The Benefit of Urban Forests

Researchers believe that climate change and expanding built-up areas will intensify urban heat islands (UHI), and could contribute to global warming. Typically, UHIs have worse air and water quality than the surrounding rural areas. Buildings that are close together block pollutants from dispersing and becoming less toxic.

What is an UHI?

UHIs are metropolitan areas that are warmer than the surrounding rural areas. Cities can be up to 12˚C hotter during the day in the summer.

High ambient temperatures are linked with early death. The risk of death can increase by between 1–3% for each 1˚C increase in temperature, as well as increase the risk of cardiovascular and respiratory illnesses.

The research

Researchers completed a health assessment on mortality for adults aged 20 and older in 93 European cities. They estimated how much the temperature would decrease by if tree coverage was increased to 30% in each city; then they estimated the number of deaths that this increase could prevent.

A total of 6,700 premature deaths could be attributed to the effects of UHIs, and researchers believe that increase tree coverage by 30% could prevent 2,644 premature deaths. This increase could reduce the temperature by a mean of 0.4˚C.

The results

Increasing tree coverage in cities would cool the environment, making cities more sustainable and climate-resilient. Further research found that urban forests cooled the average temperature of 601 European cities by 1.1˚C and by as much as 2.9˚C.

While planting trees in urban spaces will improve public health and the environment, it might not be enough. Trees take years to grow, and many new trees die within two years. Therefore, it is important to preserve existing trees and reducing other factors that increase the heat in urban areas, such as reducing the number of cars on the road.