Coastal Impacts: Rising Seas, Coastal Inundation, Forced Evacuations
A potentially devastating outcome of global warming is the impact that expanding seawater and melting glaciers and ice sheets
will have on sea level. Scientists predict that global warming will likely raise sea level by 50 cm (based on a possible range of
15- 95 cm) by 2100, much faster than the worldwide average sea level rise of 10 to 15 centimeters during the last century
(IPCC, 1995b; IPCC, 1990a; U.S. EPA, 1989, p. 124). This poses a serious threat to low lying and coastal zones, many of
which are already weakened by overdevelopment, pollution, and other problems. Sea level rise could lead to wetland loss,
loss of dry land, beach erosion, saltwater intrusion into groundwater, rivers, and estuaries, infrastructure damage, and loss of
habitat for numerous species of plants and animals. In addition, communities may face the enormous costs of building dikes,
replenishing beaches, elevating infrastructure, and taking other defensive measures to fend off the encroaching seas.
An increase in sea level would affect a large portion of the world's population. For example, nearly half of the U.S. population
lives in coastal counties (SAUS, 1994, Table 38). Individual states, such as Florida and California, have hundreds of miles of
coastline and are therefore particularly vulnerable to rising seas. The EPA estimates that a one foot sea level rise would erode
shorelines by over 100 feet throughout the Southeast (U.S. EPA, 1989, p. 334), and efforts to replenish sand over the next
century would cost billions of dollars.
Sea level rise endangers more than just coastal infrastructure. It also threatens an important resource for recreation and
tourism, commercial fishing, and other economic activities, as well as a critical habitat for numerous species of plants and
animals. The potential tourism losses alone could be substantial. According to a recent study by the Natural Resources
Defense Council (NRDC), there were over 180 million visitors to ocean and bay beaches in 1993, and these visitors provided
tens of billions of dollars to local economies (See Table 1) (NRDC, August 1994, p.7).
Other countries face an even greater threat from sea level rise. The vast majority of Australia's population lives in coastal cities,
and rising seas could harm the country's entire economy. Egypt, which depends on the Nile delta and lakes just inland of the
coast for much of its food production, could face a displacement of 16 percent of its population if sea level rises just 1.5 feet
(Corson, 1990, p. 233). A rise of just a few inches could completely inundate island nations in the South Pacific and the
Caribbean (Revkin, 1992, p. 130). The Netherlands would have to spend billions of dollars to supplement its extensive dike
system (Goemans, 1986).
Around the world, the economic and environmental impacts of sea level rise will be staggering. In the U.S. alone, the EPA
estimates that a one meter sea level rise by the year 2100 (the upper end of the IPCC's estimate) will require $91.25 to
$138.75 billion in cumulative capital costs to protect developed areas with bulkheads and levees and by pumping sand (U.S.
EPA, 1989, p. 123). It will also result in a loss of 25 to 80 percent of U.S. coastal wetlands, which would harm fisheries and
recreation, flood protection, and habitat for numerous species of migratory birds (EPA, 1989, p. 123; Fankhauser, 1995, p.
32; IPCC, 1995a). Myers and Kent (1995) estimate that worldwide coastal protection costs and land loss could be in the
order of $17.5 trillion to $20 trillion over a 50 year period (Myers and Kent, June 1995, p. 152).
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