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Vegetation in North America
This page contains archived content and is no longer being updated. At the time of publication, it represented the best available science.
Moderate-resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) observations from January - May 2001 for the
United States shows the cycle of vegetation from one season to the nextfrom vegetations winter nadir, to the new growth of spring. EVI
observations can help determine how human- and climate-induced changes are affecting vegetation in the U.S. and around the world. Vegetation
ranges from 0, indicating no vegetation, to nearly 1, indicating densest vegetation.
The January image reveals snow in the Upper Midwest and Rocky Mountains, some of which is
still present in March and entirely gone by late May. In January, the predominantly deciduous
forests of the Appalachians have a lower vegetation index than the evergreen forests of the Sierra Nevada and Cascade mountain ranges, and the forests of Maine. In late spring, however, the situation is reversed. Another interesting change occurs in the Mississippi River Valley. In January, there is very little vegetation, likely the result of farmers plowing the fields
and exposing bare soil. Californias Central Valley remains green year-round, a
major source of winter produce.
As of early August 2008, the Oklahoma panhandle was experiencing its driest year (previous 365 days) since 1921, according to records kept by the Oklahoma Climatological Survey. Through July, year-to-date precipitation in Boise City, in the heart of Cimarron County, was only about 4.8 inches, barely half of average and drier than some years in the 1930s, the height of the Dust Bowl.