Fear of crime in public spaces is a major policy problem worldwide. Environmental Crime Prevention proposes that modifying the built environment can reduce the fear of crime, but key questions remain: are these interventions equally effective across genders, and what intensity maximizes safety perceptions while optimizing costs? Here we evaluated three interventions: ‘Eyes on the Street’ (adding windows to blind walls), neutral stimuli (removing graffiti by repainting walls) and ‘Nature-Based Solutions’ (integrating tidy vegetation into urban infrastructure) in the context of ‘Broken Windows’ disorder. Interventions were applied at varying intensities across four types of public spaces. Using a randomized experiment in Chile with photo simulations and an adapted Positive and Negative Affective Schedule, we collected 18,150 perception ratings from 2,028 respondents. The results show that perceived safety improvements are positive but nonlinear, indicating diminishing returns beyond a certain intervention intensity. Critically, responses were highly gender specific: interventions were more effective for men, suggesting that environmental changes alone do not fully address women’s perceived insecurity. Crime is a continuing urban challenge. This study, based in Chile, finds that design interventions are effective but less so as new ones are added and that interventions are more effective at reducing the fear of crime in men than women.
Living-condition deficits remain widespread in rapidly growing cities, yet their spatial distribution is poorly measured beyond metropolitan areas, limiting progress toward Sustainable Development Goal (SDG) 11.1 on adequate, safe and affordable housing. Here we conceptualize morphological deprivation as an area-based form of disadvantage reflected in built form, residential density, road connectivity and infrastructure conditions, and generate globally comparable, neighborhood-scale estimates across 5,132 cities in Africa, Asia, and Latin America and the Caribbean. Using harmonized geospatial datasets and supervised learning trained on eight benchmark cities, we estimate that 395 million people (20.2% of the covered urban population) live in morphologically deprived neighborhoods. While relative prevalence is highest in Africa (43.6%), substantial populations are affected across all regions. Notably, over one-third (136 million) reside in small and medium-sized cities, revealing a large but underrecognized burden and underscoring the need to prioritize these cities in data, finance and policy efforts to achieve SDG 11.1. This study provides neighborhood-scale mapping of populations living in infrastructurally and environmentally constrained urban areas, identified from the physical form of the built environment, across 5,132 cities in Africa, Asia, and Latin America and the Caribbean. It reveals that over one-third of this burden falls on small and medium-sized cities, highlighting a substantial yet overlooked obstacle to achieving SDG 11.1.
During urban stressors such as floods, rising information demands spur citizen-created tools that partly meet data needs but engender information scattering — the dispersion of situational-awareness data across multiple platforms — that undermines community safety. We examine this challenge and pose strategies to overcome it in the future.
Natural gas consumption in Chinese cities has nearly tripled over the past decade, improving air quality but leaving its climate impacts uncertain due to poorly quantified supply-chain leakage. Here we quantify methane emissions from natural gas consumption in the Yangtze River Delta metropolitan cluster using a decade (2012–2021) of atmospheric ethane (C2H6) observations, a tracer unique to fossil fuel sources. By combining observations with model simulations, we find that a leakage rate of 3.5% (2.5–4.3%) is required to reproduce the observed seasonal variability and long-term trends in C2H6, far exceeding China’s commonly assumed 0.2% inventory value. This estimated leakage rate also implies average methane emission of 0.68 (0.48–0.83) Tg yr−1 over 2012–2021, vastly underestimated or entirely omitted in existing inventories. Our results reveal a substantial underestimation of methane emissions from natural gas consumption and underscore the urgent need to reassess sector-specific methane budgets in rapidly urbanizing regions of China. Rapid growth in urban natural gas use in China has improved air quality but may carry a larger climate cost than previously recognized. Using atmospheric ethane as a tracer, this study reveals that methane emissions from natural gas consumption in the Yangtze River Delta metropolitan regions are substantially underestimated.
Cities must efficiently and equitably allocate scarce resources. A major example is centralized school assignment, where cities combine admissions policies and student-submitted preference rankings to make assignments. Although both factors are understood to contribute to outcome inequities (the latter through introducing ‘administrative burden’), it is difficult to disentangle the two, limiting intervention design. Here, using data from 58,901 New York City students, modeling optimal application strategy and calculating admissions counterfactuals, we study how individual ranking behavior translates to undermatching: the school quality difference between where a student matched and where they could have matched. We find Black and Hispanic students undermatch 1.5× more than their Asian and white peers and 2× more among the most competitive students. Within our framework, making changes to a single list position with ex ante information could reduce undermatching by 24%. Our results suggest that individualized interventions targeting disadvantaged students with competitive applications to apply to ‘reach’ programs would be most effective in reducing undermatching in New York City. However, large-scale adoption could lead to more nonmatching, suggesting a limit to naive behavioral interventions. Cities are challenged to allocate educational resources efficiently and equitably. This study of the 2022–2023 New York City High School Match program finds that Black and Hispanic students undermatch 1.5 times more than peers, especially among competitive applicants, and that behavioral nudges can help.
A girl named Poetry did not know she had a skin color until a city told her. It would take a lifetime, and another city, to learn where home truly lives.
Urbanization profoundly modifies natural ecosystems that provide essential services to society, and nowhere is this effect more pronounced than in megacities. Using comparative sampling surveys, we investigated how urban expansion in the Metropolitan Region of São Paulo, Brazil—a megacity with over 22 million inhabitants—alters the size structure of stream communities and whether such changes trigger cascading effects on food web structure and ecosystem functioning as indicated by energy and carbon flow. We found that a sharp decline in biodiversity linked to urban infrastructure development was strongly non-random with respect to body mass. The selective loss of very small, moderately large and large taxa truncated food web size distributions, leaving urban streams dominated by small-bodied organisms and compressing size ranges by four orders of magnitude relative to rainforest streams. Food web complexity collapsed, from networks with over 150 trophic links to as few as 3, resulting in a substantial 1,446-fold reduction in energy flow. As processes such as nutrient cycling underpin critical ecosystem services in rivers, the loss of species diversity and degradation of food web integrity are likely to have extensive consequences for urban societies. Urbanization alters the structure and function of ecosystems. This study found that the diversity, complexity and energy flow through stream communities were sharply reduced by the expansion of the São Paulo Metropolitan Region of Brazil.
Many cities have substantially expanded urban tree cover yet continue to experience intensifying heat stress that threatens public health, infrastructure and climate resilience. By contrast, traditional Chinese villages have demonstrated lasting thermal resilience through a synergistic mountain–water–forest framework that functions as a holistic climatic regulator. Building on this principle, we adapt and validate this cooling framework for modern megacities across diverse climatic zones and morphological contexts. Leveraging cold-air advection driven by terrain-guided wind patterns and upwind greening, the mountain–water–forest framework yields a temperature reduction of 0.4 ± 0.2 °C across more than half of the urban area and shows limited sensitivity to synoptic circulation types and terrain settings, requiring only (1) stable wind pathways and (2) adequate upwind greening zones. This study provides a scalable spatial strategy for heat mitigation in cities meeting these prerequisites, enriching climate adaptation strategies from a systems-based spatial perspective. Urban heat stress threatens health and infrastructure. The mountain–water–forest framework, adapted for megacities, utilizes terrain-driven cold-air advection and upwind greening, achieving temperature reductions of 0.4 ± 0.2 °C over more than half of the urban area across diverse climatic zones with limited sensitivity to synoptic circulation types and terrain settings.
Rural–urban transition zones are intensive frontiers of global urbanization, where immense social and ecological pressures converge over relatively limited areas. Despite evidence on the processes involved and impacts of rural to urban transitions, the dynamics of the transitioning zones remain underexplored. Here we frame the zones as transitional social-ecological systems and quantify their resilience. Specifically, we use cross-sectional comparisons and temporal (2000–2020) analyses in the Beijing–Tianjin–Hebei urban agglomeration, China, to assess the resilience of the transitional social-ecological systems as they shift from being rural to being urban. We find low resilience in these transitioning zones, with resilience declining across system boundaries and a temporary loss of resilience preceding the ‘regime shift’ to urbanity, providing archetypical evidence of impending social-ecological systems regime shifts in rural–urban transition contexts. Our study advances understanding of regime shifts by quantifying resilience dynamics in response to rural–urban transitions. Importantly, it also highlights rural–urban transition zones in the global south as critical yet overlooked arenas where instability emerges and where interventions are essential to steer sustainable urbanization. Growing cities expand outward, creating edge zones transitioning from being rural to being urban. Focusing on China’s Beijing–Tianjin–Hebei region, this study finds these zones become less resilient socially and ecologically as they transition.
School gates are urban boundary spaces where students meet streets, vendors and peers. Cities should regulate school-gate foodscapes for safety, health and inclusion without erasing the small joys that they create.
Cities are changing faster than the tools used to understand them. A new generation of AI can now synthesize images, model aspects of human behavior and reason across heterogeneous data—capabilities that are beginning to reshape how researchers and practitioners observe, model and support decisions about urban life. Here, in this Review, we explore what these tools can genuinely offer, where the evidence is strong and where it remains thin. The answer depends less on technical novelty than on whether generative AI can be evaluated honestly, validated in context and deployed in ways that keep human judgment and accountability at the center. Understanding cities has never been more important. This Review considers the capabilities of generative AI, synthesizing insights into the importance of honestly evaluating AI, validating it in context and deploying it to center human judgment and accountability.
Rapid urbanization and climate change are intensifying humid heat in cities, making air conditioning (AC) increasingly essential for both cooling and dehumidification. However, the evolving and spatially varied contribution of humidity to urban AC energy demand remains poorly understood, posing risks to climate-sensitive urban energy planning and building thermal design. Here, by coupling an updated urban building energy model with a global Earth system model, we project that urban dehumidification energy demand will rise by 47% globally under a high-emission scenario. Its contribution to total urban AC demand diverges markedly across regions owing to interacting changes in temperature and humidity that reshape city-specific building thermal design conditions. We further show that humidity amplifies the temperature sensitivity of urban AC demand across climate zones, leading to AC energy demand two to three times higher on humid days. These findings highlight the critical need to incorporate humidity dynamics into urban energy and infrastructure planning, particularly in rapidly urbanizing regions of the global south. This study identifies rising urban air-conditioning energy demand for dehumidification under climate change, alongside spatially divergent contributions to total urban air-conditioning demand.
In fragmented and intensively managed remnant urban green spaces, enabling natural regeneration is crucial to sustain ecosystem functioning and associated services. Natural regeneration therefore offers an important lens into ecological resilience in human-modified landscapes. Here we present one of the most comprehensive field-based assessments of urban plant diversity in the Afrotropics, comprising over 25,000 naturally regenerating woody plant individuals of 206 species (39% native) across 329 vegetation patches in Antananarivo, Madagascar. Landscape-level native species diversity declined with greater building complexity, density and socio-economic development, whereas exotic species showed no consistent associations with determinants of urban characteristics. Native species richness was highest in ‘sacred’ forest fragments, many of which contain historic remains dating back to pre-colonial times. Notably, seven of the ten most species-rich patches were located in such sites. Our findings highlight the potentially important role of these sites in sustaining native species diversity and indicate how socio-cultural factors can present both opportunities and barriers for tropical urban conservation and restoration. Urbanization challenges plant communities. This study in Antananarivo, Madagascar, finds declines in the diversity of native, but not exotic, plants with greater urban intensity and that ‘sacred’ forest fragments supported the highest native plant diversity.
Between 2010 and 2019, Uber and Lyft launched in hundreds of cities across the USA. Economic theory and prior literature, coupled with company claims, posit that ride-hailing increases job flexibility for drivers and mobility for passengers, thereby stimulating local economic activity. Here we test these claims by leveraging the staggered entry of Uber and Lyft across 167 service regions nationwide to estimate the aggregate effects on jobs, wages and regional GDP using difference-in-differences approaches that generate consistent estimates in the presence of heterogeneous treatment effects. We find that Uber and Lyft entry led to an increase in both regional GDP per capita and in seasonal, temporary or otherwise intermittent employment per working age population. We do not detect statistically significant effects on overall employment or earnings. Ride-hailing platforms such as Uber and Lyft are theorized to stimulate local economies. An analysis of 167 US cities reveals that their entry increased regional GDP and intermittent employment, but not overall jobs or earnings.
Improving building energy efficiency is critical for urban decarbonization, yet its system-level costs and benefits remain insufficiently quantified. Here we conduct a cost–benefit analysis of demand-side energy efficiency upgrades in China’s urban buildings from 2020 to 2050 by integrating building stock dynamics, energy simulation and power system planning models. Results indicate that energy system savings (for example, reduced capital and operating costs for the power grid as well as reduced fuel costs) largely offset the associated investment costs (for example, heating and cooling equipment and building envelope energy efficiency), even without accounting for additional social and environmental co-benefits. However, a key barrier to implementation lies in the misalignment between cost bearers and beneficiaries. Although system-wide savings reduce overall electricity supply costs and benefit ratepayers and society, the investment costs are borne primarily by developers and homeowners. This imbalance highlights the need for policy interventions, including financial incentives and reforms to district heating pricing, to enable large-scale adoption and accelerate urban building decarbonization. This study analyzes the costs and benefits of urban building energy efficiency improvements in China from 2020 to 2050. The results reveal strong cost-effectiveness as well as a mismatch between who pays and who benefits, highlighting the need for policy intervention.
This study assessed the levels and inequities of geographic accessibility to comprehensive emergency obstetric and newborn care (EmONC) facilities across all 29 districts of Greater Accra Region using peak and non-peak travel time estimates derived from the Google Maps Directions Application Programming Interface. We calculated median travel times (MTT), the proportion of women aged 15–49 years and reachable facilities within 15-, 30- and 60-min thresholds, stratified by wealth. MTT to the nearest public comprehensive EmONC facility was 29.7 min during peak traffic. Nearly 90% of women were within 30 min of public comprehensive EmONC, and 93% were within 30 min of public or private care. In peri-urban areas, public facilities reachable within 30 min dropped from at least one during non-peak to none during peak traffic. Geographic accessibility was notably better among the wealthiest 40%. Our findings highlight geographic and socioeconomic inequities, calling for targeted investments especially in peri-urban areas. Using travel data, this study reveals that while most women in Greater Accra, Ghana, can reach emergency obstetric care within 30 minutes, peri-urban and poorer areas face considerable geographic and socioeconomic access inequities.
Here we leverage large-scale travel surveys covering over 200,000 residents across Boston, Chicago, Hong Kong, London and São Paulo. With rich individual-level data, we reveal patterns in social mixing, which cannot be identified from high-resolution mobility data alone. Inferring socioeconomic status from residential neighborhoods yields social mixing levels 16% lower than using survey data. Individuals over the age of 66 experience greater social mixing than those in late working life (aged 55–65), lending data-driven support to the ‘second youth’ hypothesis. Teenagers and women with caregiving responsibilities exhibit lower social mixing levels. Living near major transit stations reduces the influence of socioeconomic status on social mixing. Finally, inputs of home-space, activity-space and demographic attributes are embedded and fed into a supervised autoencoder, revealing that mobility shapes experienced social mixing more than sociodemographic characteristics, home environment and transit proximity. Yet, activity spaces remain stratified by income, resulting in structurally different social mixing experiences. Using travel surveys from five global cities, this study explores how daily mobility shapes social mixing. Results show that activity spaces explain most place exposure variations, outweighing demographics and transit proximity.
Life-service digital platforms are increasingly reallocating urban space through routing, dispatching and rebalancing algorithms that prioritize commercial throughput over broader public interests. Cities need proactive algorithmic governance to safeguard spatial control over shared urban space.
In the Austrian city of Innsbruck, the European Alps are never just scenery. They shape how we live, dream and define ourselves — and how we urbanize. The Patscherkofel — our Hausberg, a personal ‘backyard mountain’ — reveals how a tourism city’s soul climbs higher while its roots shift below.
