Trees and the Urban Heat Island effect

Changes in tree canopy cover have many measurable effects on the environment. For example, as a city's tree cover is destroyed, its temperatures intensify.

Urban heat islands generate ozone pollution, make people swelter, drive up utility bills, and change rainfall patterns. In turn, increased power plant loads spew additional pollution into the air while more landscape watering depletes aquifers.

Urban Heat Island slideshow Landsat satellites have been circling the Earth since 1972, and their image data provides a historical archive. The images below show the Atlanta metropolitan area. NASA scientists have mapped out the effects of changing tree cover on urban temperatures. This slideshow depicts a 21 year period (1972 to 1993) over which Atlanta's heat island exploded at the same time its tree cover was decimated.
Below is an analyzed Landsat image with dark green areas representing tree cover over 50%, and red & black areas representing landcover dominated by impervious urban surfaces.	Below is a Landsat image showing temperature. Each color change indicates a 1° hotter temperature than the surrounding area. These images were made on a summer day about 5:00 in the afternoon.
Click on a year (at right) to see the tree cover and heat island for that year Images courtesy of and copyrighted by American Forests

More information about Urban Heat Islands

The heat is on... - A study by Southwest Research Institute shows San Antonio is hotter than nearby small towns, and getting even hotter.

NASA Satellite Confirms Urban Heat Islands Increase Rainfall Around Cities - Satellite images show San Antonio's heat island has pushed rainfall to the east of the city, off of the aquifer recharge zone.

The Urban Heat Island and Human Health - A radio program about the serious health hazards created by air pollution.