Understanding how segregation plays out in cities is enlightening and sometimes surprising. In his Article, Benjamin Elbers traces changes in segregation in US cities, showing that since 1990, desegregation has been the overall trend, largely due to demographic shifts among people of colour, especially in residential mobility; but an increase in segregation was occurring simultaneously due to similar demographic flows in the white population. Focusing on a more micro scale, Thomas Maloutas’s Review sheds light on how segregation can also be vertical — meaning that social hierarchies can be found even in the same building. In nineteenth-century Paris, for instance, the well-off preferred to live in the lower floors of multistory residential buildings because these floors were bigger and better lit, while the upper floors were smaller, darker and were where the service class was relegated to. Now the order has flipped, with views of the city in tall buildings being a commodity that fewer people can afford.

But why does segregation matter? It matters because it is not only an issue of who lives where and next to whom, but also of who lives next to what, as this affects people’s lives and urban experiences. For example, Maurizio Porfiri and Rayan Succar unveil the influence of violence and firearm accessibility in US cities, exploring the deep inter-relationship between gun ownership and violence across the urban–rural divide. Chinmoy Sarkar and coauthors show the relevance of exposure to green spaces and air pollution in reducing physiological stress in the UK. And as another type of urban green space, Hanxi Wang discusses the practice of homesteading in urban China, which allows for informal rural spaces within cities despite the rapid urbanization that has excluded the rural from the urban fabric.

Spatial differences also influence how we can create sustainable cities. As one example, using the case of Seoul, Geun Young Yun and coauthors model the potential of green roofs to fight regional climate change, which could impact cooling and energy use, depending on the meteorological conditions in different parts of the city. In another instance, Veronica Nicholson and Alessio Miatto’s Comment makes the case for architects to design for reuse, connecting industrial ecologists and the construction industry and minimizing and managing waste throughout a building’s life cycle, thereby easing local and global material burdens.

To combat the pernicious effects of segregation and to address climate change in cities, people will have to decide on new ways to run their cities. In her World View, Suet Khoo discusses the importance of residents defining and maintaining urban heritage sites — a process that can be unseen and undermined by top-down decision making. From another vantage, Geci Karuri-Sebina’s piece argues that to avert the overlapping crises, or polycrisis, that is engulfing urban life, we need an urban revolution to shift imaginaries, make cities more inclusive and institutionalize residents having real power in planning decisions.

Cities are sites of difference, but they don’t have to be spaces of inequality. Shedding light on unequal spatial configurations is a first key step in addressing them. Perhaps by doing that, cities can become places with a more-than-human equality, as eloquently painted by Min Lim in her I and the City piece. Lim makes a call for cities to be more delicate so that many kinds of birds can survive and thrive, not just the meanest ones. Against the looming threat of climate change, environmental justice in cities must consider the different species living in them too, to create a more equal world for all urban residents, not just human ones.