catalpa

On July 13, Washington, D.C. hit its 17th consecutive day above 90 degrees. The following week was no better with a heat advisory in effect from Maine to South Carolina. Casey Trees, a D.C. based nonprofit committed to restoring, enhancing, and protecting the tree canopy of the nation’s capital, says air temperatures in cities, particularly after sunset, can be as much as 22˚ F warmer than the air in neighboring, less developed regions. This urban heat island effect, as landscapers know, is driven by asphalt, concrete, and other hardscapes that retain and amplify heat. But more than just being uncomfortable, excessive heat is a serious health risk that often disproportionately affects those in underserved neighborhoods with less tree canopy. But it’s not just humans who feel the ill effects. According to Casey, urban heat islands have a wide-ranging and deadly set of impacts on the environment: Urban heat islands increase energy demand for cooling. During extreme heat events, which are exacerbated by urban heat islands, the demand for cooling can overload systems and may result in brownouts or blackouts to avoid power outages. Companies that supply electricity typically rely on fossil fuel power plants to meet much of this demand, which in turn leads to an increase in air pollutants and greenhouse gas emissions. High pavement and rooftop surface temperatures can heat stormwater runoff. This heated stormwater drains into storm sewers and can raise water temperatures as it is released into waterways, which can be deadly for aquatic animals and ...