One of the most significant potential impacts of climate change is sea level rise that may cause inundation of coastal areas and islands, shoreline erosion, and destruction of important ecosystems such as wetlands and mangroves. As global temperatures increase, sea level rise already underway is expected to accelerate due to a thermal expansion of upper layers of the ocean and melting of glaciers.

US Impacts

Shorelines have been retreating in much of the US for well over a century; scientists have mapped this change in some areas such as Long Island and Delaware. In areas with gradually sloping coasts such as the US Atlantic and Gulf Coasts shore lines are likely to recede as much as 200 times the amount of the sea level rise. A one-foot rise in sea level might well translate to a 200-foot retreat of shoreline with loss of several rows of homes. A recent joint Heinz Center and FEMA study projected large-scale losses in these regions just from current trends including disappearance of several rows of coastal homes in some US coastal communities.

If sea level rise accelerates as climate change scenarios project, the losses of property will be even greater than anticipated. Extensive losses of coastal wetlands and beaches seem likely.

In past eras of sea level rise wetlands and beaches could retreat naturally inland but roads and coastal structures have closed off this option of natural retreat in much of the US coastline. The result is that the total area of beaches and wetlands may diminish greatly in the US over this century.

International Impacts 

Some developing countries are especially vulnerable to sea level rise due to their low- lying nature and limited financial resources to respond. Among the most vulnerable are countries with large populations in deltaic coastal regions such as Bangladesh, Viet Nam, China and Egypt.  

Two populous island nations, the Philippines and Indonesia, have millions who face displacement from their homes from sea level rise. Several small island state nations including the Maldives in the Indian Ocean and the Marshall Islands and Tuvalu in the Pacific could face extinction within this century if rates of sea level rise accelerate. Most of their populations live very close to sea level and a rise of as little as a meter could prove devastating. Even before their lands had become uninhabitable due to inundation some would face loss of their fresh water supply due to salt-water intrusion.  

In the Caribbean many small island nations are periodically ravaged by hurricanes that sometimes in a few hours wipe out development gains of a decade. Although sea level rise may pose a serious threat to some Caribbean nations perhaps the greatest challenge associated with climate change may be an increased incidence of super hurricanes such as Hurricane Gilbert that wreaked such havoc in 1988 or Hurricane Mitch in 1998 whose severe rains resulted in deaths of thousands, largely in Central America.  

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