Climate change's rising water levels could directly affect half of Americans

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Slightly more than half the American population resides in coastal watershed counties, areas increasingly catching the effects of climate change, says a recent federal technical report undertaken as part of a quadrennial national climate assessment.

The report (.pdf), led by staffers from the National Oceanic and Atmospheric Administration and the U.S. Geological Survey, says scientific studies conclude with high confidence that the global average sea level will rise between 0.2 and 2 meters by the end of this century.

That rise won't manifest evenly across U.S. coastal regions (the study includes areas around the Great Lakes)--low-lying regions such as Louisiana and the Chesapeake Bay will experience a greater relative rise due to land becoming subsumed by seawater. Neither will the effects on American society be evenly distributed, since the southern United States has a concentration of major cities whose elevation above sea level is between only 1 and 6 meters.

The report notes that theoretically, people could relocate landward to accommodate rising seas, but "human infrastructure, private land ownership and current policy" tend to prevent such adaptation measures.

Economic activity in coastal watershed counties--just 17 percent of the total U.S. landmass, excepting Alaska--generates 58 percent of gross domestic product, the report also notes. Coastal counties are disproportionately involved in professional and business services, information services and financial activities.

"An increase in the intensity of extreme weather events such as storms like Sandy and Katrina, coupled with sea-level rise and the effects of increased human development along the coasts, could affect the sustainability of many existing coastal communities," said Virginia Burkett, the USGS co-lead author in a statement.

Besides the direct climate change impacts of heat waves, drought and flood, hurricanes and storm surges, the report also warns Americans to expect an increase in insect-transmitted and zoonotic diseases. Changes in precipitation, temperature and humidity "will shift habitats that allow insect and animal [disease] vectors to survive and transmit disease in new, previously unsuitable areas," the report notes.

Military readiness could also be impacted, since the Defense Department, like much of the U.S. populace and economy, has a robust coastal presence of bases and infrastructure.

Adaptation planning activities is the United States have been ad hoc, the report also notes, adding that although state governments and the federal government play a role in adaptation planning, local governments are the ones that must make the critical, basic land-use and public investment decisions necessary to implement adaptive measures.

The DoD, too may be in need of planning, since the report says that although climate-change forecasts are being discussed with higher frequency among DoD managers, "a low level of awareness exists of the empirical knowledge base supporting global climate-change predictions or scenario use nor any recognition of the need for contingency planning."

For more:
- download the report, "Coastal Impacts, Adaptation, and Vulnerabilities" (.pdf)
- read a release on the report at the NOAA website

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