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U.S. FORESTS AND ATMOSPHERIC DEPOSITION
Citation:
Winjum, J. U.S. FORESTS AND ATMOSPHERIC DEPOSITION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/D-89/197 (NTIS PB90132978).
Description:
Forests in the United States occupy 33 percent of the nation's land area and exist on some lands in all fifty states. hey cover approximately 299 million hectares and are rich in essential resources. Overall, U.S. orests are highly productive. owever, in recent decades, several cases of forest decline on a regional scale have occurred which are not easily explained by normal natural causes. Atmospheric deposition of air pollutants is suspected to play a causal role in many of these cases. he evidence, however, is largely circumstantial in that forest areas with decline symptoms are frequently located where the deposition of pollutants is high. roof of cause and effect has been illusive. zone at concentrations elevated by human activities has been proven to cause declines in some area, but many other wide-spread declines remain unresolved.