How do the green components of urban green infrastructure influence the use of ecosystem services? Examples from Leipzig,Germany

Landscape Ecology - The pressure on remaining open spaces of urban green infrastructure (UGI) is high due to increasing urbanization and the multiple requirements of a diverse urban population....     

The domestic garden – Its contribution to urban green infrastructure

Domestic gardens provide a significant component of urban green infrastructure but their relative contribution to eco-system service provision remains largely un-quantified. ‘Green infrastructure’ itself is often ill-defined, posing problems for planners to ascertain what types of green infrastructure provide greatest benefit and under what circumstances. Within this context the relative merits of gardens are unclear; however, at a time of greater urbanization where private gardens are increasingly seen as a ‘luxury’, it is important to define their role precisely. Hence, the nature of this review is to interpret existing information pertaining to gardens/gardening per se, identify where they may have a unique role to play and to highlight where further research is warranted. The review suggests that there are significant differences in both form and management of domestic gardens which radically influence the benefits. Nevertheless, gardens can play a strong role in improving the environmental impact of the domestic curtilage, e.g. by insulating houses against temperature extremes they can reduce domestic energy use. Gardens also improve localized air cooling, help mitigate flooding and provide a haven for wildlife. Less favourable aspects include contributions of gardens and gardening to greenhouse gas emissions, misuse of fertilizers and pesticides, and introduction of alien plant species. Due to the close proximity to the home and hence accessibility for many, possibly the greatest benefit of the domestic garden is on human health and well-being, but further work is required to define this clearly within the wider context of green infrastructure.     

Can we integrate ecological approaches to improve plant selection for green infrastructure?

Modern cities are dominated by impervious surfaces that absorb, store and release heat in summer, create large volumes of runoff and provide limited biodiversity habitat and poor air quality can also be a health issue. Future climate change, including more frequent and extreme weather events will likely exacerbate these issues. Green infrastructure such as parks, gardens, street trees and engineered technologies such as green roofs and walls, facades and raingardens can help mitigate these problems. This relies on selecting plants that can persist in urban environments and improve stormwater retention, cooling, biodiversity and air pollution. However, plant selection for green infrastructure is challenging where there is limited information on species tolerance to heat and water variability or how these species can deliver multiple benefits. Therefore, we draw on research to illustrate how plant performance for green infrastructure can be inferred from plant attributes (i.e., traits) or from analysis of their natural distribution. We present a new framework for plant selection for green infrastructure and use a case study to demonstrate how this approach has been used to select trees and shrubs for Australian cities. We have shown through the case study and examples, how plant traits and species’ natural distribution can be used to overcome the lack of information on tolerance to both individual and multiple stressors; and how species contribute to the provision of benefits such as stormwater retention, cooling, biodiversity and air pollution mitigation. We also discuss how planting design and species diversity can contribute to achieving multiple benefits to make the most of contested space in dense cities, and to also reduce the risk of failure in urban greening.     

Equally green? Understanding the distribution of urban green infrastructure across student demographics in four public school districts in North Carolina,USA

Green infrastructure (GI) provides a suite of ecosystem services that are widely recognized as critical to health, well-being, and sustainability on an urbanizing planet. However, the distribution of GI across urban landscapes is frequently uneven, resulting in unequal delivery of these services to low-income residents or those belonging to underserved racial/ethnic identities. While GI distribution has been identified as unequal across municipalities, we investigated whether this was true in public schoolyards within and among urban school districts. We examined schoolyards in four metropolitan areas of diverse socio-economic and demographic compositions in North Carolina, USA to determine if they provided equal exposure to GI, then compared whether this was true of the broader urban landscape. We first classified the land cover of elementary schoolyards and their neighborhoods, then used bivariate and multivariate approaches to analyze the relationships between GI (i.e. tree canopy cover and total GI) and the socioeconomic status and race/ethnicity of the schools and surrounding neighborhoods, respectively. We found that the extent of tree canopy cover and total GI in schoolyards was unrelated to the socioeconomic status and the race/ethnicity of students across the four school districts. In contrast, neighborhoods with lower socioeconomic status and larger populations of underserved race/ethnicity residents had less tree canopy cover and total GI. Although total GI was more evenly distributed in schoolyards, the extent of tree canopy cover and total GI in schoolyards was lower than that in the neighborhoods. This suggests opportunities for school districts to expand GI in schoolyards, leveraging their potential to increase ecosystem services to all children, from increased educational opportunities to improved mental, physical, and environmental well-being.     

Can you really see ‘green’? Assessing physical and self-reported measurements of urban greenery

Urban vegetation provides a wide array of services; yet, there is still a knowledge gap regarding the mechanistic processes behind urban vegetation–human well-being relationships. Two main approaches have been used to assess urban greenery associated with human well-being: physical and self-reported. We here assessed the associations between physical (green view index–GVI, green cover–GC) and self-reported measures (perceived visible greenery–PVG) of the streetscape greenery of two southeastern Mexican settlements (Xalapa, Coatepec). Our results show that both sites have considerable GC (Xalapa = 37.2%, Coatepec = 47.4%). We found a clear association between GVI and GC in Xalapa, but none in Coatepec. The latter was due to an important proportion of the vegetation of Coatepec being mainly constrained at block interiors, obstructed by walls. Regarding the self-reported measure, our results show an important discrepancy in relation to one of the physical measures (GVI), assessed through PVG/GVI ratios. In general, respondents tended to overestimate greenery, with greater overestimations related to GVI values <10%. Among the assessed respondent traits (gender, education level, live and/or work in neighborhood, time living and/or working in neighborhood), we found none to explain variations of PVG/GVI ratios in Coatepec, but respondent age did relate, non-linearly, with PVG/GVI ratios in Xalapa. In a nutshell, our findings indicate that the assessed physical and self-reported measures capture different aspects of urban greenery that differ in their potential uses, with GVI representing a helpful tool to quantify visible greenery at eye-level; GC being a highly informative physical measure to assess the amount of public and/or private urban greenery; and PVG as a quick and inexpensive measure of people’s perception of visible urban greenery. Depending on the monitoring, managing, and/or planning goals, the use of the three assessed measures can provide an integral evaluation of urban greenery.     

Rethinking urban green spaces for urban resilience. Do green spaces need adaptation to meet public post-covid expectations?

Based on a social preference survey performed in Warsaw, we assessed the preferences toward alterations in urban green spaces (UGS) that should take place to ensure safe recreation. We identified how peoples’ personal characteristics are linked to the preferred changes to formulate recommendations for alterations addressing post-covid challenges while keeping the resident’s preferences in mind. We used 1–7 scorings of images of different types of urban landscapes, which we photomanipulated to represent varying levels of crowding, followed by questions regarding recreational behaviour, anxiety towards COVID and preferred changes. Various urban landscapes were, on average, comparably suitable for recreation, only highly urbanized landscapes receiving lower scorings. The respondents declared that vegetation density and overall share of vegetation were of the highest importance in assessing images and claimed that crowding had little effect on their preferences. Those statements were inverse to their choices when assessing recreational preferences based on images: the presence of people in all cases decreased assessment of the scenery. There was a clear respondents’ need for more wild and cultivated vegetation and more places for spending time in UGS. Any repressive actions by distancing people spatially in UGS, isolating seniors or introducing entry limits did not meet social approval. We also identified two major behavioural patterns: people who were primarily driven by fear of COVID-19, visiting green spaces closer to their homes and having less need for UGS alterations. The second group was those frequently visiting UGS who did not reveal fear of COVID-19, those who did not favour wide paths or the importance of UGS located nearby, and opted for more wilderness. These two approaches to recreation are likely to persist after the pandemic, which supports the need to increase UGS diversity.     

The green walk—An analysis for evaluating the accessibility of urban green spaces

The importance of urban green spaces in providing ecosystem services to the population is increasingly being recognised by scientists, policy makers and the general public. Across cities, urban planners are seeking to reconcile the location of urban green spaces and accessibility of the public. The main aim of our paper is to assess the accessibility of urban green spaces and to identify perceived benefits along the travel route to urban green spaces, starting from a selected case study in Romania. We started from a spatial analysis of a service area for an urban park in Bucharest (Tineretului). With the help of network analyst in ArcGis Pro we established the boundaries of the service area (using urban park boundaries, street network, traffic restrictions) and applied two methods of travel to the park (walking and cycling). We applied a survey to 202 respondents, collecting information on the routes and methods of reaching the park, as well as the perceived benefits and disservices of selecting the preferred method and route. The main results revealed different patterns delimited by a number of criteria: age (elder population preferred public transport and shaded routes), income (people with higher incomes selected travelling by car and accessing elements with parking facilities), group structure (people with children selected routes perceived as safe). This type of analyses can represent useful instruments for urban planners in developing and managing urban green spaces in close relation with neighbouring spaces and facilities.     

How is quality of urban green spaces associated with physical activity and health?

This study investigates the associations between quality of urban green spaces (UGS), self-reported physical activity (PA), and health indicators in Aydın, Turkey. Data was collected through a survey with 420 participants. The associations between quality of UGS, self-reported frequency and duration of PA, and stress, mental health, and physical health were examined with multivariate linear regression while controlling for confounding factors. Results showed that nearest distance to UGS and quality of UGS (i.e. maintenance and cleanliness) were associated with increased frequency of PA. Higher frequency of PA was related to less stress and better mental health and longer duration of PA was associated with better physical health. In addition, large and open/visible UGS were associated with better physical health. The findings also showed that stress mediates the relationship between PA and mental health. Results suggest that providing large, visible as well as clean and well-maintained UGS close to people's homes may be an effective strategy to improve PA and people's health.     

Can urban green space cure homesickness? Case study on China poverty alleviation migrants in Anshun,Guizhou

With the implement of China's ex-situ poverty alleviation resettlement (ESPAR) policy, nearly 10 million rural population have relocated with a better living condition in a short period of time, most of which have migrated to urban areas. The living environment and lifestyle of the poverty alleviation migrants (PAMs) have undergone dramatic changes, the resulting mental health problems may seriously affect their social integration and well-being. In particular, homesickness is a prevalent mental problem among the PAMs that demand prompt attention. Research indicates that longing for natural environment is one of the major causes of homesickness among rural out-migrants. As the main natural environment in cities, urban green space has been proven by numerous studies to have a positive effect on residents' mental health in various aspects, including reducing anxiety, relieving fatigue, and fostering perseverance. However, few studies have focused on the influence of urban green space on the mental health of the PAMs, especially on alleviating their homesickness syndrome. Using the data collected from interviews and questionnaire survey in the PAMs’ resettlement sites in Anshun, Guizhou, which has undertaken a heavy poverty alleviation task, this study examined the relationship between the physical activity, environment, function of urban green space, and the severity of PAMs’ homesickness, meanwhile paying attention to the impacts caused by different socio-demographic characteristics. The results show that urban green space is strongly associated with alleviating PAMs’ homesickness, and that all three factors play a positive role. Neighborhood green space is used the most, but suburban green space seems to provide better alleviation of homesickness. This study sheds lights on the critical role of urban green space for promoting PAMs' mental health, and aims to provide scientific reference to the planning and improvement for future migrant resettlements and urban green space.     

Uptake and use of biodiversity offsetting in urban planning – The case of Sweden

Globally, biodiversity offsetting is used to balance negative impacts on biodiversity and ecosystem services caused by exploitation. In Sweden, there is an increasing interest in biodiversity offsetting in urban planning. However, there is limited understanding about the use of the concept in a municipal context. This study aims to examine and critically reflect on the uptake and use of biodiversity offsetting at a strategic level in urban planning in Sweden. We study urban planning documents, and included Sweden’s 290 municipalities in the study. The result shows that more than 50% of Sweden’s municipalities mention biodiversity offsetting in their planning documents, targeting both regulatory offsetting of protected areas and voluntary offsetting of urban green space. The uptake is highest in urban areas experiencing high exploitation pressure, and many municipalities include both biodiversity and ecosystem services in their strategic work with offsetting. Most municipalities do not relate to the mitigation hierarchy (avoid, minimize, restore, offset), nor the goal of no net loss of biodiversity and ecosystem services. There is an ambiguity in the translation between losses and offsets, i.e. what type of offsetting (like-for-(un)like), what replacement ratios, and where to place the offsets. Few municipalities have developed processes, guidelines, strategic plans, etc., to integrate offsetting into the planning process. We conclude that the uptake of biodiversity offsetting is substantial, but with a fragmented, and often immature use in relation to ecological knowledge, and the planning process. We argue that, to develop biodiversity offsetting into an approach that delivers sound outcomes for nature and people in urban planning, municipalities must have a capacity in terms of organisational structures and resources.     

Natural forest expansion into suburban countryside: Gained ground for a green infrastructure?

Understanding patterns of natural forest expansion in rural regions under the influence of urbanization processes is crucial for integrated spatial planning across the urban-to-rural gradient. As a matter of fact, forest expansion is the only natural process that may counteract the consumption of the ecosystem capital and ecosystems services of rural lands due to uncontrolled urban sprawl. The paper addresses this topic in the paradigmatic case study of the countryside of Rome (Italy), characterized by counter dynamics of forest expansion and suburbanization. Morphological Spatial Pattern Analysis (MSPA) is applied to classify the forest landscape structure twice (1974 and 2008) according to seven categories (core, islet, perforation, edge, loop, bridge, branch) with different potential functional role as elements of a green infrastructure. Main findings are: (i) forest cover increased from 11% to 16% between 1974 and 2008; forest land uptake exceeds 4% of total study area, but shows a slower pace than the growth of built-up areas (10%); (ii) forest expansion has been to a large extent achieved by “sprawling” of islets (1.6% of the study area) along the stream network; (iii) more compact forest expansion has taken place on 0.2% of the study area in the form of additions to existing core areas or creation of new ones and (iv) the establishment of a network of protected areas nearby Rome has played a key role for the conservation and further expansion of core areas; yet, local loss of 1974 core areas stocks in a few protected areas indicates need of further law enforcement to ensure effective protection of the natural capital from degradation processes or even land conversion into built-up areas.Results calls for future in-depth investigations on the quality of newly created or maintained forest resource stocks associated to different spatial pattern structures. Integrated spatial planning strategies are outlined for the conservation of ecosystem capital and ecosystems services provided by forests, as major components of Rome's green infrastructure.     

The long-term prospects of citizens managing urban green space: From place making to place-keeping?

This paper discusses the long-term management or ‘place-keeping’ of urban green space by citizens and highlights enabling and constraining factors that play a crucial role in this continuity. While authorities have historically been in charge of managing public green spaces, there is an increased involvement of citizens in green space management. It is therefore relevant to study how citizens can contribute towards place-keeping and realize a continuity in managing and conserving the qualities of urban green spaces.We contribute to these debates by looking at three European cases characterized by long-term involvement of citizens in place-keeping. We conducted document analysis and interviewing of key informants to study green space management over time. Our analysis highlights what factors have contributed towards the continuity of this management, but also shows challenges and difficulties which citizens have experienced. Based on our fieldwork, we identify three factors of particular relevance for the continuity of place-keeping involving citizens.We found that long-term continuity is supported by a degree of formalization: established rules and procedures within groups provide stability to citizens. We also highlight the importance of adaptive capacity: citizens need to be able to adapt to contextual changes in order to cope with external political, socio-economic and cultural developments over time. The supporting role of authorities was also key in legitimizing and supporting place-keeping by citizens. Authorities can support place-keeping by citizens by providing security via stable policies, formally protecting the involved spaces, allowing long-term management contracts and contributing resources.     

Can canopy temperature acquired from an airborne level be a tree health indicator in an urban environment?

Nowadays, gathering information about tree health conditions in cities is necessary. Trees are essential in regulating urban microclimate and mitigating the urban heat island effect. Therefore, their health status should be crucial in urban vegetation monitoring. The growing number of new cameras, sensors and research methods allows for a broader application of thermal data in remote sensing vegetation studies. This research aimed to evaluate whether it is possible to use thermal infrared data to assess the health condition of selected species of deciduous trees in an urban environment. More specifically, the data must have a 3.6–4.9 µm spectral range, obtained during the day and the night. For this purpose, research was carried out in the city center of Warsaw (Poland) in 2020. During the airborne data acquisition, thermal data, laser scanning and RGB images were collected. Synchronously with airborne data, 617 ground references were obtained in different health condition classes (healthy, slightly poor condition, poor condition and dying) for five tree species: Acer platanoides, Acer pseudoplatanus, Aesculus hippocastanum, Tilia cordata and Tilia × euchlora. The results were as follows: (i) healthy trees were cooler than trees in poor condition and dying both during the daytime and nighttime; (ii) the difference in the canopy temperatures between healthy and dying trees was 1.06 °C of mean value on the nighttime data and 3.28 °C of mean value on the daytime data; (iii) all condition classes significantly differ from each other on daytime thermal data. The aerial thermal data can be considered a new alternative to hyperspectral data. Thermal sensing represents another method of assessing the health condition of trees in an urban environment – especially data obtained during the day, which can differentiate condition classes better than data obtained at night. The method based on thermal infrared and laser scanning data fusion could be a quick and efficient solution for identifying trees in poor health.     

Diversification of the urban forest—Can we afford to exclude exotic tree species?

Introduced tree species represent a substantial component of urban forests in cities all over the world. Yet there is controversy about the further use of introduced tree species. Many practice orientated publications,research papers and governmental websites in the fields of urban planning, urban forestry, and urban ecology argue for planting native species and avoiding introduced species. Such arguments for native-only species selection are also touted by environmental groups and the media. Consequently the debate has sometimes spiralled away from a sensible and rational platform where invasion risks and biodiversity loss are discussed, to a groundless and unreasonable argument where exotic species are generally considered incapable of providing ecosystem services. From a European perspective, we here aim to curate a set of necessary considerations for current and future discussions on native and non-native plant material in sustainable urban development. Using examples from Northern and Central Europe we illustrate that in some regions the catalogue of native tree species may be too limited to fulfil ecosystem services and resilience in harsh urban environments. A main message from our line of arguments is that we cannot afford to generally exclude non-native tree species from urban greening. If “native-only” approaches become incorporated in regional, national or international policy documents or legislation there is a risk that urban ecosystem resilience will be compromised, particularly in regions with extreme environmental conditions. Since both invasion risks and sizes of native species pools vary conspicuously at regional to continental scales we also argue to adapt urban policies on using non-native trees to regional contexts.     

A socio-ecological exploration of fear of crime in urban green spaces – A systematic review

Studies have pointed at the negative side of urban green spaces in terms of evoking fear of crime. However research on fear-provoking attributes suggests that there usually is no single attribute that influences fear but that rather a combination of attributes prevails. The aim of the paper is to systematically review those attributes that evoke fear of crime in urban green spaces and to highlight their complex interaction by adopting a social-ecological framework. Results include an overview of the reviewed literature with regard to authorship, journal, geographical distribution of the studies, types of urban green spaces studies, types of landscape stimulus used, applied methods, types of respondents involved and main study findings. Forty-eight studies met the authors’ inclusion criteria. The majority of the studies highlighted that individual factors (such as gender and past experience) were more influential than social and physical factors in evoking fear of crime. A proposed socio-ecological framework highlights the attributes which evoke fear of crime in urban green spaces and its interactions and can help guide future research.     

Too hot to handle? On the cooling capacity of urban green spaces in a Neotropical Mexican city

Urban areas are particularly vulnerable to climate change due to the Urban Heat Island (UHI) effect, which can be mitigated by urban vegetation through shading and evapotranspiration. Nevertheless, there is still a lack of spatially explicit information on the cooling capacity of green infrastructure for most Latin American cities. In this study, we employed Land Surface Temperature (LST) of the Neotropical Mexican city of Xalapa to (1) analyze its Surface UHI (SUHI) compared to its peri and extra-urban areas, (2) to assess the cooling capacity of urban green spaces larger than 1 ha, and (3) to evaluate the role of green spaces’ size, shape and their surrounding tree cover percentage (Tc) on green spaces cooling range. We evaluated the cooling range of green spaces and their relationships with green spaces metrics and Tc via a linear mixed-effect model and identified threshold values for the variables at 25 m, 50 m, 100 m, and 200 m from the borders of green spaces through Classification and Regression Trees. Xalapa exhibits a SUHI of 1.70 °C compared to its peri-urban area and 4.95 °C to the extra-urban area. Green spaces > 2 ha mitigated heat at ~2 °C and the cooling range was influenced by the size of green spaces ≥ 2.8 ha and Tc > 21% at 50 m and only by Tc surrounding the green spaces at 100 m and 200 m. This shows that the size threshold of urban green spaces should be complemented with the presence of Tc starting at least 50 m to maximize the cooling capacity provided by the green infrastructure. Planning agendas should account for the interaction between the size of green spaces and the cumulative cooling effect of scattered vegetation inside urban areas towards compact green cities to cope with urban warming.     

The pond network: can structural connectivity reflect on (amphibian) biodiversity patterns?

Landscape connectivity is a very recurrent theme in landscape ecology as it is considered pivotal for the long term conservation of any organism’s populations. Nevertheless, this complex concept is still surrounded by uncertainty and confusion, largely due to the separation between structural and functional connectivity. Amphibians are the most threatened vertebrates around the globe, in Europe mostly due to habitat alteration, and to their particular life cycle. Pond breeding amphibians are considered to be organised in metapopulations, enhancing the importance of landscape connectivity in this group of animals. We sampled the amphibian species present in two pond groups in Central Western Spain. We applied the graph theory framework to these two pond networks in order to determine the importance of each pond for the entire network connectivity. We related the pond importance for connectivity with the species richness present in each pond. We tested if connectivity (partially) determined the presence of the amphibian species sampled using logistic regression. The results show that the structural connectivity of the pond network impacts on the amphibian species richness pattern and that the importance of the pond for the connectivity of the network is an important factor for the presence of some species. Our results, hence, attest the importance of (structural) landscape connectivity determining the pattern of amphibian (functional) colonization in discrete ponds.     

Can pruning help maintain vitality of ash trees affected by ash dieback in urban landscapes?

Hymenoscyphus fraxineus causes a destructive invasive tree disease known as ash dieback threatening the survival of common ash not only in the forests, but also in urban and landscape settings. Pruning is a potential management practice that could help maintain tree vitality and aesthetics in parks, gardens, alleys and recreation areas, as well as maintaining veteran trees having high heritage or cultural value, or trees with high genetic importance (e.g. located in clonal seed orchards). In this study we investigated the maximum distance proximal to the lesion margin at which H. fraxineus can be detected on individual branches infected by the fungus in order to provide recommendations for pruning. Pruning of branches was carried out on 38 trees in southern Sweden. Tissue samples including bark and wood were collected from the margin of the lesion and at 5 cm intervals proximal to the lesion. Molecular analysis revealed presence of H. fraxineus in 91.3% of the investigated lesions. The proportion of lesions at which H. fraxineus could be detected declined with increasing distance from the lesion margin, with a significant reduction in the number of positive samples at 10 cm proximal to the margin. At 30 cm from the lesion edge the pathogen was never detected. Our results suggest that routine pruning may help maintain the vitality of younger trees. Pruning branches at least 35 cm from visible, active lesions in the bark should exclude the fungus and therefore reduce the probability of stem infection by H. fraxineus, however this cultural control tactic may only be economically feasible for high value amenity trees.     

Aspects influencing the selection of representative urbanization measures to quantify urban–rural gradients

The quantification of urban–rural gradients using urbanization measures has become standard practice in many urban ecological studies. Nonetheless, the choice of urbanization measures for a specific urban gradient still remains problematic. Increasing numbers of papers stress the importance of comparative urban ecological research, in an attempt to contribute to an understanding of the ecology ‘of’ cities. This implies that research in diverse urban areas globally should be comparable. This study follows an approach to quantify the urban–rural gradient in Klerksdorp previously followed in Melbourne, Australia with the goal to help elucidate the viability of creating a standard set of urbanization measures that is useful across continents. Satellite imagery and spatial analysis were used to calculate the values of 12 urbanization measures across a 900 km² landscape grid. Principal components analysis is commonly used to identify smaller subsets of measures to quantify urban–rural gradients. The results of this study indicate that factor analysis is more suitable than principal components analysis and ideal in identifying these independent measures of urbanization. The factor analysis revealed that landscape structure and demographic attributes are both essential characteristics of a city that needs to be accounted for in the choice of urbanization measures. Additionally, we identified seven aspects influencing the direct comparison of cities, namely: scale of analysis, spatial resolution, classification typology, accuracy of input data, specific measure equations, the type of statistical analysis and the habitat context. These aspects must be taken into consideration and resolved before effective comparative gradient research between cities can be achieved.