Reviews & Analysis

Climate mitigation plans too often overlook urban construction. Levels of historic greenhouse gas emissions resulting from construction in cities have now been estimated, and rates determined at which cities must reduce construction emissions to stay within climate limits.

Air connectivity is an important aspect of global business, but what makes a city ‘well connected’ is unclear. We found that, more important than the number of flights between cities, companies choose to locate their subsidiaries in locations that are well integrated within the global air traffic network.

Climate risk is underpriced in US municipal bonds, creating vulnerabilities as insurers retreat and adaptation planning remains disconnected from finance. This Review reveals a climate-debt doom loop and proposes governance reforms and disclosure standards to strengthen municipal resilience.

Low-income urban communities are facing infrastructural inequities. This Perspective advocates for an agenda that aims at reorienting infrastructure research by bridging methodological divides, integrating fragmented datasets and actors, and centering engagement with affected communities.

Urban digital twins rely on static sensors and miss dynamic human and socioeconomic dimensions. Integrating anonymized mobile crowd data provides real-time, context-rich insights that improve accuracy, responsiveness and citizen co-creation.

Nature-based solutions have long been touted as important for addressing urban challenges, such as from climate change. This Perspective argues for using synthetic biology to help to meet such challenges and make our cities more sustainable.

There was a considerable trend of urban expansion onto hillsides from 2000 to 2020, which covered 11.65 million hectares globally. This expansion has destroyed 6.73 million hectares of natural habitats and further directly affected about 70% of threatened species, which highlights the fact that urgent policy action is needed to balance such development with terrestrial biodiversity conservation.

Informal workers contribute meaningfully to cities worldwide. This Perspective argues that current regulatory approaches in San Francisco and New York City constrain informal work and workers, considering cases from the Global South in service of a more inclusive approach.

The effects of warfare on urban sustainability tend to escape traditional measurements and inventories, but now a satellite-constellation-based approach exposes how warfare is unleashing plumes of methane across battlefronts in Ukraine. Emission patterns flip: cities surge from levels that are a fraction of rural emissions to levels that are many times higher.

Climate change is making walking in cities more difficult. This Review examines the connection between climate change and walkability, focusing on thermal comfort in complex urban environments.

Text has traditionally been used as a qualitative resource in urban research, but new tools enable large-scale quantitative analysis. This Review explores the opportunities and challenges of using text data to generate insights into cities.

As cities grow, more people face poor living conditions and greater wealth inequality. By overcoming conceptual, data-based and computational challenges, and focusing on cities in sub-Saharan Africa, a new study demonstrates how to measure this trend at scale.

We reveal the hidden geography of poverty in African cities by combining survey data, geospatial data and machine-learning algorithms to develop high-resolution maps of slums that show where services are lacking and inequality is rising. These insights should help to guide investment and interventions.

Our study reveals the shortage of green infrastructure per capita in the most informal neighborhoods of sub-Saharan African cities by linking individual trees to neighborhood informality. Continued urban expansion is projected to result in tree cover loss beyond current urban boundaries, which highlights the contradiction between the urgent need to upgrade informal settlements and current socioeconomic constraints.

Nature enhances mental health, but it is unclear exactly what kind of urban green and blue spaces are needed. A global systematic analysis reveals that urban forests account for the largest proportion of improved mental well-being, especially among young adults.

Cities are renowned for catalyzing human interactions, but their effects on urban species are less clear. This Perspective argues for such a focus, and proposes a framework for studying interactions between urban species.

Cities are home to many species, so managing urban ecosystems accordingly is important. This Perspective argues for better integration of widely used biodiversity modeling frameworks and tools into urban ecology and the management of urban landscapes.

Cities affect biological evolution, but traditionally researchers focus on the biophysical influence of urban environments. Instead, this Review explores how the social processes of religion, politics and war drive wildlife evolution by shaping urban conditions.

Focusing on the urban growth–environment nexus, this Perspective analyzes economic, population, spatial and environmental dimensions through green growth, degrowth and post-growth lenses, revealing mixed decoupling evidence.

Engineering of waterproofing for buildings needs innovative low-carbon solutions to promote urban safety and sustainability in the face of climate change. This Perspective introduces a sustainability-driven strategy, explores future directions and offers low-carbon recommendations to advance the field.