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. |
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Click on a year (at right) to see the tree cover and heat island for that year |
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