Satellite photographs show losses in wetlands in US

Satellite photographs show losses in wetlands in US

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The government doesn’t know how many acres of Florida wetlands have been destroyed in the past 15 years. No state or federal agency has kept track, not even the Army Corps of Engineers, which has the final say on protecting wetlands.

Another federal agency, the National Wetlands Inventory, is supposed to track losses nationwide. The tiny agency, based in St. Petersburg, mapped Florida’s wetlands 20 years ago, but hasn’t updated its maps except for two of Florida’s 67 counties. So the St. Petersburg Times examined satellite images of Florida to determine the loss of wetlands. Satellite images taken in the late 1980s were compared with those taken in 2003. Those were combined with data from the National Wetlands Inventory and the state Fish and Wildlife Conservation Commission.

A random sample of 385 places on the resulting maps were checked against other data through property records, aerial images and site visits. No satellite image analysis can be 100 percent accurate, particularly one covering such a broad area. In this case, the accuracy was about 85 percent, the level required by the U.S. Geological Survey for similar satellite analysis.

To filter out temporary changes from long-lasting ones, the analysis relied on a map of urbanization created by the state wildlife agency. That showed about 84,000 missing acres of wetlands.

The methodology was reviewed by Barnali Dixon, professor of geography at the University of South Florida; Leonard G. Pearlstine, assistant scientist at the University of Florida’s Fort Lauderdale Research and Education Center; and Tom Lillesand, professor of geography and director of the Environmental Remote Sensing Center at the University of Wisconsin-Madison.