integrated multi-level governance and the capacity to align scientific research, public administration, and citizen engagement within a unified operational framework.

The project is underpinned by a territorial strategy rather than a collection of punctual interventions. A metropolitan “green weave” is pursued by:

• Peri-urban agricultural landscapes (Parco Agricolo Sud, Parco Nord, Groane) with urban parks and neighborhood open spaces;
• Identifying strategic ecological corridors along railway lines, former industrial sites, waterways, and infrastructural buffers;
• Prioritizing planting in areas with heat-island stress, soil degradation, or low canopy coverage.

This ensures that afforestation contributes not only to CO₂ and PM10 reduction and biodiversity enhancement but also to landscape continuity and public-space accessibility. A central element of the project is its technical-operational platform, which includes the following:

• A georeferenced mapping system of existing vegetation and available planting surfaces;
• Real-time monitoring tools that track canopy growth, survival rates, and ecosystem services;
• A public database enabling transparency and shared stewardship.

Modeling indicates that Milan’s canopy coverage could increase from approximately 16% to around 20%, marking a transition from scattered tree planting to a coherent metropolitan green infrastructure model [16].

Design plays a structural role: landscape architects and urban designers guide the spatial configuration of new green corridors, public edges, and connective open spaces. Afforestation thus becomes part of a broader project of urban regeneration, linking mobility, ecological performance, and neighborhood livability.

In summary, the strengths of Forestami (Figure 5 and Figure 6) are:

• Strategic ecological planning at metropolitan scale;
• Integrated governance and institutional coordination;
• Design-led spatial continuity rather than isolated plantations;
• Transparent monitoring and civic participation.

The Milan experience further demonstrates that metropolitan-scale afforestation relies on coordinated governance structures and long-term monitoring systems; in their absence, the capacity to maintain ecological continuity and canopy growth can be compromised.

Overall, despite differences in scale and governance, the three cases converge in showing that integrated design, monitoring capacity, and maintenance are the main determinants of long-term effectiveness.

5.5. Summary and Comparative Analysis

The case studies examined-particularly the Green Corridors in Medellìn and the greening of vacant lots in Philadelphia-demonstrate that measurable ecological benefits (such as microclimate regulation, biodiversity increase, and improved air quality) can be achieved when afforestation is conceived as spatial and social infrastructure, rather than as isolated planting. In both cases, the design of continuous, accessible, and well-maintained public landscapes has been crucial in reducing inequalities of access to green space and in fostering stronger community interaction.

In Medellìn, the creation of linear ecological corridors along mobility and river systems reorganized vegetation into continuous, layered plant communities, producing shaded public routes that are both performative (cooling, filtering, habitat-building) and socially activated (walkable, cyclable, cared for by local stewardship programs).

In Philadelphia, the transformation of vacant lots into neighborhood-managed green commons demonstrates how small-scale, distributed design interventions can improve mental health and enhance social cohesion when residents are directly involved in the design, use, and maintenance of green spaces.

In comparison, the Forestami project in Milan remains structurally anchored to quantitative canopy-expansion goals; however, recent pilot interventions and corridor-based strategies indicate a growing shift toward spatial continuity and the construction of recognizable public landscapes at the metropolitan scale (

Table 2. Comparative overview of international urban afforestation programs (Medellín, Philadelphia, Milan).

City	Program	Timeframe	Scale	Physical Outputs	Target/Goal	Measured/Estimated Benefits
Medellín (CO)	Green Corridors	2016–2019 (phase 1)	City (linear network)	30 corridors, ≈20 km, ≈65 ha, ≈8800 trees/palms	Heat-island mitigation; ecological connectivity	≈−2 °C avg. temp. reduction; PM2.5 21.81→20.26 μg/m3
Philadelphia (US)	Philly Tree Plan	2023–2053	Citywide strategy	Canopy-based (no fixed tree count)	30% canopy in every neighborhood (baseline ≈20%)	US$25.5 M/yr; ≈1000 jobs; ≈400 avoided deaths/yr; heat gaps ≈ 12 °C
Milan (IT)	Forestami	2019–2030	Metropolitan area (133 municipalities)	611,459 plants (2024); ≈1000–1200/ha new woods	3 million by 2030; +4 pp canopy	≈5 Mt CO2/yr absorption (2030 projection)

).

Taken together, these cases show that integrated afforestation strategies-combining ecological performance, spatial design, and social governance-produce multidimensional outcomes, including:

Ecological impacts: temperature reduction, CO₂ sequestration, habitat continuity, and broader adoption of sustainable mobility;

Social impacts: community stewardship networks, local job creation in green maintenance, and improvements in well-being and perceived safety.

At the same time, the cases also show that such strategies rely on specific prerequisites, including long-term maintenance commitments, stable governance arrangements, and consistent funding; without these conditions, ecological and social benefits may not be sustained over time.

Given the diversity of territorial, ecological, and urban conditions, no single model can be universally transferred. However, the comparative analysis indicates that reducing fragmentation and grounding afforestation in spatial design principles can significantly enhance its role as urban infrastructure, capable of reshaping public space and everyday experience.

This suggests a strong potential for the application of a design-led afforestation approach in Rome, especially in areas where ecological discontinuities, infrastructural barriers, and socio-spatial disparities converge.

5.6. Toward a Systemic Model for Rome

Rome possesses an exceptional quantity of green assets—more than 80,000 hectares across regional parks, agricultural areas, archaeological landscapes, and public open spaces. However, this richness does not translate into ecological continuity or widespread access. The city continues to suffer from fragmented governance, sectoral planning, and predominantly quantitative afforestation practices. A shift is therefore required from discrete interventions to systemic, design-led strategies capable of shaping territorial structure and everyday spatial experience. At the same time, international evidence shows that such a transition requires specific prerequisites, including stable governance coordination, long-term maintenance commitments, and adequate funding mechanisms to ensure continuity and ecological performance.

This transition can be articulated through four complementary principles:

• Ecological Connectivity

Linking existing green fragments across the urban–peri-urban gradient to form continuous habitat networks and climate-cooling corridors.

2.

Infrastructural Integration

Coordinating afforestation with sustainable mobility systems, urban drainage and water networks, and public-space regeneration—so that vegetation functions as part of a broader ecological–infrastructural system.

3.

Design-Led Spatial Quality

Employing landscape and architectural design to structure planting layouts, define thresholds and interfaces with historical and archaeological sites, and deploy Nature-Based Solutions that enhance perceptual, social, and environmental performance.

4.

Social Engagement and Stewardship

Involving local communities, associations, and institutions in the co-design, care, and long-term maintenance of green spaces to ensure durability, identity, and shared ownership. These forms of engagement also constitute a prerequisite for long-term success, as stewardship structures help stabilize maintenance capacity and reduce the risk of ecological decline over time.

Within this framework, Serenissima Park emerges as a strategic testing ground. Identified as one of the 13 priority areas in the Metropolitan Forestry Plan, the site is defined by vacant and residual land, the presence of major mobility infrastructures (A24, high-speed rail, public transport corridors), and significant archaeological and landscape assets. These conditions create a unique opportunity to reframe afforestation as a form of green infrastructure: not simply the addition of tree cover but the construction of a network of ecological connections, pedestrian and cycling routes, public open spaces, and habitat systems (Figure 7, Figure 8 and Figure 9).

In this perspective, Serenissima Park becomes a demonstration site for a systemic model of urban afforestation in Rome—one in which vegetation is used to reorganize spatial relationships, support sustainable mobility, enhance heritage landscapes, and strengthen ecological continuity across the metropolitan territory. Its implementation, however, will depend on the city’s ability to ensure coordinated governance, long-term maintenance, and phased investment—conditions highlighted consistently across the international cases reviewed.

6. Serenissima Park: Research-by-Design Outcomes

6.1. A Strategic Edge Context

The Serenissima area forms a green wedge between the A24 motorway and the Milan–Naples high-speed railway line, parallel to Via Prenestina (Figure 10). Historically designated by the 1962 Rome Masterplan as the core of the Eastern Business District, the area has recently been placed under protection by the Ministry of Cultural Heritage due to its exceptional landscape and archaeological value.

Surrounded by the neighborhoods of Colli Aniene, Tor Sapienza, and Centocelle. The area is ~60 ha, with 5.76 ha earmarked for afforestation in the Metropolitan Forestry Plan of 2022 (Figure 11). It is both an urban threshold (between compact city and the countryside toward Tivoli) and a mobility node. However, it lacks structured public spaces—making it ideal to test landscape-based afforestation integrating ecology, mobility, and urban regeneration.

The area forms a mosaic of natural and anthropic environments: archaeological sites fallows, residual woodlots, wetlands, urban gardens, residential zones (including some informal occupation), depots, abandoned fields, and disused infrastructures.

Ecologically, it is a potential corridor between the Aniene River, the Tiburtina Hills, and the Roman countryside, stitching together fluvial and hilly ecosystems.

Surface-temperature mapping (Landsat 8) shows urban heat islands up to ~5 °C warmer than nearby districts, indicating the role of afforestation in local climate mitigation.

The site contains Rome’s largest Republican–Imperial necropolis, with more than 2000 tombs dated to the 2nd century AD along the ancient Via Collatina, in addition to a Roman villa in Via Scarpitti, the villa and mausoleum of Aquilius Regulus, agricultural casali, and an underground segment of the Aqua Virgo aqueduct. The INA-Casa district designed by De Renzi and Muratori frames part of the western boundary. The area also hosted, in 1892, the world’s first high-voltage AC transmission line from the Acquoria hydroelectric power station in Tivoli.

Today, urban gardens, wetlands, and spontaneous greenery coexist with vacant lands and illegal waste disposal. Three disused railway stations—Prenestina, Serenissima, and Togliatti—lie along the partly buried track, above which the GRAB cycling loop passes. The site lies at the center of the proposed East Rome Linear Park, connecting Porta Maggiore to Gabii, via Cervelletta Park, the Latomie di Salone, and the Aniene valley.

This constellation of heritage, ecological corridors, mobility infrastructures, and residual open space makes Serenissima Park a strategic testing ground for an integrated urban afforestation model.

In the design scenarios, planting structures are conceived to reinforce the spatial logic of the proposed corridors, with vegetation types arranged to support microclimatic regulation and ecological continuity. Rather than focusing solely on species’ physiological performance, the scenarios prioritize how different plant layers—trees, shrubs, and groundcovers—can be combined to build resilient vegetated systems that interact effectively with the site’s morphology and urban fabric [43].

6.2. Design Intent

GIS analyses highlight six elements:

• High ecological permeability due to non-built surfaces;
• Proximity to major parks (Aguzzano, Aniene Reserve, Centocelle);
• Potential for a continuous linear green system along main infrastructures, reconnecting isolated fragments.
• Opportunity to create transversal links with adjacent neighborhoods currently severed by the A24 and HSR;
• The need to integrate shaded cycling/walking routes, rail stations as urban nodes, archaeological enhancement (e.g., a large Roman necropolis between Via della Serenissima and Via Basiliano with remains of the ancient Via Collatina, the Aqua Virgo aqueduct, and a votive basin; >2000 tombs and a mausoleum), and attractive public spaces (Figure 12 and Figure 13);
• The analysis of the land registry lots has highlighted that the land ownership is predominantly public, thus facilitating the future construction process (Figure 14).

The approach for Serenissima Park is structured around five integrated strategies (Figure 15, Figure 16 and Figure 17):

• Ecological stitching—continuous vegetation between the Aniene Reserve and Centocelle Park via belts, tree rows, and multifunctional hedgerows;
• Green-blue infrastructure—tree systems paired with micro-basins and rainwater channels to support groundwater recharge and runoff control;
• Slow connections—shaded pedestrian and cycling routes linked to future metropolitan greenways and transit stations;
• Social and cultural spaces—areas for cultural, educational, sports, and recreational uses, leveraging proximity to schools and community centers; particularly significant is the archaeological presence;
• Adaptive afforestation—drought-resistant native species (holm oak, downy oak, Celtis, strawberry tree, privet, Rhamnus alaternus) to ensure long-term resilience. The selection of these species is grounded in the site’s Mediterranean thermo-xeric conditions, the heterogeneity of alluvial and compacted soils, and evidence demonstrating the superior drought tolerance, evapotranspirative cooling, and carbon-sequestration performance of native and naturalized taxa in Rome’s eastern peri-urban belt.

The design strategy proposes two complementary urban structures—Rambla Prenestina and Foresta Serenissima—which together reconfigure Serenissima Park as a public landscape for everyday life and intermodal mobility.

(a)

Rambla Prenestina

The existing rail trench produces a linear, underused strip lacking urban identity. The project transforms this axis into a Rambla, conceived according to the principle of the 15 min city. A continuous, partially shaded walkway, supported by slender steel columns, hosts

• An Electricity Museum (recalling the Acquoria-Serenissima transmission history);
• An Archaeological Interpretation Center;
• Community markets, cafés, and craft spaces;
• Sports fields, play areas, and event platforms;
• Direct station access and multimodal interchange nodes.

The Rambla acts as a multifunctional connector, where cultural heritage, everyday uses, and mobility infrastructure intersect, transforming the Serenissima and Togliatti stations into civic intermodal hubs.

(b)

Foresta Serenissima

The second component is a new urban forest composed of approximately 160,000 trees and shrubs, structured into four distinct landscape areas:

• Archaeological Park of the Necropolis
  An open woodland and interpretative landscape integrating the Roman funerary complex.
• Forest of Memory
  A civic woodland dedicated to remembrance and collective rituals.
• Hygrophilous Forest Enhancement
  Restoration of wetland species (Quercus robur, Fraxinus angustifolia) to strengthen biodiversity and protect aquatic avifauna.
• Via Scarpitti Cultural Landscape
  Landscape enhancement of the villa and casale system with platforms, walking paths, outdoor learning gardens, and ecological shading structures.

The forest is equipped with:

• Wooden platforms for performances and outdoor classrooms;
• Sports and play areas;
• A water basin and urban beach;
• A network of urban gardens connecting to Cervelletta Park;
• Continuous tree-lined promenades linking surrounding neighborhoods.

This system provides habitat continuity, supports mammal and bird species, and creates a public space for slow mobility and community life.

6.3. Systemic Role and Expected Outcomes

The Serenissima Park is conceived as the western gateway to the future Rome–Tivoli Eastern Greenway, a ~25 km ecological and cultural corridor reconnecting peripheral neighborhoods, archaeological sites, and natural systems. By integrating afforestation with mobility, heritage enhancement, and public-space regeneration, the project acts as a systemic territorial device rather than a localized intervention (Figure 18).

Expected medium-term outcomes (5–10 years) include:

• Urban afforestation: creation of approximately 160,000 new trees and shrubs, privileging drought-resistant native species to ensure long-term ecological resilience;
• Carbon sequestration: ≈230,000 tons of CO₂ absorbed annually through new woodland systems and improved soil carbon retention;
• Microclimate regulation: 2–4 °C reduction in average summer surface temperatures due to shading, evapotranspiration, and soil permeability;
• Sustainable mobility: implementation of ~2 km of internal slow routes, with planned extensions connecting to:

  -

  the 23 km extra-urban pathway toward Tivoli;

  -

  the 44 km GRAB cycling network encircling the city;

• Social impact: potential direct benefit to ~400,000 residents in Municipalities IV and V, through increased access to equipped public spaces, shaded routes, and community programs;
• Public health benefits: reduction in perceived social isolation and stress through regular exposure to nature, shared outdoor activities, and walkable everyday landscapes;
• Ecological connectivity: establishment of continuous habitat corridors between the Aniene River Reserve, Centocelle Park, Cervelletta Park, and surrounding green patches, enabling biodiversity continuity across the eastern metropolitan sector.

These projected outcomes are based on conservative ecological assumptions consistent with the site’s Mediterranean climate, the use of drought-resistant native species, and the establishment of continuous maintenance regimes, which constitute prerequisites for ensuring long-term performance and for avoiding declines in canopy survival, cooling capacity, and ecosystem-service delivery.

Additional spatial and cultural outcomes include:

• Enhancement of archaeological and historical landscapes: integration and interpretation of two Roman villas and the largest Republican necropolis, reactivated as accessible cultural public spaces;
• Wetland reinforcement: ecological upgrading of the humid area, supporting hygrophilous plant communities and aquatic avifauna;
• Intermodal civic infrastructure: renovation of the Serenissima, Prenestina, and Togliatti stations as multifunctional hubs linking mobility, public services, and leisure;
• Memory and identity landscapes: creation of a Forest of Memory, dedicated to collective remembrance and civic rituals;
• Productive and social ecologies: valorization of urban gardens (orti urbani) as spaces of community management, education, and local food practices.
• Public realm continuity: creation of a tree-lined urban promenade capable of linking squares, schools, and local services through shaded pedestrian and cycling networks;
• Everyday leisure and community uses: development of water basins and seasonal bathing areas, playgrounds, and sports and gathering platforms, enhancing intergenerational inclusivity and year-round usability;
• Urban forestation networks: coordinated afforestation across adjacent neighborhoods, ensuring continuity beyond park boundaries.

6.4. Significance

Serenissima Park demonstrates how urban afforestation can function as design-driven green infrastructure, reorganizing territory through:

• Ecological connectivity;
• Sustainable mobility;
• Heritage interpretation;
• Community stewardship.

Rather than adding tree cover, the project uses vegetation to transform the spatial logic of the city, producing environmental performance and public space quality simultaneously. Its long-term significance, however, depends on the capacity to secure stable maintenance, coordinated governance, and the ecological conditions assumed in the design scenarios, which are essential to sustain canopy survival, cooling effects, and biodiversity continuity over time.

7. Conclusions

7.1. General Considerations

When understood as an integrated design instrument rather than a compensatory ecological measure, urban afforestation can play a decisive role in sustainable metropolitan transformation. It is not merely a strategy for carbon reduction but a spatial and cultural project capable of reshaping relations between nature, infrastructure, and everyday life.

The analysis of policies in Lazio and Rome shows that, despite significant investments, current initiatives remain predominantly quantitative and fragmented, with success still measured primarily through tree counts and CO₂ absorption metrics. Qualitative aspects—spatial continuity, landscape identity, and social accessibility—are only marginally addressed.

In contrast, international experiences such as Medellín’s Green Corridors, Philadelphia’s Philly Tree Plan, and Milan’s Forestami demonstrate that afforestation can become a driver of environmental justice, public-space regeneration, and collective stewardship when supported by

• Shared governance frameworks;
• Robust monitoring and mapping tools;
• Participatory and community-based management;
• A clear design vision for landscape continuity.

These cases also show that long-term effectiveness depends on stable maintenance regimes, coordinated governance, and ecological assumptions aligned with local climatic and soil conditions, which together constitute essential prerequisites for sustaining performance over time.

7.2. Considerations on the Roman Context

In Rome, Serenissima Park offers a concrete opportunity to apply these principles within a complex and stratified urban–peri-urban landscape. The proposed Rome–Tivoli Eastern Greenway introduces a systemic green infrastructure connecting archaeological sites, wetlands, neighborhoods, and mobility networks.

Here, afforestation is conceived as territorial architecture:

• Structuring ecological connectivity across fragmented spaces;
• Enhancing slow mobility networks;
• Integrating heritage layers and memory landscapes;
• mproving climatic comfort and ecological performance;
• Generating new forms of public life.

Emerging operational priorities include the following:

• A unified metropolitan green framework to overcome administrative fragmentation and align regional, metropolitan, and municipal policies;
• Integration with sustainable mobility and urban-regeneration strategies, enabling afforestation to act as spatial infrastructure rather than isolated planting;
• Co-management and stewardship models involving residents, schools, and associations in maintenance and monitoring;
• Evaluation metrics that combine ecological, spatial, and social performance, alongside traditional environmental indicators;
• Applied research collaborations, such as those developed within NBFC Spoke 5, to link scientific data, ecosystem-service assessment, and design experimentation.

In this perspective, Serenissima Park becomes a prototype for a metropolitan model—where vegetation is used to reconstruct continuity, identity, and public meaning across the city.

7.3. A Laboratory of Applied Research

Serenissima Park acts as an applied research laboratory for testing integrated afforestation strategies in contexts characterized by the following:

• Archaeological constraints, which require selective planting and spatial calibration;
• Residual and infrastructural landscapes, where afforestation must negotiate mobility systems and brownfield conditions;
• Socio-environmental vulnerability, where green infrastructure supports health, identity, and equity.

Field surveys and simulations conducted within NBFC Spoke 5 enabled the assessment of biodiversity indicators, microclimatic effects, and ecosystem-service potential, while informing planting eligibility and heritage protection parameters. The methodology developed here can be extended to other urban-edge territories, contributing to continuous urban and peri-urban forest systems. In line with Clemente’s strategic vision for Rome [44,45], street trees may function as linear ecological infrastructures, reconnecting fragmented green networks throughout the metropolitan fabric.

7.4. Limitations and Future Developments

The research is limited by the following:

• The heterogeneity of available datasets across institutions and programs;
• The short temporal horizon of recent afforestation initiatives;
• The absence of consolidated post-implementation monitoring.

The proposed model can therefore only be fully evaluated through built implementation and long-term observation.

Future research will focus on

• Progressive realization of the Serenissima Park interventions;
• Continuous monitoring of ecological and social indicators;
• Replication across comparable Roman and metropolitan contexts.