Urban trees provide multiple ecosystem services to city dwellers across the globe. However, their distribution differs greatly across and within cities, often reflecting contrasting environmental, socioeconomic, cultural and political characteristics, acting as an indicator of environmental inequality. We analyzed how the abundance, diversity and species composition of street trees in 51 Australian urban areas were related to socio-economic indices, such as income, education, age and immigration status. The effect of climatic conditions, including mean temperature of the warmest quarter (degrees C; Tmean), and aridity on urban tree distributions was also evaluated. Our results revealed that tree abundance was positively correlated with population density and negatively correlated with the proportion of residents born overseas; tree species richness was also negatively related with Aridity. Tree abundance varied across climatic gradients, with lower abundance observed in areas with high Tmean. Species composition was strongly related to both socio-economic and climatic variables. Our findings highlight important relationships between the abundance, richness and species composition of urban trees and socio-economic and climatic characteristics of urban areas across Australia. This study provides data-driven insights that can inform more equitable and climate-sensitive urban forestry planning and management.

Rapid urbanization threatens eco-environment quality (EEQ), in which the urban landscape pattern (ULP) plays a key role. However, the multi-scale mechanisms behind their spatial nonstationarity and nonlinear interactions remain underexplored. This study constructed an EEQ index, incorporating urban impervious surface and air pollution, based on urban ecosystem elements. Using a novel framework that integrates MGWR with a random forest model interpreted by SHAP, we explored the spatially nonstationary and nonlinear association between ULP and the EEQ index, and further quantified the contributions and thresholds of ULP both globally and locally. The results indicate that: (1) EEQ index in China’s coastal areas (CNCA) averaged 0.64, indicating a generally favorable level, with lower values in urban agglomeration distribution; (2) Urban built-up area percentage (UAP), urban built-up height (UBH), Shape, Contagion, and patch Euclidean Nearest-Neighbor Mean Distance index were the top contributors; (3) UAP and UBH have bidirectional effects on EEQ index in CNCA, reflecting characteristics of the Environmental Kuznets Curve. However, patterns were inconsistent for urban agglomerations within CNCA, indicating significant spatial discrepancies and nonlinear features, and growing inequality among urban agglomerations has heightened the complexity of their thresholds. Overall, prioritizing urban landscapes with order, strong cohesion, and effective connectivity in landscape planning can guide future urban expansion.

Urban forests are not merely green amenities; they support critical ecosystem functioning and services vital for healthy, resilient cities. Recognising urban forests as core infrastructure is essential to reversing the loss of mature trees, preserving biodiversity, and maintaining liveability amid increasing climate and environmental pressures. Although the benefits of urban forests for climate resilience, biodiversity, and public health are broadly acknowledged, policies to protect and enhance these vital ecosystems are often limited, underfunded, and inadequately enforced. As mature canopy loss today takes decades to be replaced (if ever), immediate and sustained investment is crucial to safeguard urban forests. This urgency reveals four interconnected gaps in current urban forest management and stewardship. First, urban forests require recognition, investment, and maintenance as essential infrastructure contributing to urban resilience, including biodiversity support, and to maximise the delivery of key ecosystem services such as cooling and carbon sequestration. Second, equitable access to greenspaces across all communities must be ensured to redress long-standing social and environmental injustices. Third, integrating urban forests into broader climate and biodiversity governance frameworks is critical to mainstreaming their management and protection. Lastly, resilience must be strengthened through evidence-based management practices responsive to evolving environmental changes and social contexts. These priorities must be complemented with strong legal protections, rigorous enforcement of legislation against illegal tree removal, and robust community engagement supported by integrated urban planning and improved monitoring. Without these, the ecological, social, and economic benefits provided by urban forests will remain threatened. By reframing urban forests as essential living infrastructure embedded in legal, financial, and planning frameworks, cities can become cooler, healthier, more biodiverse, and socially just. This framework offers timely guidance for policymakers to prioritise urban forests within climate resilience and sustainability strategies, securing benefits for current and future generations.

Urban trees provide vital ecosystem services in cities, including temperature regulation, air purification and climate adaptation. However, their growth is increasingly threatened by changing climate and air pollution. This study investigated the long-term effects of climate variability and air pollutants on radial growth of two commonly planted tropical tree species (Swietenia macrophylla and Samanea saman) in Sylhet City, a rapidly urbanizing area in northeastern Bangladesh. Using the dendrochronological approach, we developed tree-ring chronologies for both species and assessed correlations with precipitation, temperature, and air pollutants — particulate matter (PM₂.₅ and PM₁₀), Nitrogen oxide (NOₓ) and Ozone (O₃). Both species responded positively to monsoonal precipitation, highlighting the importance of seasonal water availability on tree growth. Conversely, the rising mean temperature significantly reduced radial growth in both species, particularly in April (S. macrophylla: r = -0.35, p = 0.02; S. saman: r = -0.33, p = 0.03) and June (S. macrophylla: r = -0.39, p = 0.01; S. saman: r = -0.42, p = 0.005). Among the pollutants, PM2.5 and O3 were associated with reduced growth in both species during February and January, respectively. These findings revealed that rising temperatures and high pollutant concentrations negatively influence tree growth in Sylhet City. Tree rings of both species can be used as a biomonitoring tool for tracking urban environmental change. Our study highlights the importance of climate-resilient and pollution-tolerant species selection to ensure sustainable urban forestry in tropical cities.

Climate niche approaches predict widespread vulnerability of urban tree species in cities, but the accuracy of these predictions has limitations given that many species can survive in cities outside their native distributions. Predictions based on functional traits offer an alternative approach, through quantifying species' physiological tolerances, to select stress-tolerant urban tree species for future climates. We aimed to investigate if climate niche-based approaches or functional traits can predict patterns of growth and survival for 61 urban tree species planted in common garden experiments in two Australian cities, Sydney and Melbourne. Climate niche was estimated using global occurrence records of tree species and mean and extreme rainfall and temperature variables. The species' thermal and precipitation safety margins were calculated as the difference between the species' climate niche limits and each city's climate. Functional traits related to drought tolerance, structural allocation, water use efficiency, stomatal anatomy, and conductance were measured for a subset of 18-26 species from both cities. Climate safety margins did not predict species' growth or mortality during the first two years after planting. Species from drier climates (mean annual precipitation of similar to 700 mm) had higher growth, while species from warmer/tropical climates (mean annual temperature >21 degrees C) exhibited higher mortality in both Sydney and Melbourne. High structural allocation (i.e., high leaf dry matter content) and higher water use efficiency (i.e., less negative leaf carbon stable isotope composition) were associated with low growth and mortality across species. Additionally, species with lower stomatal density and larger stomata had higher growth. Drought tolerance (i.e., more negative leaf water potential for turgor loss point) was linked to low mortality across species in both cities. Functional traits were better predictors of species' growth and survival than climate safety margins for newly planted urban trees.

Armed conflict accelerates soil and vegetation degradation, but field assessments and monitoring are often only possible at a later stage and/or indirectly, for example, through remote sensing data. We used the Dynamic World v1, a land-cover open-source dataset derived from Sentinel-2 imagery, to quantify land-cover change in Gaza (Palestinian territories) between September 2023 and September 2025. After cloud/shadow masking and 10 m spatial estimation, cropland and grassland declined from 5941 to 2056 ha (-65%), while bare soil expanded from 3918 to 17,663 ha (+351%). A comparator region in Israel showed modest changes (-4.5% and +3.4%, respectively), indicating that the Gaza trends are conflict-related rather than regional. High-resolution imagery reveals widespread transition from vegetated surfaces to debris fields and exposed soils. Our findings corroborate recent analyses based on commercial imagery while extending the assessment to 2025 through a fully open-source workflow. We present a fully reproducible workflow in Google Earth Engine to document and quantify land degradation using open Earth observation data under conditions of restricted ground access. These results provide a quantitative baseline for assessing soil and vegetation damage in conflict-affected areas.

Understanding tree species’ responses to climate change is essential for forest management. A key challenge is assessing species vulnerability and identifying those capable of persisting and thrive under future climates. Traditional correlative approaches using species distribution and climate envelopes to project climates where species currently occur but cannot distinguish physiological tolerances from dispersal limitations or biotic interactions. This study differs by quantifying climatic niches—the physiological tolerances of 313 North American tree species—using comprehensive worldwide occurrence datasets. Specifically, we: (1) identified Canadian regions with high climatic exposure; (2) determined species sensitivity based on climatic safety margins; and (3) identified candidates for assisted migration using climate analogues. Our results show that many species already exceed their thermal tolerance limits—45% for maximum temperature of the warmest month, and 100% for minimum temperature of the coldest month, reflecting range limits rather than immediate climatic stress. Although an average of 30 species may remain suitable under future climate scenarios, ‘no-analogue’ climates limit assisted migration potential across Canada. Moreover, species new to Canadian regions that become climatically suitable in the future currently face cold extremes as a climate bottleneck. Ultimately, only four to 13 species, depending on climate scenario and species niche, are projected to tolerate both baseline and future climates. These findings enhance understanding of forest resilience under climate change, directly informing vulnerability assessments and adaptive management strategies.

Stomatal conductance (gS) is a key driver of urban tree transpiration and heat mitigation potential, but few studies compare machine learning models for predicting gS across multiple species in cities. This study applies five machine learning models (XGBoost, Random Forest, Support Vector Machine [SVM], Neural Network, and Random Forest Adjusted) and two classical models (Multiple Linear Regression and Generalized Additive Model [GAM]) to predict gS for 15 dominant tree species in the urban forest of Mexico City using environmental variables (air temperature, vapor pressure deficit, photosynthetically active radiation, and leaf water potential). We trained the models on a dataset of 300 observations per species, with 70% for training, 20% for validation, and 10% for testing, and evaluated performance using RMSE, MAE, and R2. Overall, XGBoost, GAM and SVM consistently showed the highest predictive performance, with R2 values up to 0.997, while the Neural Network and Multiple Linear Regression performed poorly (R2 approximate to 0.10-0.65). Model performance varied substantially among species, with XGBoost performing best for seven species, GAM for four, and SVM for four. Our results demonstrate that tree species gS can be accurately predicted using machine learning models in urban forests; however, model choice should account for species differences in performance. We therefore recommend that practitioners consider ensemble approaches of multiple models, excluding only the Neural Network, when selecting predictors for individual species.

The energy-economy crop Sapindus mukorossi Gaertn. (S. mukorossi) has the potential to cope with energy transition while providing benefits such as saponin by Nature-based Solutions (NbS). However, its industrial development has long been limited by bottlenecks such as unstable raw material supply and compositional fluctuations. In this meta-analysis, we collected 2124 observation pairs from 43 publications in China to explore the effects of cultivation measures on S. mukorossi fruit yield, tree growth and leaf physiological characteristics. The results indicated that cultivation measures including fertilization, trimming, soil acidification, seed treatment and coercion had significant effects in promoting yield (51.0%), tree growth (14.89–31.0%) and leaf physiology (-29.9–19.0%) of S. mukorossi. Among measures, fertilization significantly contributing to fruit yield (95.0%) and aboveground biomass (81.0%) improvement by directly boosting nutrient supply and optimizing leaf phosphorus (19.0%) and potassium (14.9%) partitioning, while trimming enhanced photosynthetic capacity through light energy redistribution and growing canopy (67.7%), creating growth synergism with fertilization. In addition, elevation, climate, and soil properties modulated the effectiveness of cultivation measures through “energy-matter” coupling, with total nitrogen and temperature constituting the strongest promoter and suppressor, respectively, while soil total potassium dominated the response intensity through multiple modulation of increase and decrease effects. This study provides useful insights for the development of site-adapted management and efficient cultivation technology system of S. mukorossi plantation, which could support a nature-friendly model to empower the regional energy transition and the upgrading of the circular economy chain.

Urban areas face growing climate pressures from projected heat increases and rapid urbanisation, yet empirical studies assessing Indigenous population distributions relative to climate exposure and green infrastructure remain scarce. This study examines spatial associations between Aboriginal and Torres Strait Islander population sizes and urban environmental conditions across 614 urban areas in New South Wales, Australia, testing whether expected patterns of climate and green space marginalisation are evident. Using Generalised Additive Mixed Models, we quantified relationships with projected heat exposure (ΔMTWM), green cover percentage, green space accessibility, total population size, and socioeconomic advantage (Index of Relative Socio‑economic Advantage and Disadvantage, IRSAD), contrasting Aboriginal versus non‑Aboriginal population patterns using identical model parameters. Contrary to marginalisation expectations, Aboriginal populations showed positive non‑linear associations with higher ΔMTWM, greater green cover and larger total population size, and a positive linear relationship with IRSAD. Green cover significantly influenced Aboriginal, but not non‑Aboriginal, population distributions, while accessibility showed no significant associations for either group. Regional variation explained substantial additional variation in population distributions. These unexpected co‑location patterns challenge simple disadvantage narratives, revealing complex spatial dynamics potentially driven by historical settlement, contemporary planning or cultural preferences. These findings highlight the need for fine-scale, longitudinal and community research to inform urban climate adaptation planning. Our study emphasises the importance of considering local context and interacting factors when assessing climate change exposure and designing adaptation policies for Indigenous communities.

Urban vegetation, a key nature-based solution for mitigating heat stress, is critical as global warming, and urban heat islands amplify high temperatures in cities, affecting over half the global population. Yet, its potential warming effects remain unquantified globally, with mechanisms unclear. Using high-resolution satellite and climate data, we provide the first global assessment of vegetation's temperature regulation across 761 megacities across 105 countries, uncovering a paradox: cooling weakens in arid environments; and in 22% of cities with <1000-millimeter annual precipitation, vegetation, particularly grasslands and croplands, causes net warming. This results from lower albedo and reduced heat storage outweighing limited evapotranspiration in arid regions. During extreme heat, trees fail to cool 25% of cities, while grasslands and croplands fail in 71 and 82%, respectively, due to reduced evapotranspiration under high vapor pressure deficits and impeded canopy conductance. Climate-adaptive greening and irrigation are critical, while high-albedo surfaces may better mitigate heat in water-scarce cities. Misguided greening risks are worsening urban warming.

Urban forest planning, conservation, and governance often rely on data generated through positivist research paradigms, producing insights and decisions that are not easily accessible or meaningful to diverse publics. These gaps in understanding emerge across the spectrum of governance – from top-down institutional and political structures to grassroots, community-led practices of care. From a critical forest studies perspective, such tensions are not merely epistemic but also onto-political dilemmas, reflecting conflicting ways of being, knowing, and relating within multispecies urban landscapes. Adopting an EcoSocial work approach within an Indigenist Standpoint Pedagogical framework, this research explores how transdisciplinary, EcoSocial, and de/anti-colonial approaches can reframe urban forest governance as a process of co-creation rather than control. We draw on intersubjective and relational methodologies to surface alternative ways of learning, healing, and co-existing with urban forests. We consider the concept of becoming-intersectional in assemblage to describe the entangled relationships between humans and more-than-human beings, institutions and communities, science and art, settler-colonial systems and de/anti-colonial possibilities. Notions of individual and collective (shared) values in governance, settler colonialism, wilderness and the wild, decoloniality and care, healing, and ferality are considered in the context of our individual and collective belonging on this continent that is now known as Australia. This approach supports the development of collaborative approaches for diverse disciplines in environmental education. We reflect on the pedagogical potential of combining scientific datasets with arts-based storytelling to foster multispecies relationality and environmental education during times of climate, social, political, and economic upheaval. In doing so, this study contributes to an emerging practice of critical urban forest studies, one that foregrounds co-becoming, de/anti-colonial entanglements, and the transformative potential of cross-disciplinary collaboration in environmental education.

BACKGROUND:Plant species diversity is threatened worldwide, and urgent conservation action is needed. Emerging evidence demonstrates that urban forests, which are ubiquitous in cities globally, are repositories of threatened tree species diversity. Urban forests consist of billions of individual trees, suggesting that they may serve an important role as reservoirs of genetic diversity for ex situ tree species conservation. However, for most urban populations of tree species, little is known about their genetic diversity. How genetically diverse are urban tree populations? What proportion of a species' genetic diversity is captured in urban populations? How does genetic diversity of urban tree populations vary among species and cities? These questions remain relatively unexplored, undermining our understanding of the conservation value of urban forests and our ability to predict how these critical ecosystems will respond to climate change. SCOPE:This perspective explores the importance of genetic diversity in urban forests and reviews the current knowledge on this topic. We also discuss the potential role of urban forests in tree species conservation and propose utilizing urban forests as part of the broader ex situ collections to enhance conservation efforts. CONCLUSIONS:By considering urban forests as part of ex situ conservation collections, we can simultaneously advance conservation and urban forestry goals. Urban greening strategies that prioritize planting a genetically diverse assemblage of tree species can help overcome some of the major challenges to ex situ conservation such as limited planting space. At the same time, this strategy could increase urban forest resilience to disturbances such as pests, diseases, climate change or other stressors. This conservation strategy would build upon the important work done by botanic gardens while also engaging them with multiple stakeholders, including municipal urban foresters, nurseries, universities and the public.

Urban forests provide essential ecosystem services, including cooling, carbon sequestration, air purification, and support for human health that sustain cities worldwide. With ~70% of humanity projected to live in cities by 2050, these benefits are threatened by rising temperatures and shifting precipitation patterns stressing urban forests and reducing their functional performance. We assessed climate risks to 1,724 woody species across 387 North American and European cities. These urban forests, representing ~11.25 million inventoried trees and shrubs, currently store ~2.13 million metric tons of carbon and sequester ~146 thousand metric tons annually, while providing hydrological and air quality services valued at ~USD 14 billion per year. Using climatic safety margins and i-Tree Eco modelling, we project 61-82% of species exceed tolerance limits by 2050 (SSP3-7.0) across cities, driving 45% average declines across 15 ecosystem services. Some high-latitude cities face >90% losses. Warmer baseline climates, wetter warm seasons, northern latitudes, and lower tree density drive the greatest losses. Even slight exceedances create climate-service debt—gradual functional decline preceding severe failure—while large exceedances cause immediate service collapse. Our continental-scale translation of species risk to functional losses reveals severe urban forest vulnerability, closing critical gaps between climate exposure and ecosystem service outcomes. Immediate climate-adaptive planting is essential to sustain vital green infrastructure amid rapid urban expansion and warming.

Although tree cover reduces the urban heat island, no global estimate quantifies air temperature reductions by contemporary or future tree cover, currently and with climate change. Here, we estimate these reductions for all 8,919 large urban areas. Current urban tree cover mitigates 41-49% of the maximum potential air-temperature urban heat island that would occur in the absence of tree canopy. Tree canopy reduces summer air temperature by a population-weighted mean of 0.15 ± 0.03 °C, with wide variation (0.0-2.7 °C), benefiting 914 (805-1040, 95% CI) million people by >0.25 °C. Cooling benefits are greater in already cooler areas: high-income countries and suburbs. Current and plausible future tree cover mitigate only ~10% (6.7-18% and 6.3-17%, respectively) of the median mid-century climate-change warming under a moderate emission scenario. Our results suggest tree canopy expansion in densely settled low-income urban areas is necessary for equitable urban heat island mitigation and climate adaptation.

Urban forests are critical for climate adaptation and liveability, but effective irrigation management-key to their sustainability-remains poorly documented at the global scale. This study addresses this critical knowledge gap by analysing urban forest irrigation practices across 109 cities in 21 countries, offering one of the first global assessments of irrigation approaches, challenges, and opportunities. Using survey data, we examined water sources, irrigation frequency, constraints, and enabling conditions. Our results show that weather conditions were the leading factor influencing irrigation scheduling in 44 % of cities, while 56 % reported no formal water restrictions. Despite the importance of water conservation, 55 % of respondents reported having no water usage monitoring systems, and 73 % lacked financial incentives to promote water-efficient irrigation. A large majority (80 %) did not use recycled wastewater, and 58 % did not conduct water quality testing. Only 15 % of cities regularly used water-efficient irrigation technologies, and 47 % had no plans to implement smart systems. Over half (56 %) rated their current irrigation practices as only moderately successful. Budget constraints and infrastructure limitations were the most frequently reported challenges, followed by climate change-related concerns. While environmental variables such as mean annual temperature and irrigation need influenced specific practices, local governance and institutional actions had stronger effects. Cities in the Global South reported distinct strategies and constraints compared to those in the Global North. Our findings provide actionable insights for climate-resilient urban water strategies and underscore the need for targeted policies, capacity-building, and efficient technologies to enhance urban forest sustainability worldwide.