Why Do Cities Need Trees?

Ever dream of your very own treehouse? From birds and raccoons to ladybugs and caterpillars, many living things use trees as their homes. But did you know that trees provide crucial benefits for people too?

Air Purification

Trees clean the air! The leaves of trees are porous, meaning they have tiny holes and spaces that allow for certain substances to pass through, while trapping others. In this way, leaves purify the air by trapping particles that are harmful to the environment, such as carbon and other pollutants, making air healthier to breathe.

Heat Absorption

Trees provide essential shade, reducing urban “hot spots.” According to the Environmental Protection Agency, the average annual air temperature of large cities can be 1°- 5°F warmer than surrounding areas during the day and up to 22° F more overnight. This is because rural areas with trees and vegetation quickly cool down after sunset, while cities’ buildings and streets maintain their heat. In fact, during summer heat waves, buildings without shade absorb up to nine times more solar radiation! To cool buildings, we must burn more fossil fuels, increasing energy costs and spewing more unhealthy pollution into the air.

Trees Help Reduce the Impact of Flooding

Trees absorb stormwater runoff, reducing the impact of heavy rains and flooding and filtering out toxins. Without trees, some city planners estimate there would be a need for twice as many city storm drains and water treatment plants!

Mental Health

Researchers have found that when people are in the presence of green foliage, they have decreased stress levels. They even found that hospital patients with views of trees from their room recover faster than those who simply have a view of brick walls!

When most people think of the environment and nature, they think of farms, forests, and bodies of water. Rarely, however, do they think of its connection to cities, buildings, and people. It is your job to help them understand that trees benefit and impact so many different things! They impact our forests, cities, atmosphere, health, and more!

By Lauren Choy

Sources:

NPR; Morning Edition, "Scientists In Houston Tell A Story Of Concrete, Rain And Destruction"; November 9, 2017; https://www.npr.org/2017/11/09/563016223/exploring-why-hurricane-harvey-caused-houstons-worst-fooding

Youtube; Ted-Ed, "What happens if you cut down all of a city's trees?" by Stefan Al; https://www.youtube.com/watch?v=zarll9bx6FI

United Nations Economic Committee for Europe; Trees in Cities; https://treesincities.unece.org/