1. Introduction
Urban green infrastructure (UGI), which includes parks, community gardens, forests, and corridors along waterways, provides important connections between communities and nature [
1]. Urban green infrastructure planning aims to develop green space networks in limited spaces in compact cities [
2]. These areas provide numerous ecosystem services, and have contributed to increasing physical activity, improvement in mental health, and improved socialisation of the community residents [
3]. Urban green infrastructure helps cities increase their resilience to climate change and to improve their attractiveness by offering a cleaner and healthier environment [
4].
Environmental justice occurs when green infrastructure is equally distributed, without discrimination, within a city. Cities are complex social-ecological systems, and the decisions and processes responsible for today’s UGI availability have occurred over centuries; for this reason, it is difficult to determine all the factors that affect the quality of urban green infrastructure. For example, along with the environmental justice issues, the location of a city, related to morphological and climatic conditions, such as water availability, proves to be another strong characteristic that affects the availability of urban green spaces. Although it is well-established that the relationship between green infrastructure and the urban environment is essential for improving wellbeing and population health [
3], in many developed countries, the availability of green space is limited, or its distribution across the city is uneven.
Some authors [
5,
6] consider that the availability of green spaces in European cities may be directly related to their geographical location, with higher amount of public green spaces found in Northern and Central European countries than in Mediterranean ones. Furthermore, it is also recognised that the distribution of public green space is related to the location of different social classes [
7]. This means that socioeconomically deprived sections of society, such as low-income groups or ethnic minorities, often also have less access or are deprived of access to green spaces, compared to the rest of the population [
8].
Low accessibility to UGI in some areas of a city or for some demographic groups is, nowadays, a problem of environmental justice. For this reason, projects have been developed with the aim of rehabilitating degraded neighbourhoods and increasing the amount of green space in order to improve wellbeing and environmental justice. The implementation of those projects has been successful when they are integrated into the existing green infrastructure network and designed according to the needs of the inhabitants. Conversely, paradoxical interventions have resulted in the phenomenon of green gentrification.
Green gentrification has been observed when urban regeneration projects attract investment around new, high-quality public green space, and become an attraction for social classes with higher income and greater purchasing power. The demand for accommodation near these new recreational spaces promotes the renovation of dwellings or the construction of new ones and, therefore, the house process, rental values, and living costs increase. Consequently, the original residents are forced to relocate to cheaper areas of the city, but they lose the benefits of the public green spaces that were provided to improve their wellbeing. Green gentrification is, however, a difficult phenomenon to study since it is only visible in the long term [
9].
Estonia is one of the greenest countries in Europe [
5], but there are green infrastructure differences between the Soviet-era housing districts and the districts developed both before and after that period (1944–1991). Research into the inequalities of post-Soviet Union has focused on the quality of buildings, but ignored the accessibility of public green spaces. Generally, accessibility to public green spaces is lower in Mediterranean cities compared with North European ones [
10,
11]. Faro is one of the Portuguese cities with the least green space per inhabitant (8 m
2) [
9,
12]. Thus, there are two pertinent reasons for comparing the accessibility of public green space in Tartu, Estonia; and Faro, Portugal. Both cities are similar in terms of population size (small cities) and have similar social and cultural dynamics, however, they are distinct geographically and morphologically.
This article explores the notion of environmental justice in urban green infrastructure and how to avoid green gentrification. The overall aim of the study was to investigate the accessibility of public green spaces in a Nordic/Baltic and a Mediterranean city, and addressed the following research questions: Are there districts with more and less accessibility in Tartu and Faro? Are the minority groups and time of construction related to the accessibility of the public green spaces? The hypothesis of this study was that “there is no environmental justice in the distribution of the public green spaces in both Tartu and Faro”.
4. Results
The PGS per inhabitant was calculated in each district for both cities.
Table 1 presents the area of gardens, buildings, trees, and grassland per district of Tartu to characterise the relative relation of green space and urbanised area in each district. There were two main types of buildings in Tartu city that are directly related to the area of yards. For example, the districts of Tammelinn, Ihaste, and Karlova have a higher proportion of yards, and the majority of the buildings in these districts were single-family houses.
Table 2 presents the location of ethnic minorities in the city, and compares this with the distribution of public green spaces in the city. The districts with higher numbers of ethnic minorities, mainly Russians, were Jaamamõisa (53% of Estonians, 39% of Russians, and 8% of other nationalities), Annelinn (67% of Estonians, 28% of Russians, and 5% of other nationalities), and Ropka tööstusrajoon (80.1% of Estonians, 16.4% of Russians, and 3.4% of other nationalities). On the other side, the districts with fewer ethnic minorities were Variku, Tähtvere, Tammelinn, and Karlova.
Table 3 presents the number of inhabitants and area of each district of Faro. The number of immigrants has been decreasing over the years. There were 11.2%, in 2010, and 9.9% by 2016. However, there is no available data relating ethnic nationality with place of residence. Despite this, it was possible to identify the Roma minority of Faro as being located in four main neighbourhoods: in Penha, in industrial area, and in the periphery. They live in social housing estate neighbourhoods, or in prefabricated houses and containers, built in areas far from the city centre and with difficult access to services, which seems to reinforce the segregation of the communities [
79]. Furthermore, the area of the dwellings was very small, without adequate conditions for people with disabilities or elderly people, and without common or leisure spaces. These neighbourhoods have small entrances, and the composition forms a labyrinth, which makes it appear that the neighbourhood is “closed” to the rest of the city space [
80]. There are still other Roma clusters of small dimensions, in Faro, that live in miserable conditions in abandoned old houses or containers.
Table 4 for Tartu and
Table 5 for Faro show the results of availability and accessibility to PGS of at least 1 ha in these cities. In Tartu, Tähtvere was the district with the greatest area of PGS per inhabitant, around 146 m
2 per habitant. The districts of Maarjamõisa and Supilinn also had a significant area of PGS per inhabitant, 126 m
2/inhabitant and 79 m
2/inhabitant, respectively. Conversely, Karlova was the district with the lowest area of PGS per habitant, about 1 m
2/inhabitant. Also, the districts of Ihaste, Jaamamõisa, Ropka, Ränilinn, Tammelinn Vaksali, Variku, and Veeriku had less than 10 m
2 per inhabitant. In Faro (
Table 5), the majority of districts had less than 10 m
2 of PGS per inhabitant. The exception was district 8, “Figuras and Urban Periphery”, with about 31 m
2/inhabitant.
Figure 4 shows the map of accessibility to PGS from each residence, using the walkability method, for the city of Tartu, which was quantified in
Table 4. It can be seen that using the 300 m and 500 m distance, and two different sources of data, 45% of the city residents have access to PGS within a seven-minute walk. Meanwhile, the same percentage (45%) was observed also for the city of Faro in the buffer of 500 m (
Figure 5 and
Table 5). This result shows that even though the South European city had much less available PGS per inhabitant, the accessibility was the same as in the very green, but more spread out, city of Northern Europe.
According to
Table 4, it is possible to see that the districts with greater proportions of accessible area were Supilinn, where the accessible area covers the district’s total area, for both distance buffers; Kesklinn (83%, using 300 m buffer and 96% using 500m buffer); Maarjamõisa (78% and 99%, respectively), and Tähtvere (72% and 93%, respectively). The districts with lower proportions of accessible area to PGS were Jaamamõisa and Variku, without accessible areas in either district; Ränilinn with only 2% considering a 300 m buffer and 16% considering a 500 m buffer; Veeriku with 6% and 16% respectively; and Ihaste with 4% and 11%, respectively. It is important to look at the percentage of each district, rather than the total accessible area of PGS, because it considers the total area of each district.
Figure 5 shows the map of accessibility to PGS from each residence using the walkability method for the city of Faro, which was quantified in
Table 5. It was revealed that the districts with higher proportions of accessible public green spaces were district 6 (Alto de Santo António) with 39%, using the 300 m buffer; and 70%, using the 500 m buffer; and district 8 (Figuras) with 35% and 51%, respectively, of the district’s total area. On the other hand, the districts with lower proportions of accessible area were district 1 (Old Town and Historic centre) with only 23% using the 500 m buffer and district 7 (Penha) without any residence accessible within a 7-min walk to the PGS.
According to the grid method using the 300 m and 500 m buffers, the Tartu districts of Annelinn and Karlova had between 101 and 250 m2 of accessible PGS per inhabitant, and the remaining districts had over 251 m2 accessible PGS per inhabitant. Using the same method in Faro, it was revealed that, for the 300 m buffer, the districts 5 and 8 had more than 251 m2 of accessible PGS per inhabitant, the districts 2 and 6 had between 101 and 250 m2 per inhabitant, and the districts 3 and 4 had between 31 and 100 m2 per inhabitant. The Old Town historic centre and Penha districts had no PGS. Considering the area of 500 m buffer, the districts 6 and 8 had more than 251 m2 of accessible PGS, the districts 1, 2, 3, and 6 had between 101 and 250 m2 of accessible PGS per inhabitant, and district 4 had 31–100 m2 per inhabitant of accessible PGS. Penha was the only district without any accessible PGS, even within 500 m walking distance.
5. Discussion and Proposal for New Green Infrastructure
According to the evolution of the land use and occupation, it was confirmed that there was a significant increase in the public parks and green areas of Tartu, between 1998 and 2000. During the following years, since 2000 until 2017, the total area of public parks and green areas ranged between approximately 330 and 400 ha of total area, with their maximum value in 2016. In 2017, the total area of public parks and green areas (389 ha) corresponded to 10% of the city’s total area. The total area of high-quality PGS was 202 ha. Meanwhile, in the present study, we considered only the high-quality PGS with more than 1 ha.
Analysing the data on ethnic minorities, it could be seen that the districts with the highest percent of ethnic minority residents (Annelinn, Jaamamoisa, and Ropka tööstusrajoon, with 28%, 39%, and 16.4% of Russians, respectively) were developed mostly during the Soviet era and, for that reason, the predominant typology of buildings were multi-storeyed panel housing blocks. Nowadays, those housing blocks are of poorer quality compared to the single-family house, as described in the literature review, confirming that the majority of ethnic minorities in Tartu, mainly Russians, live in the districts with a declining quality of life.
The World Health Organization (WHO) recommends that there should exist at least 9 m
2 of green space per person, but it recommends 15 m
2 of accessible green space while, the ideal amount, according to the same organisation, would be 50 m
2 [
49]. Also, in Brazil, the index of 15 m
2/inhabitant is recommended to promote a good quality of life [
81]. The United Nations sustainable development goal 11, regarding sustainable cities, defines, as an indicator, the “adequate open public space in cities”, and has as a target, by 2030, to provide universal access to safe, inclusive, and accessible green and public spaces, in particular, for women and children, older persons, and persons with disabilities [
82].
Comparing the UN reference point with the values in the
Table 4 for Tartu, it is possible to determine that the districts of Ihaste, Jaamamõisa, Karlova, Ropka, Ränilinn, Tammelinn, Vaksali, and Veeriku had a lower area of PGS per inhabitant than that suggested by the World Health Organization. Compared with the same source, only Maarjamõisa, Supilinn, and Tähtvere had over the ideal value of PGS per habitant. However, in this analysis, it was important to note that most districts with low value also had high areas of private gardens, as shown in
Table 1.
In Faro, the majority of districts had less than the amount recommended by the World Health Organization [
49], such as Figuras district, which had 31.44m
2 per habitant, below the ideal area of 50 m
2. According to Barreira et al. [
83], some of the reasons for residential satisfaction and city attractiveness were the availability of green areas and opportunities for leisure activities in open-air public space. Green space availability can be related to people’s perceived happiness and general health, while having green space nearby appears to reduce the incidence of heart disease, obesity, and depression [
84,
85]. Moreover, green infrastructure may enhance city resilience to climate change by means of ecosystem services’ improvement [
20], and assist in climate change adaptation, which is one of the factors for future city growth [
86]. According to Panagopoulos [
87], city climate change adaptation is a major issue in environmental justice for vulnerable urban populations, like the elderly, minorities, and people of low socioeconomic status, while health benefits and resilience to climate change appear to be stronger for vulnerable groups.
Regarding the accessibility to PGS in Tartu, the results revealed that the districts with less accessible areas of PGS were Jaamamõisa, Variku, Ränilinn, Ihaste, and Veeriku. However, it would be expected that Annelinn and Ropka tööstusrajoon would be also included in the districts with less accessibility of PGS since, according to a survey [
88], the inhabitants consider them to be districts with a lower quality living environment, as well as Jaamamõisa and Ränilinn. Still, when critically observing the map in
Figure 4, it could be verified that, in Annelinn, which shows a high percentage of accessible area of PGS (52% for the 500 m buffer), a significant part of this area included only few dwellings, while the grid method showed that Annelinn, due to its high population density, had less accessible area of PGS per inhabitant.
While Tartu had a greater area of public green spaces, in total, than Faro, the percentage of accessible area to the PGS was similar in both cities (45%). However, when considering the 300 m distance buffer, Tartu had better access to PGS than Faro (30% instead of 25%). Furthermore, the grid method showed that the accessible area per habitant was higher and more uniform in Tartu than in Faro. The greater accessibility in Tartu could be accounted for by the geographic location and cultural differences. As noted in many studies [
5,
6], there is a tendency for northern European countries to have greater availability of green spaces, due to a favourable climate compared with Mediterranean countries. Nonetheless, the culture also influences the use of public spaces. For example, Thompson [
89] notes that, in Mediterranean countries, there was a long tradition of strolling in the street, while, in Nordic countries, the urban park is the main element of public space, and it plays an important role in social relations. The importance and the use given to PGS can influence the availability of those spaces in the city. However, even if in Mediterranean countries the PGS was less widely used than in the Nordic countries, it was still important to note that the presence and associated ecosystem services of such spaces in the city are essential to securing a high level of quality in urban living.
5.1. Tartu Masterplan (Linna Üldplaneering)
Table 6 summarises the results presented in
Table 4 and
Table 5, and considers the plans for Tartu 2030 and Faro up to 2030. In Tartu, a significant increase in public green space area, around 160 ha, was verified. Consequently, an increase in the accessible area to these spaces is expected. This plan predicts that the total accessible area in Tartu will increase from 30% to 68%, and from 45% to 86%, using a 300 m and 500 m distance buffer, respectively.
On the implementation of the Tartu Masterplan by 2030, the districts with a high proportion of accessible area to PGS will be Supilinn, Jaamamõisa, Kesklinn, and Ränilinn, while the districts with a lower proportion will be Tammelinn, Veeriku, and Ropka tööstusrajoon, for both distance buffers.
Nevertheless, the data per district shows that the increase in the PGS and, consequently, in the percentage of accessible area, would result primarily from two transformations in the landscape of the city: (1) an empty area, without any existing function, could be transformed into a PGS of high quality, or (2) an existing PGS of low quality could be transformed into a new one of high quality.
Variku and Ihaste are examples of those planned transformations (
Figure 6). In Ihaste, the area of PGS should increase by 46 ha; however, this area represents existing green spaces of low quality and without mobility conditions. In turn, the PGS area of Variku should increase by 10 ha, which would be occupied by a new park in an area that currently does not have any function. According to Tartu Masterplan, this new public space will include a dog walking area and recreational, sports, and cultural facilities.
5.2. Proposal for Faro
The results of the present study revealed that some districts in Faro were without accessibility to PGS, which allows us to confirm that there was an unequal distribution of PGS in this city. This fact justifies the necessity of suggesting some strategies for increasing the amount of PGS and, consequently, promoting the equal distribution of these areas across all Faro’s districts. The following map (
Figure 7) identifies the location of the main problem areas in the city, and proposes solutions for those issues.
The most important intervention is the development of an urban park in Penha and the redevelopment of the industrial area, to promote the connection between inhabitants and the Ria Formosa. For the most compact districts—1, 2, and 3—without space to develop new green areas, construction of green roofs and green walls on public buildings, together with the planting of trees along streets, was proposed to promote the connection of existing green areas and the continuity of ecological flows. For disaster risk reduction and climate change adaptation, soil restoration and substitution of the pavement with permeable materials, in stream margins with risk of flash flooding, was proposed.
In the Old Town area, included in district 1, the rehabilitation of private abandoned yards and urban agriculture allotments was proposed, to establish a connection between these areas with the existing PGS enhancing the city resilience [
90]. Those abandoned private yards, being located in a historic district and close to the “Ria Formosa”, have a high ecological and recreational potential, especially for the inhabitants of the old city that are mostly elderly. It was also proposed to convert the current railway line to a bike path and green corridor. These proposals must integrate the ideas, expectations, and suggestions of the inhabitants [
91] and of the visitors [
92], which will be part of future research.
5.3. Green Gentrification
Taking the definition of green gentrification, as discussed earlier in the paper, into account, and comparing the Tartu and Faro cases, in our view, this phenomenon is more likely to occur in Faro than in Tartu, since the need to develop new green spaces is greater in Faro than in Tartu. In addition, Tartu presents, for the most part, a typology of buildings that allows for the presence of private gardens as an alternative to the need for PGS by the residents of these single-family houses.
In Faro, the abandoned industrial area, included in district 5, has been set aside for an urban redevelopment project, as it has direct contact with the Ria Formosa landscape, is close to the city centre and the airport, and forms an extensive area. Municipal plans refer to the implementation of a future project to include a marina and a tourist-residential area with extensive PGS, that will occupy 29 ha. The municipal authority believes that this project will not compromise the operation of the current commercial port and the high environmental qualities that characterise that landscape, meanwhile estimating that this project has a total potential value of 300 million euros for the city [
93]. Meanwhile, this highly polluted area, with residents mostly of Roma ethnicity living in state housing, represents a case of social exclusion in the city, with problems of poverty, crime, and lack of security. It is expected that the implementation of a large urban regeneration project in this residential district, inserted in this old industrial area since 1970, will directly affect the life of the residents of the state housing, since they would be forced to be relocated to another part of the city. Thus, this area has a high likelihood of green gentrification.
In the case of the Tartu, it is thought that the neighbourhoods built during the Soviet period are where the phenomenon of eco-gentrification may exist since, as stated in the literature, they present poorer conditions than others [
94]. However, the fact that there are a wide variety of areas suitable for the construction of new public green spaces, and because Tartu is considered a fairly balanced city, the likelihood of green gentrification occurring is reduced.
A limitation of this study is the fact that gentrification might be a result, as well as a cause, of green space development. As our data do not allow the assessment of causal relationships over time between gentrification and new green space development, it remains difficult to elaborate further on the situation. It was not possible to evaluate the existence of green gentrification, in part, due to lack of data about the income of households, over time, per district, for both cities. Also, in Faro, although an area with risk of gentrification was identified, it was not possible to develop a method of calculating this phenomenon. For future research, to evaluate the green gentrification phenomenon, we suggested that additional socioeconomic data should be obtained and applied in a Markov Model of Urban Change in time and space, as was done by Royall and Wortmann [
95].
6. Conclusions
Urban PGS perform important functions that directly affect the quality of life and wellbeing of urban inhabitants. They are considered key elements in improving the quality of life and creating an appropriate framework for sustainable cities [
96]. For this reason, such public spaces should be equitably distributed throughout the city, in order to provide ecosystem services to the entire population. Accessibility and availability of PGS can be valuable indicators of environmental injustice in neighbourhoods within a city, information which may help to promote future urban regeneration projects in areas with the highest needs. The quantitative indicators used to estimate availability and assess urban green infrastructure can be applied widely in comparisons of any city, or of districts within city [
97]. Meanwhile, one limitation of the study was the inability to consider the quality of green space, as a result of lack of data.
Based on the analysis of urban growth and indicators related to the distribution of PGS, it was found that, in both cities, there was a relationship to the ethnicity of the inhabitants. Moreover, the study between Tartu and Faro showed that the geographical location within Europe can influence the urban space availability with 6.2 m2/inhabitant in Faro and 20.8 m2/inhabitant in Tartu. Meanwhile, the accessibility to PGS was 45% of residences in both cities, because Tartu is low density and Faro is a compact city.
Tartu ethnic minorities, mainly Russians that live in areas developed during the Soviet period (Jaamamõisa, Ropka tööstusrajoon, and Annelinn), were those who live in districts classified as having lower quality of the living environment [
88]. Meanwhile, the walkability distance method revealed that districts Variku, Ränilinn, and Veeriku also had low accessibility while, for Annelinn, all indicators were close to the city average (14 m
2/inhabitant, 32% accessibility within 300 m, and 52% within 500 m). From the above, it is concluded that there is a strong relationship between the ethnicity, type of urbanisation, and the quality of the living environment, that includes the availability and accessibility to PGS, but is not confirmed in every district. Despite this, the degree of environmental injustice in Tartu was lower than Faro.
The minorities of Faro, in particular, the Roma communities, were located in districts without (Penha 1.22 m2/inhabitant) or with low access to public green spaces (Bom João 4.76 m2/inhabitant). Furthermore, those neighbourhoods may suffer gentrification processes in the future, due to the implementation of large-scale urban regeneration projects aiming to satisfy the tourist demands of the region. Meanwhile, it was not possible to evaluate the green gentrification phenomenon, because this is a long process, beyond the period of this research, and it was not clear if gentrification might be a result, as well as a cause, of green space development.
In Faro, Figuras, which is the most recently developed district and with inhabitants of higher socioeconomic status, showed greater availability and accessibility to green areas (31.44 m2/inhabitant, 35% accessibility within 300 m, and 51% within 500 m). This district includes both of the new PGS established in Faro in recent decades (Parque Ribeirinho and the Parque de Lazer). In Faro, being one of the Portuguese cities with the least green space per inhabitant, it is an urgent task to focus on planning new green infrastructure, integrating the needs and opinions of residents into proposals, in order to increase the accessibility to PGS and secure environmental justice in the city.
The comparison between Tartu and Faro suggests that the geographical location influenced the availability and quality of green areas in the city, as well as social cohesion itself. In addition, it is expected that the implementation of “Tartu Linna Üldplaneering”, which reflects a scenario for the city’s public green spaces by 2030, will considerably improve the city’s environmental justice. The proposal for new green infrastructure in Faro may decrease the verified environmental injustice.
Accessibility to PGS in cities, and the identification of the most problematic areas, should be integrated into sustainable urban planning proposals. The outcome of this study could provide good advice for balancing green space distribution within city neighbourhoods in similar cities of other countries. In addition, future actions should be conducted with the aim of monitoring the long-term ecosystem services provided by green spaces, and for early identification of green gentrification risks.