In addition to natural population increase, cities often grow to accommodate migrants coming from rural areas or other regions and countries, often in search of economic opportunities or to escape economic deprivation and climate impacts. Rapid outward expansion is greatest in lower-income cities, where population growth is also the highest. Close to 90% of urban growth by 2050 is projected to occur in Asia and Africa, where vulnerability to climate risks is also the highest.
As cities grow, many expand outward into more fertile agricultural land, and ecologically sensitive areas like forests and wetlands. The resulting expansion of built areas can encroach on natural lands and habitats important for climate resilience and biodiversity. At the same time, expanded built areas increase impervious surfaces in cities (such as roads, buildings and concrete), which absorb heat and radiate it back into the urban environment, leading to higher localized heat intensity.
There is value to densifying the built environment rather than growing outward, as this shortens distances between locations and ensures more efficient and cost-effective provision of infrastructure, which in turn improves accessibility. Much empirical evidence illustrates how a city’s spatial expansion and reduced population density increases its per capita costs to provide public services, as well as the social costs associated with higher emissions, congestion, pollution, loss of productivity and unsustainable consumption of land and natural resources.
However, density does not automatically imply very tall buildings, as these are associated with higher construction and other costs, even if the land costs may be lower. Increased density can also lead to increased housing costs, which can exacerbate inequities within cities. For residential housing in particular, cities must balance both livability and affordability as they plan for denser urban environments.
This indicator, land consumption per person, measures how much land (in square meters) is used per person. In 2020, the global average land consumption per person in urban areas was 45.5 square meters per person. This shows a slight decrease from 45.7 square meters per person in 2015. However, from 2000 to 2015, land consumption per person had increased from 43.7 square meters per person to 45.7. Over time, ideally the land consumption per person will decrease or at least remain level, as it did between 2015 and 2020.