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Why Denser Cities Are Better for People and the Environment

Dense cities that set aside large tracts of natural land help those spaces better provide services people want, such as air cleaning and water cleaning, a new study finds.
Rocinha, the largest favela in Rio de Janeiro, Brazil. (Photo: Chensiyuan/Wikimedia Commons)

Rocinha, the largest favela in Rio de Janeiro, Brazil. (Photo: Chensiyuan/Wikimedia Commons)

It's always nice to see a city balance its buildings and sidewalks with trees and parks. But how exactly to achieve this equilibrium? Portland, Oregon, and Rio de Janeiro offer two extreme possibilities. Portland is scattered with small city parks; there seems to be one every few dozen blocks. Rio de Janeiro, on the other hand, is intensely urban, but contains expansive national parks within its borders.

new study published today argues for the Rio model. Tightly-packed cities alongside large stretches of natural or agricultural land tend to better protect the natural land's ability to clean the air and water, store carbon, and provide other benefits that people want, the study finds. As the world's population increases and cities grow, policymakers may want to consider "top-down, policy-led approaches" to ensure that cities build compactly, writes a research team led by Kevin Gaston, a biologist who studies sustainability at the University of Exeter.

Denser cities mean more productive and helpful natural lands.

Gaston and his team conducted their research by analyzing nine case studies that measured correlations between cities' density and nearby un-urbanized lands' ability to provide one of nine natural services: water cleaning, air cleaning, noise reducing, pest controlling, the ability to overcome a city's "heat island effect," food growing, pollination, carbon storing, and an ability to improve city-dwellers' sense of well-being. (Pacific Standard has often covered research about that last effect.) In the majority of these cases, denser cities mean more productive and helpful natural lands, the researchers found. Plus, moderate levels of development, like that of the suburbs, made natural lands lose their services at a disproportionately fast rate, compared to intense development.

There is one service that less-dense cities provide better than dense ones, the study finds: Boosting residents' sense of well-being. Policymakers can improve dense cities' healthfulness, the researchers write, by adding some greenery in the form of sidewalk trees, green walls, and green roofs.

So is the city mouse or the country mouse happier? The country mouse may think he is, but in terms of measurable benefits, it seems the city mouse has got it made.

Quick Studies is an award-winning series that sheds light on new research and discoveries that change the way we look at the world.