Urban Greenery Research Articles

Towards SDG11: How Urban Greenery Can Help Us Build Sustainable Cities

In 2015, the United Nations launched 17 Sustainable Development Goals—efforts that should be taken to ensure the wellbeing of people and the planet by 2030. One of these goals aims to make cities sustainable by addressing environmental, social, and economic impacts to ensure cities are livable for future generations. This goal is important because more than half the world lives in cities now. Meeting the needs of many people in cities will not be easy, particularly with global problems like the hot temperatures experienced in cities, pollution, climate change, and food shortages. This is where urban greenery could help. Urban greenery includes the trees, parks, and other plants you see in cities. Greenery can help make our cities sustainable, providing benefits like cleaning the air, cooling the city in hot summer temperatures, and preventing flooding during heavy rains. Greener cities could make life better and healthier for everyone.

A GIS-Based Framework to Analyze the Behavior of Urban Greenery During Heatwaves Using Satellite Data

This work proposes a new unsupervised method to evaluate the behavior of urban green areas in the presence of heatwave scenarios by analyzing three indices extracted from satellite data: the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Moisture Index (NDMI), and Land Surface Temperature (LST). The aim of this research is to analyze the behavior of urban vegetation types during heatwaves through the analysis of these three indices. To evaluate how these indices characterize urban green areas during heatwaves, an unsupervised classification method of the three indices is proposed that uses the Elbow method to determine the optimal number of classes and the Jenks classification algorithm. Each class is assigned a Gaussian fuzzy set and the green urban areas are classified using zonal statistics operators. The membership degree of the corresponding fuzzy set is calculated to assess the reliability of the classification. Finally, for each type of greenery, the frequencies of types of green areas belonging to NDVI, NDMI, and LST classes are analyzed to evaluate their behavior during heatwaves. The framework was tested in an urban area consisting of the city of Naples (Italy). The results show that some types of greenery, such as deciduous forests and olive groves, are more efficient, in terms of health status and cooling effect, than other types of urban green areas during heatwaves; they are classified with NDVI and NDMI values of mainly High and Medium High, and maximum LST values of Medium Low. Conversely, uncultivated areas show critical behaviors during heatwaves; they are classified with maximum NDVI and NDMI values of Medium Low and maximum LST values of Medium High. The research results represent a support to urban planners and local municipalities in designing effective strategies and nature-based solutions to deal with heat waves in urban settlements.

Population health status and green urban areas: impact on health outcomes in two Italian regions

Abstract Background Living in urban areas has been linked to a rise in noncommunicable diseases. Nevertheless, there is scarcity of evidence emphasizing the combined impacts of certain urban attributes (e.g. pollution, excessive soil sealing, urban temperatures) and the existence of green spaces on health outcomes. Further studies are imperative to evaluate the association between chronic illnesses such as dementia and ischemic heart disease, and the presence of urban green areas. Methods We conducted an ecological study in two Italian regions. Prevalence of chronic diseases in Tuscany and Latium were obtained at the municipality level from public health databases available online and Normalized Difference Vegetation Index (NDVI) was calculated for 2023. Descriptive analyses and Poisson regression models were run to assess the association between green space and chronic diseases prevalence, adjusting for age, sex, education, employment, foreign residents, income, urbanicity and spatial correlation. Results Preliminary analyses were conducted on 273 municipalities in Tuscany. Mean prevalence per 1000 inhabitants of dementia and ischemic heart disease were 15.75 (SD = 5.3) and 48.25 (SD = 11.06), respectively. Mean NDVI across municipalities was 0.37 (SD = 0.04). Higher green exposure is associated with lower prevalence of ischemic heart disease (β= -0.21; p < 0.05) and dementia (β=-0.3, p < 0.05). Analyses will be executed for the Latium region and complete results will be available by mid-June. Conclusions The presence of urban greenery appears to be associated with a reduction in chronic illnesses. While further studies are warranted, it is crucial to adopt urban policies focused on green spaces and citizens’ health outcomes. Generating evidence for decision-makers is essential for shaping urban environments in ways that promote both health and overall human wellbeing. Key messages • Living in green urban areas appears to positively impact human health, reducing chronic disease prevalence. • Greenery serve as a tool for mitigating and adapting to the climate crisis, promoting health.

Deep learning modeling to assess surface temperature and greenery impact on emergency room access

Abstract The escalating land surface temperature is a key environmental indicator with potential repercussions on human health. An artificial NN model was built to predict the number of ER accesses as a dependent variable, to establish the predictive power and interactions of land surface temperature and normalized differential vegetation index(NDVI), which is used to measure urban greenery.A map of Taranto was built by vector files on the Apulia region website and processed using R Studio 2023.06.2.The vector file containing the mapping of the city of Taranto was processed to obtain a 200mx200m grid of the entire surface.The Local Health Authority of Taranto provided indications of the residences of ER accesses, and coordinates were merged to gridded vector file to obtain the average of ER accesses and the socio demographic features per single grid unit. NDVI and surface temperature were averaged for July 2023 using images from Landsat 8(30m) and merged to the vector providing an average value of temperature and NDVI index per single quadrant. The dataset was divided into two db according to an 80/20 ratio respectively for the training and test dataset.A NN model was built on dichotomous value (above/below median) for each quadrant (6513 units) with hyperparameter tuning technique using the accuracy to select the best model.A MOC model was built to reduce the probability of NN detection by at least 40% in a randomly selected subject.A MOC model was built considering sociodemographic variables as fixed features and an epsilon of 0 for 175 generations and an ICE curves population initialization strategy. NNET accuracy value was 0.849 and 0.841 in training and testing, suggesting a good fitting of the model.Relative change plots were adopted to show the amount and the direction of generated counterfactuals, to reduce grid unit prediction to be over median.LST decreasing and NDVI score increasing were associated with a reduction of classification probability of grid unit. Key messages • Rising land surface temperature is a critical environmental indicator with potential impacts on human health. • Artificial neural network models perform well in predicting the number of ER accesses with respect to land surface temperature and NDVI, which is used to measure urban greenery.

Creating and sustaining urban green spaces in Africa under phenomenal urbanisation: residents’ perspectives on home gardens in Wa, Ghana

Attaining the goals of the New Urban Agenda and Sustainable Development Goal (SDG) 11, which aims for sustainable, inclusive, and resilient cities, necessitates accelerated efforts to green urban environments. While keeping home gardens is not new, it offers a unique potential as a deliberate strategy for urban greening in Africa. However, Ghana has limited empirical evidence regarding the motivations, challenges, and constraints of keeping domestic gardens, which is essential for informing urban greenery policy. This study addresses this knowledge gap by employing the self-determination theory and conducting an exploratory cross-sectional survey with 285 structured questionnaires administered to residents in seven rapidly growing neighbourhoods in Wa, Ghana. The results reveal that 56% of respondents had gardens within their properties, with beautification (56.1%) and food production (52.3%) being the primary motivations. Vegetables (46.7%) and trees (30.2%) were the most commonly cultivated plants. Conversely, limited space (49%) and busy schedules (34%) were identified as the main barriers to home gardening. The findings indicate that the motivation for owning gardens aligns with the autonomy need of the self-determination theory. In contrast, the relationship need, which correlates with environmental motivations, was notably low among residents. The study recommends that local authorities, civil society organisations, and neighbourhood planning committees implement aggressive sensitisation and education campaigns to promote the environmental benefits of domestic gardening.

Quantifying the potential of evidence-based planting-pattern for reducing the outdoor thermal stress from a bio-meteorological perspective in tropical conditions of Indian cities.

The impact of declined natural greenery and increased built surfaces exacerbates heat stress in urban areas causing limited usage of outdoor spaces. Greenery strategies such as trees are capable of mitigating outdoor thermal stress gain because of their phytological properties. While urban greenery guidelines have suggested the ad-hoc procedure of tree planting-schemes based on aesthetic-value, soil-water preservation etc., understanding of their morphological character help in regulating extreme thermal condition. Hence, this study aims to investigate the most efficient planting pattern based on canopies densities and trees clusters for reducing the outdoor thermal stress from bio-meteorological perspective.It initiates with the measurement of the site's morphological and meteorological attributes in existing commercial market of Bhopal City which has a humid sub-tropical climate (Aw, Koppen climate categorization). Furthermore, it leads to the development of 4-different iterated clusters incorporating moderate to high-density canopies and their overlaps pattern to estimate reduction potential in outdoors using field surveys and validated simulation model. The reduction potential in terms of magnitude and duration of thermal stress is quantified across 3-thermal variables i.e., air temperature, mean radiant temperature and universal thermal climate index. Results indicate highly-dense canopies are more effective in reducing greater magnitude of thermal stress along longer duration. Also overlapped planting pattern within the same canopy density does not make significant difference in stress reduction as compared to the changing the densities. This study will help planners and landscape architects to adopt evidence-based planting-pattern strategies for improving outdoor microclimate.

Evaluating the tradeoffs between water conservation, aesthetic value, evaporative cooling and CO2 emissions in St. augustinegrass and buffalograss

Urban lawns comprise a significant portion of urban greenery and provide several ecosystem services. Nevertheless, maintaining lawns comes with significant water costs in semi-arid inland southern California, as they require consistent irrigation to stay healthy and productive. The main objective of this study was to evaluate the effect of a wide range of irrigation rates and frequencies applied autonomously by a smart ET-based controller on the aesthetic value, cooling potential, and CO2 efflux of two warm-season turfgrass species. For three years, we studied the responses of Buffalograss and St. Augustinegrass to six irrigation rates and two irrigation frequencies in Riverside, California. Under historical average climate conditions, the minimum irrigation rate for Buffalograss was 93 % ETo, and for St. Augustinegrass, it was 74 % ETo. Under projected future climate conditions, the estimated minimum irrigation rate for Buffalograss did not change, but for St. Augustinegrass, it increased by 4 % and 7 % in 2100 under low emission (RCP 4.5) and high emission (RCP 8.5) scenarios, respectively. On average, canopy minus air temperature in Buffalograss was 6.2 ℃, and in St. Augustinegrass, it was 1.1 ℃. The average CO2 efflux in Buffalograss was 122.3 µg CO2-C m−2 s−1, and in St. Augustinegrass, it was 182.8 µg CO2-C m−2 s−1. Our results showed that turfgrass aesthetic values, cooling potential, and CO2 efflux diminished as the irrigation rate decreased, but at different rates for each turfgrass species.

The Use of Socio-Environmental Indicators to Assess the Needs Relating to the Development of Urban Greenery

The Use of Socio-Environmental Indicators to Assess the Needs Relating to the Development of Urban Greenery

Exploring the interplay of urban form and greenery in residents’ affective and cognitive responses

Stress is a prevalent issue in modern cities, exacerbated by urban development and significantly affecting urban dwellers. While it is known that greenery can contribute to people’s wellbeing, it is unclear if it can mitigate the negative effects of urban development. In this study, we aim to explore the intricate dynamics between urban form and greenery to dissect their collective effect on human wellbeing, operationalized through physiological relaxation, preference, and emotional responses. The study employs an experimental study design using virtual reality technology to immerse participants (n=156) into residential neighborhood scenes, and measures affective and cognitive responses using skin conductance measures and a survey, respectively. In general, the findings confirm the critical role of urban greenery on affective and cognitive responses. Interestingly, we observe that this effect is highly dependent on the context and shows diverging patterns between different neighborhood types. In particular, in certain neighborhoods (popular, 60 s, and cooperative), greenery, no matter if species-poor or biodiverse, consistently improves preference and physiological relaxation. In contrast, urban centers and single-family residential areas may accommodate more biodiverse green spaces without compromising their existing high preference levels when compared to less affluent neighborhoods. The study concludes with a call for urban planning to cultivate equitable, green, and distinctively designed urban environments. This shift underscores the critical role of innovative urban design in improving the wellbeing of urban dwellers.

Evaluating the cooling performance of vegetation combined with a fountain in horizontal and vertical urban environments

Urban greenery and fountains effectively mitigate the urban heat island (UHI) effect. While many studies have assessed individual vegetation configurations (grass, shrub, and tree) and fountains at pedestrian heights, few have explored their combined effects horizontally and vertically. This study uses the ENVI-met model to evaluate the cooling effects of three vegetation configurations and their combinations with fountains in a typical historical and cultural neighborhood. The “grass, shrub, tree and fountain” scenario achieved the most substantial cooling, reducing air temperature (Ta) by 5.61 °C and mean radiant temperature (Tmrt) by 17.39 °C. Adding shrubs to the existing trees had minimal impact on Ta and Tmrt. Incorporating fountains into various vegetation configurations scenarios further lowered Ta by 3.58°C-3.66 °C and Tmrt by 2.97°C-3.27 °C. Trees primarily improved Tmrt through shading, while fountains were more effective at reduce Ta. This study offers theoretical and scientific guidance for optimizing urban street microclimate design from horizontal and vertical perspectives.

Intersecting impacts: urban noise pollution on sleep quality and mental health outcomes

This study probes the intricate dynamics between urban noise pollution, sleep quality, and mental health, centering on Generation Z-those in their formative years and early adulthood. It aims to illuminate the particular impacts of environmental noise on the well-being of these younger urban dwellers. Through a multidisciplinary lens, the research assesses how persistent urban noise exposure perturbs sleep-a critical factor in psychological health-and fosters stress, anxiety, and depression in this demographic. By integrating objective acoustical measurements with Gen Z's subjective health reports, the methodology quantifies urban noise's influence on sleep and its ripple effects on mental health. Additionally, it evaluates noise mitigation strategies like soundproofing and urban greenery, for their potential to mitigate these adverse outcomes. Mapping the nexus between environmental noise, sleep disturbance, and mental health concerns among Generation Z, the study seeks to enrich understanding and guide interventions for improved urban habitats, better sleep, and enhanced mental well-being, addressing a significant public health issue.

TEN QUESTIONS CONCERNING THE ROLE OF URBAN GREENERY IN SHAPING THE FUTURE OF URBAN AREAS

Strengthening sustainability starts with maintaining a balanced relationship between society, the environment, and the economy, and one of the pillars of doing this is increasing the amount of green infrastructure and expanding it in urban areas. Densely populated urban areas with fewer greenery are particularly vulnerable to the effects of climate change, including sea level rise, storm surge, heat waves, droughts, and changing diseases, and vulnerable populations in urban areas are likely to be disproportionately affected. In addition to providing multidimensional benefits to all ecosystems, urban greenery is influential in developing sustainable lifestyles and healthy eating habits, increasing individual well-being derived from the need for a sense of belonging and social inclusion, as well as reducing carbon footprint. As urban greenery is part of urban development but less attention is paid to it, the benefits of these areas should be further explored and highlighted. Thus, ten questions were raised concerning the contribution of urban greenery to the future of urban areas. The questions not only to address important issues related to urban greenery and to provide guidance for future studies, but also to offer new perspectives for future policies. The answers to the ten questions are based on the expertise of the authors to highlight the importance and the potential of urban greenery in shaping the future.

Urban greenery distribution and its link to social vulnerability

Urban greenery plays a pivotal role in urban environments, impacting the environmental well-being and people’s comfort. Several studies have demonstrated a strong link between urban greenery and socioeconomic status but still lack an analysis of greenery on uneven distribution in social vulnerability. This study assesses how multi-level greenery rates distribute and associate the social vulnerability of people in 429 census tracts in the Seattle metropolitan area. It integrates multi-source urban informatics data, including remote sensing data and street view imagery, to identify various vegetation types. Then, it uses the interpretable machine learning model to explore the relationship between street-level green space distribution and community vulnerability. The results show a serious problem of uneven distribution of green spaces in urban centers since urban areas are built up and fragmented the landscape. Areas with low urban greening in the Seattle area have higher rates of poverty, unemployment, racial segregation, and housing overcrowding. Besides, greening features like street green views, which are more related to human perception, have a great association with social vulnerability. These findings contribute to the urban green spaces to better promote community equity and vulnerability.

Urban Perception Evaluation and Street Refinement Governance Supported by Street View Visual Elements Analysis

As street imagery and big data techniques evolve, opportunities for refined urban governance emerge. This study delves into effective methods for urban perception evaluation and street refinement governance by using street view data and deep learning. Employing DeepLabV3+ and VGGNet models, we analyzed street view images from Nanshan District, Shenzhen, identifying critical factors that shape residents’ spatial perceptions, such as urban greenery, road quality, and infrastructure. The findings indicate that robust vegetation, well-maintained roads, and well-designed buildings significantly enhance positive perceptions, whereas detractors like fences reduce quality. Furthermore, Moran’s I statistical analysis and multi-scale geographically weighted regression (MGWR) models highlight spatial heterogeneity and the clustering of perceptions, underscoring the need for location-specific planning. The study also points out that complex street networks in accessible areas enhance living convenience and environmental satisfaction. This research shows that integrating street view data with deep learning provides valuable tools for urban planners and policymakers, aiding in the development of more precise and effective urban governance strategies to foster more livable, resilient, and responsive urban environments.

Investigating the efficacy of a fast urban climate model for spatial planning of green and blue spaces for heat mitigation

Problems caused by urban heat have prompted the exploration of urban greenery and blue spaces for heat mitigation. Various numerical models can simulate heat-related processes, but their use as support-tools to urban planners remains underexplored, particularly at the city-scale, due to high computational demand and complexity of such models. This study investigates the spatial relationships between urban heat, urban form and urban green and blue spaces with the fast climate model TARGET (The Air-temperature Response to Green/blue-infrastructure Evaluation Tool), which only requires minimal inputs of standard meteorological data, land cover and building geometry data. Using the City of Zurich as our case study, we: (i) validated the TARGET model against air temperature measurements from private sensor networks, (ii) performed a sensitivity analysis to identify key variables affecting urban heat, and (iii) investigated urban heat relationships with blue-green cover at locations frequented by pedestrians. Presence of urban green and blue spaces across the region shows potential for reducing local air temperatures by up to 5.2 °C (with urban forest). Investigating this relationship at different locations in the city revealed key districts that should potentially be targeted for reduction of pedestrian heat-impacts, due to their high pedestrian traffic, fewer green and blue spaces and high daytime air temperatures. Our results not only provide insights into the cooling effect of different amounts of green and blue features in the urban environment, but also demonstrates the application and integration potential of simplified models like TARGET to support the planning of more liveable future cities.

Surface and canopy urban heat island disparities across 2064 urban clusters in China

The vast majority of urban heat island (UHI) studies are now derived from surface temperatures, substituting for the original air temperature-based definition. The disparities in hourly surface-canopy UHI effects (SUHI, CUHI) and the contrasting mechanisms are currently poorly understood. Here, we use high-resolution hourly LST and air temperature data from 2064 urban clusters in China to estimate SUHI and CUHI intensities and their driving mechanisms during the summer and winter of 2022. Across all urban clusters, we find that SUHI is on average ten times higher than the CUHI in the summer (0.97 VS. 0.09 °C) yet nearly triple that in the winter (0.30 VS. 0.11 °C), with SUHI exceeding CUHI in 91.5 % and 65.7 % of urban clusters, respectively. Seasonal and hourly analyses on SUHI/CUHI confirm typically opposite hysteresis variations (magnitude, peak, and timing of occurrence) and more correlated surface-canopy UHIs patterns during the night. We further demonstrate that SUHI magnitude can be largely explained by biophysical factors, urban attributes, and climate contexts, whereas CUHI interferes with additional constraints linked to ground-air energy transfer and advective dissipation. The improvement of urban greenery aids summer cooling efficiently in equatorial and boreal regions, while albedo measures are relevant in mitigating nocturnal warming in arid regions. Our findings support multiple technologies as ideas for urban three-dimensional UHIs (surface, canopy and boundary) and energy mechanisms, and the urgent need for ambitious urban heat mitigation strategies to minimize future climate change impacts.

The effect of industrial and urban dust pollution on the ecophysiology and leaf element concentration of Tilia cordata Mill.

The influences of airborne trace elements in urban dust on element concentrations and functional traits of Tilia cordata were examined. For the present study, the unwashed and washed leaves of T. cordata were collected to assess the concentration of metals in Katowice City, Poland, from sites of different traffic intensity and industry activity. The content of Al, Cd, Cr, Cu, Fe, Mn, Pb, Zn, C, and N was measured. Additionally, a number of functional traits such as photosynthetic pigment content, specific leaf area (SLA), leaf dry matter content (LDMC), and diseased areas of the leaves were determined to assess the impact of the polluters on the physiology of the trees and their resources acquisition strategy. We hypothesized that the photosynthetic pigments of T. cordata will decrease with the traffic and industry intensity, and the traits related to the resources acquisition and stress resistance will shift into a more conservative strategy.The Principal Component Analysis and the Inverse Distance Weighting (IDW) interpolation method helped to identify that the Fe, Zn, Al, and Cr were related mainly to traffic intensification and Pb to industrial activities. The results indicate that Katowice is considerably polluted by Zn (up to 189.6 and 260.2mgkg-1 in washed and unwashed leaves, respectively), Pb (up to 51.7 and 133.6mgkg-1), and Cd (up to 2.27 and 2.43mgkg-1) compared to other cities worldwide. Also, a reduction of approximately 27% in the photosynthetic pigments was observed at the high-traffic and industrial sites. The trees from the mainly affected areas with heavy traffic and industry tend to apply a conservative resources strategy with a decrement in SLA and an increment in LDMC. In contrast, the opposite trend was observed at the less affected sites (high SLA, low LDMC). The study showed that unfavourable urban conditions can trigger a plastic response on multiple levels. Knowledge of the possible paths of adaptation to urban conditions of different plant species is nowadays crucial to appropriate urban greenery planning.

Well-planned greenery improves air urban quality - Modelling the effect of altered airflow and pollutant deposition

Urban air quality is influenced by vegetation through alterations in airflow and pollutant deposition processes. We investigated these interactions by integrating the Vegetation Impact Dynamic Assessment model (VIDA) with the Large-Eddy Simulation model PALM. Our analysis focus on nitrogen dioxide (NO₂) and particulate matter (PM) concentrations at the local scale, considering three tree genera. Our findings reveal the necessity of accounting for both gaseous pollutants and particles separately due to their differing mechanisms of deposition onto leaves. The coupled PALM-VIDA model demonstrates a significant reduction in PM levels across the modelling domain and within street canyons when deposition to vegetation is incorporated. Reduction in NO₂ through deposition to vegetation is lower but human NO2 exposure can still be decreased if tree species selection and placement leads to desirable effects on air flow. Sparse tree arrangements or species with sparse crowns facilitate ventilation and are often better at reducing NO₂ concentrations in street canyons compared to denser vegetation with higher deposition but negative effects on ventilation. Our study informs urban planning and green infrastructure design, underscoring the multifaceted role of urban greenery in air pollution mitigation strategies. Its main conclusion is that both deposition processes and the influence of air mixing and ventilation need to be considered to accurately assess the effects of urban trees on local air quality. Ill-considered placement and species selection may cause a net increase in pollutants underneath the trees. However, careful planning can address this risk and instead improve overall air quality.

Green spaces provide substantial but unequal urban cooling globally

Climate warming disproportionately impacts countries in the Global South by increasing extreme heat exposure. However, geographic disparities in adaptation capacity are unclear. Here, we assess global inequality in green spaces, which urban residents critically rely on to mitigate outdoor heat stress. We use remote sensing data to quantify daytime cooling by urban greenery in the warm seasons across the ~500 largest cities globally. We show a striking contrast, with Global South cities having ~70% of the cooling capacity of cities in the Global North (2.5 ± 1.0 °C vs. 3.6 ± 1.7 °C). A similar gap occurs for the cooling adaptation benefits received by an average resident in these cities (2.2 ± 0.9 °C vs. 3.4 ± 1.7 °C). This cooling adaptation inequality is due to discrepancies in green space quantity and quality between cities in the Global North and South, shaped by socioeconomic and natural factors. Our analyses further suggest a vast potential for enhancing cooling adaptation while reducing global inequality.

Prospects and limitations of soil amendment and irrigation techniques for the water-saving public urban greenery and ephemeral weed management in the sandy soils of the United Arab Emirates

Prospects and limitations of soil amendment and irrigation techniques for the water-saving public urban greenery and ephemeral weed management in the sandy soils of the United Arab Emirates