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Climate Change

Climate Change Indicators in the United States


Key Points
  • Roughly 20 square miles of dry land and wetland were converted to open water along the Atlantic coast between 1996 and 2011. (For reference, Manhattan is 33 square miles.) More of this loss occurred in the Southeast than in the Mid-Atlantic (see Figure 1).
  • The data suggest that at least half of the land lost since 1996 has been tidal wetland. The loss of dry land appears to be larger than the loss of non-tidal wetland (see Figure 2).
Background

Rising sea level tends to make headlines during extreme events, like the storm surge that caused billions of dollars in damage during Hurricane Sandy in 2012. Yet rising sea level can also cause permanent changes in the landscape when it inundates (submerges) low-lying land. The Atlantic coast is particularly vulnerable because of low elevations and sinking shorelines.

The loss of coastal land can affect a large number of people, as nearly 10 million Americans live in a coastal floodplain. 1 Coastal ecosystems are also at risk. These environments provide habitat for many kinds of plants and animals, as well as services that ensure people’s well-being, ranging from food production to recreation. Coastal wetlands provide valuable nursery, feeding, breeding, staging, and resting areas for many fish, shellfish, mammals, and birds, and they can buffer coastal areas against storm and wave damage.

As sea level rises, dry land can turn into wetland or open water. Existing wetlands can be threatened, too, as salt marshes, mangrove forests, and other coastal wetlands are at risk of being converted to open water.

The Sea Level indicator shows that sea level is rising overall in connection with climate change, but the rate of change varies by region, as do the effects. To provide a useful regional perspective, this feature examines the amount of land lost to sea level rise along the Atlantic coast from Florida to New York. It is based on satellite data that have been collected and analyzed at five-year intervals since 1996. Figure 1 divides the Atlantic coast into two regions for comparison, while Figure 2 shows the different types of land that have been lost.

Notes

Measurements of the change in coastal land depend on land cover and elevation data, which have significant limits in terms of accuracy and precision. Some results are field-checked for accuracy. The coastal land cover data are routinely compiled by the National Oceanic and Atmospheric Administration’s Coastal Change Analysis Program, and they represent the federal government’s most comprehensive set of data on land use and land cover in the coastal zone.

Sea level rise is not the only factor that contributes to the loss of coastal land. In addition to the natural sinking of the shoreline in some areas, such as the Mid-Atlantic, coastal land loss has been made worse by human activities such as navigation and flood control structures that block wetland migration or the movement of sediment; withdrawal of ground water, oil, or natural gas in some regions; and boat traffic that accelerates wetland erosion. 4 Natural processes unrelated to current sea level rise can also cause shores to erode.

Data Sources

This feature is based on land cover data from the Coastal Change Analysis Program, which is coordinated by the National Oceanic and Atmospheric Administration. For more information about this program, visit: http://csc.noaa.gov/
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