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State and Local Governments Plan for Development of Most Land Vulnerable to Rising Sea Level along the U.S. Atlantic Coast

If you live in a low-lying coastal community, you probably already know whether your home is in a floodplain. Perhaps you've seen maps that show all the land that could be submerged if global warming causes the sea to rise a few feet. Do you really believe that your home will be flooded? Or do you think that someone--maybe the government, maybe you--will do something to protect your home?

Most people assume that their own community should be protected. But that poses a problem: ecosystems need to migrate inland. And as a society, we may not be able to protect every home in the coastal floodplain even if there weren't environmental problems--it costs alot of money and having too many people living below sea level just seems like a bad idea.

Sooner or later, we are going to have to decide which lands to protect and which lands will yield to a rising sea. And that will require drawing lines on a map--lines that will be controversial, costly, and require much debate, discussion, and negotiation.

A recent EPA report argues that making this decision is becoming increasingly urgent. It is impossible to plan for sea level rise if you don't know whether a parcel of land will be given up to the sea, elevated with the rising sea, or protected with a dike. To help encourage that process, we sat down with the local land use planners for more than 100 local governments to create maps that distinguish lands that are likely to be protected from the lands that are likely to be given up to the rising sea. These maps were not meant to be regulatory maps or anyone's idea of what should be protected. They are just a first approximation of where people would at least try to hold back the sea if current policies continue

The results of that effort are summarized in the journal Environmental Research Letters in a paper entitled "State and Local Governments Plan for Development of Most Land Vulnerable to Rising Sea Level along the U.S. Atlantic Coast." But that 7-page article is just the tip of the iceberg of our 8-year study. This site provides more of the details. The list of states to the left of this paragraph contains links to state-specific discussion of the likelihood of shore protection underlying the new study. You can also download single county maps, statewide maps, zip files with a set of maps, or GIS data for the sea level rise planning maps. We are also posting the publicly available portions of the 2000-page EPA report documenting this study, which contains a county-by-county discussion of land use, shore protection, and coastal policies.

We hope that these maps can help to change the way people think about rising sea level. Researchers and the media need to stop suggesting that Manhattan or even Miami will be lost to a rising sea. That's not realistic; it promotes denial and panic, not a reasoned consideration of the future. Our maps show some of the choices coastal residents face, but losing Manhattan is not one of them.

Paper's Abstract

Rising sea level threatens existing coastal wetlands. Overall ecosystems could often survive by migrating inland, if adjacent lands remained vacant. Based on 131 state and local land use plans, we estimate that almost 60% of the land below 1 m along the US Atlantic Coast is expected to be developed and thus unavailable for the inland migration of wetlands. Less than 10% of the land below 1 m has been set aside for conservation. Environmental regulators routinely grant permits for shore protection structures (which block wetland migration) based on a federal finding that these structures have no cumulative environmental impact. Our results suggest that shore protection does have a cumulative impact. If sea level rise is taken into account, wetland policies that previously seemed to comply with federal law probably violate the Clean Water Act.

For previous reports on the implications of rising sea level, go to More Sea Level Rise Reports.

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Governments Plan for Development of Most Land Vulnerable to Rising Sea (PDF, 7 pp., 1.3 MB) was originally published in Environmental Research Letters , Issue 3, Volume 4 (2009).

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