Research Briefing

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.

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.

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.

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.

Citizen scientists counted and classified light sources while walking through various urban environments, with the goal of understanding the types of light sources that illuminate our nights. Comparison of this survey with nighttime satellite imagery enables estimating the total number of light sources at the level of an entire city or country.

A comprehensive radar satellite analysis of 28 major cities in the USA reveals that more than 20% of the land area in each city is sinking, which affects 34 million residents. Driven by natural processes and groundwater extraction, these sinking areas threaten approximately 29,000 buildings and exacerbate flood risks.

The color of cities is a striking feature of their culture, heritage and built environment. By examining the chromatic reconstruction of 3,103 heritage buildings over 40 years in Singapore, we note dynamic changes in local color in the city and suggest that color should be preserved as part of the sociocultural ecology.

We used natural language processing to analyze thousands of zoning documents and investigate the effect of form-based codes (a type of zoning reform) on urban sustainability. Form-based codes are widespread and contribute to improved walkability, shorter commutes and a higher share of multifamily housing.

With the rapid growth of urban natural-gas distribution systems comes the frequent occurrence of pipeline leaks. A strategy that combines vehicle-mounted tools and sniffer canines for leak detection leverages both technological and biological advantages: its effectiveness has been demonstrated in field tests on 4,000 km of pipelines across 20 Chinese cities.

In extensive food-delivery order records across 100 Chinese cities, a marked surge in urban residents’ reliance on food-delivery services can be seen during hot days, which suggests a newly emerging heat adaptation strategy. Further quantification of mitigated heat exposure reveals unequal benefits experienced by different populations.

A mixed-methods study of crime in the English city of Nottingham shows that the presence of a governance-type organized criminal group helped to reduce ordinary crime in the immediate area.

Drawing on unique survey and administrative data from more than 800 organizations in 5 cities worldwide, this study shows how civil society organizations adapt their integrative practices to the neighborhoods in which they are located. Organizations in low-income neighborhoods emphasize social connections, whereas those in affluent, migrant-rich neighborhoods prioritize access to institutions.

An analysis of what happens to post-consumer textiles in nine cities across three continents uncovered remarkable patterns. The growing volumes of textiles bypass waste management systems and are directed towards exports, which externalizes environmental and social costs of the ‘end-of-life’ treatment. Recommendations are made for city governments to improve local circular textile systems.

We have constructed a framework to assess sunlight duration in cities, revealing a substantial reduction in available sunlight owing to cloud cover and three-dimensional urban structures. Our study underscores the imperative for integrated approaches to urban planning, using ‘digital twin’ technologies — virtual representations of real urban environments — that emphasize sufficient access to sunlight.

Our research explores how urban slum dwelling affects clinical markers in patients in their first episode of psychosis in São Paulo, Brazil. Results show slum living correlates with a higher psychosis severity (particularly disorganization and negative symptoms), which highlights the influence of social exclusion on psychosis presentation.

In the current period of rapid urbanization, nearly 40% of global cities exhibit exacerbated extreme drought due to the warmer and drier urban environment. Furthermore, more than half of global urban regions are projected to experience increasing challenges from extreme drought by 2050.

The rural land covers that surround a city can mitigate the urban heat island effect for the entire city. In addition, specific rural locations and proposed landscape design strategies can maximize the potential for urban heat mitigation.

We uncovered the degree of interconnectedness of urban centres globally, finding that 3.2 billion individuals can access multiple urban tiers ranging from towns to large cities within an hour of travel. These findings emphasize the strategic importance of intermediate cities in linking various urban and rural areas, which is crucial for effective regional development.