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Environnement écologie

Etats - Unis: Study Warns of Threat to Coasts From Rising Sea Levels
ADIT, janvier 2009

     Sea level rise fueled by global warming threatens the barrier islands and coastal wetlands of the Middle Atlantic States, a federal report warned on Friday.
     The report, issued by the Environmental Protection Agency, the United States Geological Survey and other agencies, is one of a series examining the potential effects of a rising sea level on the nation's coasts.
     The rise in sea level is accelerating, the report said, because warmer water occupies more space and because of runoff from melting inland glaciers and ice sheets. The Middle Atlantic States are particularly vulnerable because the rates of rise are “moderately high” there, the region is subject to storms, it is densely populated and much of its infrastructure is in low-lying areas.
     The report, which is available at, says that in the 20th century, rates of erosion in the region varied from 2.4 millimeters to 4.4 millimeters a year, or about a foot over 100 years. In the future, the report said, "it is virtually certain" that coastal headlands, spits and barrier islands will erode faster than they have in the past.
     If sea level rises at a rate of seven millimeters a year or about two feet per century, "it is likely that some barrier islands in this region will cross a threshold," and begin to break up, the report said. The islands forming the Outer Banks of North Carolina are particularly threatened.
     The Intergovernmental Panel on Climate Change, a United Nations climate effort, estimated in its most recent report that sea level might rise by about as much as two feet by 2100. Many experts regard the estimate as optimistic.
     Even a modest acceleration of sea level rise will have a negative effect on the region's coastal wetlands, the report says, adding, "It is likely that most wetlands will not survive" a two-foot rise.
     In natural environments, wetlands survive rises in sea level by shifting inland to higher ground. But in the Middle Atlantic States, the report notes, valuable infrastructure like buildings and roads stands in their way.
     The report said public officials should consider the vulnerability of coastal areas and take action when necessary, for example, by limiting development in vulnerable areas.
     But it noted that there was great uncertainty about the timing and extent of the effects of sea level rise and that the region had conducted "only a limited number of analyses and resulting statewide policy revisions" to address the issue.