Aesthetic growth of a native tree species with desirable characteristics for urban green areas in arid and semiarid environments

Having an aesthetic form is one of the desirable aspects of trees used to create or reforest urban green areas, which is often achieved by procedures that require a great effort. The understanding of factors affecting the architecture of plants in natural conditions may be useful to promote a desirable shape during the growth process. Under the hypothesis that trees in high luminosity conditions have a more aesthetical growth, in this study we explore the relationship between plant shape and photosynthetically active radiation (PAR) in Bursera fagaroides, a characteristic species of the tropical dry forest and xerophytic shrub-lands useful for urban green areas in semiarid environments. To evaluate trees shape we calculate a symmetry index (I_S) by using two diameters of the crown, perpendicular to each other, and the total height. Measurements were made over three periods (before, during and after the growth period); and PAR was also measured for each tree. Linear regressions were used to analyze the relationship between the symmetry of trees and PAR received during the growth period. The post-growth symmetry of trees showed a positive relationship with the PAR received by trees during the growth period, suggesting that PAR effects can be harnessed to develop post-germination strategies for the production of trees with a more aesthetical growth in the studied species. Effect of PAR on the shape of plants may represent a practical option to promote aesthetical growth of trees and shrubs with importance for creation and restoration of urban green areas.     

Mapping the urban forest in detail: From LiDAR point clouds to 3D tree models

Trees are an integral component of the urban environment and important for human well-being, adaption measures to climate change and sustainable urban transformation. Understanding the small-scale impacts of urban trees and strategically managing the ecosystem services they provide requires high-resolution information on urban forest structure, which is still scarce. In contrast, there is an abundance of data portraying urban areas and an associated trend towards smart cities and digital twins as analysis platforms. A GIS workflow is presented in this paper that may close this data gap by classifying the urban forest from LiDAR point clouds, detecting and reconstructing individual crowns, and enabling a tree representation within semantic 3D city models. The workflow is designed to provide robust results for point clouds with a density of at least 4 pts/m² that are widely available. Evaluation was conducted by mapping the urban forest of Dresden (Germany) using a point cloud with 4 pts/m². An object-based data fusion approach is implemented for the classification of the urban forest. A classification accuracy of 95 % for different urban settings is achieved by combining LiDAR with multispectral imagery and a 3D building model. Individual trees are detected by local maxima filtering and crowns are segmented using marker-controlled watershed segmentation. Evaluation highlights the influences of both urban and forest structure on individual tree detection. Substantial differences in detection accuracies are evident between trees along streets (72 %) and structurally more complex tree stands in green areas (31 %), as well as dependencies on tree height and crown diameter. Furthermore, an approach for parameterized reconstruction of tree crowns is presented, which enables efficient and realistic city-wide modeling. The suitability of LiDAR to measure individual tree metrics is illustrated as well as a framework for modeling individual tree crowns via geometric primitives.     

Thermal Comfort Maps to estimate the impact of urban greening on the outdoor human comfort

Outdoor human comfort is an important factor in the evaluation of the liveability of a city as well as for promoting people’s health and well-being. In hot arid climates in particular, urban planning and design can considerably impact the day-to-day thermal comfort of the pedestrians, for better or for worse. Strategies to reduce thermal discomfort include shading structures, water bodies, and the promotion of natural ventilation – and most significantly, green areas. Trees have a major impact on the pedestrians in the built environment as they not only provide shading but also improve the microclimate in urban areas, thereby reducing the time during which discomfort is felt. The objective of this paper is to present a new methodology for dynamically quantifying the impact of different plants in urban areas on outdoor human comfort, through 3D urban energy modelling. The proposed methodology makes use of an urban energy modelling tool, providing a comprehensive view of the city energy fluxes, with a focus on the impact of trees on the human thermal comfort. Outdoor human comfort is assessed using the Index of Thermal Stress for the campus of the Swiss International Scientific School of Dubai (UAE), where “Thermal Comfort Maps” are designed to quantify the pedestrian thermal sensation and its variation in time and space. Additionally, the energy fluxes impinging on the urban pedestrians are quantified, dynamically, in hourly time step, providing an important instrument to understand their thermal stress, and the environmental factors affecting it. Based on the simulations, thanks to native greening, a significant improvement in outdoor comfort conditions was achieved in the campus, reducing the “warm/hot” and “very hot” thermal sensations from 1,291 h (on average over the entire campus) to less than 300 h by planting Ghaf and Acacia trees.     

Comparison of bird diversity between temperate floodplain forests and urban parks

Biodiversity in urban green areas has been widely explored in several bird studies because birds are known to be important bio-indicators. Many studies have investigated the different responses of bird communities to urbanization and land use changes in urban environments. However, there are still important knowledge gaps related to the impacts of the heterogeneity, spatial structure, and connectivity of green areas on avian diversity. Such information is needed for sustainable urban planning. In this study, we focused on the comparison of bird communities between urban parks in the heritage city of Olomouc and hardwood floodplain forests in the vicinity of the city. The results of the study indicate the high importance of urban parks for the maintenance of bird diversity even though urban parks are man-made habitats. The results highlight the importance of some native vegetation structures in urban parks (old trees, bush ecotones) for maintaining urban bird biodiversity. Some implications of the results can be widely used as a decision support tool for the management of urban green areas and for the planning of ecological networks in urban landscapes.     

Geospatial assessment of urban ecosystem disservices: An example of poisonous urban trees in Berlin,Germany

Urban trees play an important role in green infrastructure planning for the ecosystem services they provide. These services include carbon sequestration, the provision of clean air through oxygen production and filtering of airborne pollutants, and the offsetting of the urban heat island effect by providing shade and cooling. In addition to the well-studied positive effects of urban trees, under specific conditions, there are some unwanted side effects that need to be considered. Such negative side effects, such as allergies caused by tree pollen, traffic hazards from falling trees or tree parts or damage from roots or branches in resource supply or waste disposal infrastructures, are termed ecosystem disservices. An ecosystem disservice that is not very often illuminated in the urban context is the presence of poisonous urban trees. This paper provides a spatially explicit view of the distribution of poisonous urban trees in the city of Berlin, relating the spatial distribution of the hazard from this urban ecosystem disservice with the conditions under which it can have the most damaging effect by considering nearby playgrounds and areas with a high population density of children under 5 years old, the most vulnerable group within the urban population.     

Supplying urban ecosystem services through multifunctional green infrastructure in the United States

This paper summarizes a strategy for supplying ecosystem services in urban areas through a participatory planning process targeting multifunctional green infrastructure. We draw from the literature on landscape multifunctionality, which has primarily been applied to agricultural settings, and propose opportunities to develop urban green infrastructure that could contribute to the sustainable social and ecological health of the city. Thinking in terms of system resilience, strategies might focus on the potential for green infrastructure to allow for adaptation and even transformation in the face of future challenges such as climate change, food insecurity, and limited resources. Because planning for multiple functions can be difficult when many diverse stakeholders are involved, we explored decision support tools that could be applied to green infrastructure planning in the early stages, to engage the public and encourage action toward implementing a preferred solution. Several specific ecosystem services that could be relevant for evaluating current and future urban green spaces include: plant biodiversity, food production, microclimate control, soil infiltration, carbon sequestration, visual quality, recreation, and social capital. Integrating such ecosystem services into small-scale greening projects could allow for creativity and local empowerment that would inspire broader transformation of green infrastructure at the city level. Those cities committing to such an approach by supporting greening projects are likely to benefit in the long run through the value of ecosystem services for urban residents and the broader public.     

Allergenic pollen of ornamental plane trees in a Mediterranean environment and urban planning as a prevention tool

Green spaces and urban green infrastructure are new concepts in urban planning, and lately, the influence of green spaces in cities and how this presence affects local climate change have been taken into account. Moreover, some of the ornamental trees most used in cities provoke allergic symptoms in sensitized people. Due to the importance the plane trees in our parks and cities have as ornamental trees, this article assesses the urban Platanus airborne pollen concentration in the air of five cities of the SW Iberian Peninsula and tries to determine the differential factors that its distribution has by means of combining continuous monitoring of the air using volumetric spore traps and the geolocation of plane trees. They were counted separately according to the direction (Q1 NE, Q2 SE, Q3 SW, Q4 NW) around the spore trap location in circles of 100, 200, 300, 400, 500, 1000, 1500, 2000 and 2500 m in diameter. Pollen sums were distributed according to the predominant wind direction for each day. The highest concentrations for Platanus pollen were recorded in Don Benito. Differences amongst pollen stations were found and were mainly related to their degree of maturity and their proximity to spore traps, and finally, with the number of plane trees. Furthermore, other factors, as the pruning, which is different in each city and even in a more local way, affects pollination and is frequently unknown to aerobiological studies. The geolocation of ornamental trees can be a useful tool for providing summarized information about their behavioral differences amongst cities, which can be used to create healthy itineraries, minimizing the natural hazards in human health (allergic diseases) and could be implemented into a model to help policy-makers to create measures to improve green urban development.     

A walk on the wild side: Perceptions of roadside vegetation beyond trees

Urban nature is of vital importance for human well-being in an increasingly urbanized world. Despite the wide variety of urban greenspaces, previous research has mostly focussed on parks and in particular presence of trees. Although streets are fundamental urban structures and offer an array of green elements beyond trees, the perception and valuation of other kinds of roadside vegetation by urban residents is understudied so far. This study explores the range of roadside vegetation and associated ecosystem services perceived by city dwellers in densely populated inner city districts of two German cities. Further, we explored how wild-grown roadside vegetation is valued by interviewees. Results confirmed the important role of trees but also demonstrated that city dwellers perceive a variety of cultivated and “wild” green components other than trees. Respondents attached a wide range of meanings and values to roadside greenery and showed a surprisingly high awareness of associated ecosystem services. Wild urban roadside vegetation met with high approval, although planted and maintained vegetation was preferred. Our study illustrated that trees and other elements of roadside vegetation fulfil important functions in the view of the public. For many respondents, ecological and economical functions of roadside vegetation were more important than orderliness. This indicates opportunities for enhancing the biodiversity of urban streetscapes. As public green spaces are in short supply in many cities, enhancing cultivated and wild roadside vegetation could help to deliver ecosystem services in the areas near where people move and live.     

Effect of green infrastructures supported by adaptative solar shading systems on livability in open spaces

Lack of thermal comfort in the existing building stock in many warm summer climates and the COVID-19 pandemic have increased residents' temporary occupation of urban open spaces. However, climate change and other effects such as urban heat islands are also negatively affecting the livability of these spaces. Therefore, strategies are needed to improve the thermal conditions in these areas. In this context, the research designs, simulates and assesses an urban green infrastructure supported by an adaptative solar shading system. For this purpose, a public square to be renovated in Seville (Spain) is chosen. After an analysis of the current situation, more vegetation is added. However, trees are not planted fully grown, so their cover is not enough in the short term and an artificial system that protects from the sun by casting shade and that adapts to both their growth and the seasons is included. The urban space is characterized by on-site measurements, proposing four (initial, intermediates and final) scenarios using computational fluid dynamics simulations in an holistic microclimate modelling system. In turn, changes in thermal comfort are analyzed using the COMFA model. Results show that the air and surface temperature are decreased, reducing the number of hours in discomfort by 21% thanks to incorporating the green structure and by 30% due to the vegetation. It can be concluded that the use of these temporary urban prostheses enables urban spaces regenerated with vegetation to be enjoyed without waiting 20 or 30 years for the trees to mature, encouraging people to spend more time outdoors from the start of the intervention.     

城市行道树抗倒伏关键技术与措施

以沈阳市区行道树为研究对象，研究探讨城市绿地行道树移植后各种导致树木倒伏的因素，并针对行道树倒伏等相关问题，提供切实可行的抗倒伏关键技术，为城市行道树发挥景观生态效果提供技术支持。     

FlorTree: A unifying modelling framework for estimating the species-specific pollution removal by individual trees and shrubs

Atmospheric pollution is a threatening problem around the world, with tropospheric ozone (O₃), nitrogen dioxide (NO₂) and particulate matter (PM₁₀) among the most harmful pollutants for citizens’ health. Nature-based solutions such as urban trees can cut down air concentrations of these pollutants thanks to stomatal uptake and dry deposition on their canopies and, in addition, uptake carbon dioxide (CO₂) and store carbon in their tissues. Unfortunately, some species emit biogenic Volatile Organic Compounds (bVOCs) that are O₃-precursors leading to air quality deterioration. As a proper selection of species is essential for urban greening, we developed an innovative single-tree model (FlorTree) to estimate the maximum flux of air pollutants. FlorTree considered species-specific parameters, such as tree morphology (height and crown leaf area), leaf/shoot structure, leaf habit (deciduous/evergreen) and eco-physiological responses to environmental factors, for 221 urban tree and shrub species. We applied the FlorTree model to examine i) which are the best species for air pollution removal in the case study of Florence (Italy) and ii) whether the species-specific removal performance is affected by different climate and air pollution conditions in other cities, namely Bucharest (Romania) and Tokyo (Japan). Results suggested that 24 tall trees (mainly broadleaves belonging to Tilia, Acer and Fraxinus genus) may be recommended for Florence due to their large crowns at maturity (50 years old), relatively high stomatal conductance and no bVOCs release. These general characteristics, however, were affected by climatic and pollutant conditions, suggesting that FlorTree must be applied to the local conditions. Therefore, our results demonstrated that FlorTree can be applied in any city for maximizing the air quality improvement by urban trees.     

Green infrastructure inequality in the context of COVID-19: Taking parks and trails as examples

Urban green infrastructures play a critical role in enhancing the well-being of residents, yet their equitable access remains a concern, particularly during the COVID-19 outbreak. There is a lack of knowledge on how people respond to the pandemic regarding the usage of green infrastructure in cities. This paper explores the shifts in visitation to parks and trails, two popular types of green infrastructures in Salt Lake County, Utah, by analyzing the results of a survey conducted during the pandemic. Our conceptualization considers personal and neighborhood level factors, including personal socioeconomic status, existing inequalities of green infrastructures, urban form, and neighborhood conditions. People who reside close to the city center tend to go to parks more often, while those living in urban edges use trails more. Visiting green infrastructures less often is more likely in areas with higher COVID-19 infection rates. The regression results confirm the importance of neighborhood level factors and illustrate the intricate elements influencing people's decisions to visit different green infrastructures during the pandemic, which shows non-linear relationships. Wealthier, white, and younger people seem to enjoy green infrastructures more often, leading to the concern of amplified inequality. Higher COVID-19 cases result in higher demands for green infrastructures, which are not fulfilled during the pandemic, especially for vulnerable communities, leading to spatial exclusion. The findings highlight the importance of smart growth, including compact development, public transit, and pocket parks, in promoting the urban resilience of park and trail visits, as they may provide more opportunities for access and alternatives to green infrastructures even in the context of the pandemic.     

Quantifying green cover change for sustainable urban planning: A case of Kuala Lumpur,Malaysia

Despite the numerous benefits of urban green cover, urban land development has led to its destruction and degradation, including in Malaysia. In this study, time series Landsat satellite imagery were used to monitor green cover changes in Kuala Lumpur (KL), the largest and capital city of Malaysia. An advanced satellite image processing technique that considers the mixed-pixel problem was employed to determine the fraction of green cover in each Landsat pixel. Results show that the total green coverage in Kuala Lumpur decreased by 3% over the first study period, from 6564 ha in 2001–5,891 ha in 2013. However, it increased by 4% in the second, from 6215 ha in 2014–7,310 ha in 2016, and now green cover is 30% of the total land area of KL. These periods were selected to observe the changes in green cover before and after implementation of the “Greening KL” program, which was aimed to plant 100,000 trees in KL by year 2020. Most of the increase in green cover was contributed by trees planted along streets and in recreational parks. Other findings include a loss of ∼9% of green cover in two public parks compared to their total gazetted area, and a loss of green area in other forested parts of KL. Focus group discussions and structured interviews with public, private and non-governmental organizations indicate that green-cover losses can be partly attributed to weak regulations and their poor enforcement. Opportunities to protect and increase green cover in KL are also explored in this study. Such approaches are urgently needed before most of the green areas disappear from the landscape of KL, exacerbating the existing environmental problems in the city.     

Detecting,quantifying, and mapping urban trees' structural defects using infrared thermography: Implications for tree risk assessment and management

Urban trees are a fundamental and key component of urban green areas, however, they are subject to several stresses which can compromise their mechanical integrity through the development of defects such as wood decay. In this study, we evaluated the structural health state of trees in four urban parks in the city of Mytilene, Greece, using structural traits of the trees, their trunk surface temperature distribution as recorded using infrared thermography, and spatial statistics both at single tree and at park level. We developed thermal indices by analyzing data from 334 trees belonging to three main species (Robinia pseudoacacia, Morus alba and Melia azedarach). We estimated temperature spatial dependence across each tree trunk using Moran's I index, while statistically significant spatial clusters were assessed using local spatial autocorrelation statistics. Relationships between tree traits, thermal, and spatial indices were established using linear and logistic regression models. Finally, we used the Getis-Ord Gi* statistic for the identification of risky tree hotspots and we applied the kriging geostatistical procedure for mapping of such hotspots. Our results have shown that the thermal and spatial indices can sufficiently predict different types of structural defect, and to identify hotspots of risky trees and their spatial extent. This approach can successfully contribute to tree risk assessment for a more effective urban park management.     

Inequity in nature’s contributions to people in Ōtautahi/ Christchurch: A low-density post-earthquake city

Nature’s contributions to people (NCP) include the regulating, material, and non-material benefits of urban vegetation that improve well-being. It is increasingly important to plan cities that provide multiple types of NCP equitably to all residents of the city. However, due to historical legacies and planning policies, it is common for the most socially and economically vulnerable urban residents to suffer reduced access to the benefits of urban ecosystems. Previous studies of urban NCP have drawn attention to inequity in one or several types of NCP, but few have analysed a broad range. Here we analysed inequity in nine diverse forms of urban NCP across an index of economic and social vulnerability designed specifically to characterise vulnerability to environmental pressures. Furthermore, we used spatial analysis to map co-variance in vulnerability and a composite indicator of urban NCP, thus highlighting priority regions for future investments in green infrastructure. We applied this approach to the city of Christchurch/ Ōtautahi in Aotearoa/ New Zealand, which provides a valuable case study due to its multicultural population and recent history of widespread damage and regeneration following the 2011 earthquake. Overall, the distribution of urban NCP is inequitable to the disadvantage of more vulnerable residents. Residents of more vulnerable neighbourhoods experienced reduced provision of carbon stock, runoff retention, air quality enhancement, shade, educational green space, public outdoor space accessibility, private green space, and bird biodiversity contributions. Conversely, more vulnerable neighbourhoods had greater provision of erosion mitigation (although negligible in magnitude). The wide range of indicators used and assessed in response to vulnerability, coupled with an assessment of the type of vegetation cover (i.e. grass, tall trees) provides greater insights into how inequities in urban NCP can be addressed in future redevelopment.     

Visual structure of landscapes seen from built environment

Vegetation in cities keeps climate warming down and improves the health of people and ecosystems while making for a pleasant urban setting. Contemporary urban planning promotes sustainable green cities. Green and blue infrastructures, which help maintain an eco-friendly environment, are the primary instruments of this movement. This paper attempts to show the relative weight of plant life (trees, grass, orchards, etc.) seen from buildings in different urban settings (local urban patterns of high or low density of buildings). Landscapes open to view are identified by combining a digital elevation model and an 11-class land-use layer (including buildings, facilities, grey infrastructures, green and blue surfaces) in a computational tool that calculates viewsheds. The results show that vegetation is very much present in urban landscapes. In high-density built areas of city centres, the landscape is varied although not open and is dominated by trees, low-rise residential buildings and grass. Grey infrastructures and bushes are also very common. In low-density built areas the rank order of objects in view is similar but the landscape is more panoramic.     

“No place for wilderness”: Urban parks and the assembling of neoliberal urban environmental governance

For well over a decade, urban political ecology has been concerned with the neoliberalization of infrastructure as a key site of struggle in the reproduction of urban space. While urban forests, trees, and parks have not featured as prominently in that literature as other resources (e.g., water), they are increasingly managed and promoted as a form of “green” infrastructure by city governments eager to ally themselves with new environmentally-oriented framings of the modern city. Yet, the relationship between these new forms of green infrastructure and the neoliberalization of the city, in particular their ability to enable new ways of taking about the city and nature, and to constrain others, has been understudied. In this paper, I examine the ways in which urban parks are enrolled in political struggles to reorient the techniques of urban governance toward entrepreneurialism as the only viable model for economic development. Through a case study of Philadelphia's Fairmount Park System, I examine a series of events during the previous three decades in which Fairmount Park has become subject to this reorientation toward entrepreneurialism. Specifically, I examine how parks, no longer treated as spaces of “nature”, have been reframed as self-supporting constituents of a business-minded urbanism, promotional tools for the attraction of new labor to the city, and a reinforcement of the notion of entrepreneurialism as the inevitable urban development strategy for the 21st century. Yet, I also argue that these transformations are always in a process of negotiation. Even as parks become subject to these dominating discourses, new park construction is a site in which the conceptual assumptions that underpin neoliberal urban policy aren’t frictionlessly transferred from one instance to another but, even when successful, require significant work to overcome competing visions of urban nature.     

Supporting decision-makers in estimating irrigation demand for urban street trees

Greening cities is of considerable significance to creating sustainable cities. Cost-benefit analyses have shown that urban green is not only ecologically and socially desirable but also economically advantageous. However, maintaining this urban green is becoming challenging due to changing climatic conditions. With frequent heat-waves, droughts and increasing water scarcity in many regions, it is crucial to establish systematic approaches to economise the available water used for irrigation. Currently, cities rely on rough approximations to assess irrigation demand. To address this gap, a linear time series model was developed based on soil water balance and Water Use Classifications of Landscape Species approach. The model uses publicly available data regarding trees, soil, and current and forecasted weather to estimate the irrigation demand of urban street trees on a weekly time scale. The developed model is applied in a case study of a metropolis in a moderate continental climate. The results show more distributed irrigation demand than the currently implemented soil moisture based model of the case study city. Accordingly, the model can support the decision-makers to not only assess the irrigation demand of existing trees but also help in water budgeting of new plantation under varying climatic conditions.     

Implementing urban greening aid projects – The case of St. Petersburg, Russia

Recent years have seen the introduction of the concept of urban greening, defined as embracing the planning and management of all urban vegetation to create or add values to the local community. Green-space development has become recognised by international agencies and donors as important tool in improving the quality of urban livelihoods and urban environment. This paper evaluates an example of an urban greening aid project, carried out by Danish and Russian partners in the city of St. Petersburg, Russia. The project aimed to contribute to conservation and development of the cultural–historical, social and ecological values of St. Petersburg's urban green areas by implementing a structured, socially inclusive, well-informed planning and management approach. The project had three main components: (1) the development of a GIS-based information system to assist green-space planning and management; (2) on-site improvements in selected green areas and (3) awareness raising and public involvement activities. Ex post evaluation of the project showed that in spite of the limits of time and resources, important results were achieved. A more strategic approach to urban green-space planning and management, as promoted by urban greening, was adapted by some of the Russian project partners. Achievements also included notable physical improvements to one park. But the main project impacts were improved communication and collaboration between the local park department and local academia, as well as expertise developed in running a complex urban greening project. The project failed, however, in its public involvement ambitions.Moreover, the project should have facilitated discussion on some of the current premises of urban green-space planning and management in St. Petersburg, which insufficiently consider changing values and public preferences related to green spaces.     

Planning small for winning big: Small urban green space distribution patterns in an expanding city

While major urban areas are expanding, becoming more crowded, vegetated lands areshrinking. Built-up densification limits the planning of large urban green spaces,depriving urban dwellers of the benefits provided by such structures. In this context,small public urban green spaces (SPUGS) become of high value for urban landscapes,and their distribution throughout the city should aim to compensate the lack of largergreen areas. The driving forces of SPUGS distribution may be linked to the urbanfunctions they are usually paired with.The current study aimed to determine which are the urban functions that benefit ofhigher amounts of SPUGS in their proximities and to map the distribution and densityof SPUGS within Bucharest, helping us expose the green deprived communities.Results revealed that multi-dwelling residential areas are the ones with higher share ofSPUGS within walking distance. Nevertheless, analysis on SPUGS deprivation withinthe city showed that communist planned residential neighbourhoods are greener thanthe ones developed in the past three decades. Healthcare and commercial functionswithin the city recorded smaller shares of SPUGS in their proximity, highlighting thatvulnerable groups (such as ill people) are exposed to less vegetation, and that publicplanning documents are not encouraging developers to allocate more land for greenfeature development.These results are relevant for projecting the quality of outdoor environmentsthroughout Romania’s capital and for assessing potential future managementchallenges. The outcomes of this research provide local policy makers and plannerswith the vulnerable areas in which immediate action for expanding the greeninfrastructures should take place. At the same time, the methodological approachdescribed in the study proved to be efficient in assessing the distribution of SPUGSthroughout the city and the determinants of this distribution. It can be easily replicatedin other cities by scholars and planners.