U.S. Atlantic Coast and Sea Level Rise

Allow Migration to Prevent Diminshing Ecological Utility of Wetlands

Nov 13, 2009 Sara E. Lewis

As sea level rises, coastal inhabitants respond by building barriers. In the long term, planning that allows wetlands to migrate inland is recommended.

If there were no humans staking claims to the Atlantic coast, wetland ecosystems would naturally migrate inland, affording the same beneficial environmental functions that they currently do. Wetlands soak up water, protecting the coast from the ravages of wave action and extreme weather events like hurricanes. They also clean water and help it infiltrate underground aquifers rather than run off to the ocean. Without wetlands planet Earth would be without functioning without its kidneys.

In addition, wetlands are the spawning ground for many fish and the safe playpen for young creatures like crabs and shrimp. These animals are protected by the calm and cover of the wetlands habitat. Plants and animals live there to provide food for other marine animals and migrating birds.

Rising Sea Levels Threaten Coastal Wetland Environments

Rising sea levels threaten existing coastal wetlands. The wetlands would naturally migrate inland, if the surrounding land was vacant. However, this land is not open. A recent environmental research report in Environmental Research Letters, State and local governments plan for development of most land vulnerable to rising sea level along the US Atlantic coast, authored by 13 experts and based on 131 state and local land use plans, revealed that almost 60 percent of the land along the Atlantic coast is developed or slated for development. Bulkheads, rip rap, and other hard barriers or surfaces are routinely permitted. The necessary wetlands buffer cannot get around such structures.

When sea level rise is taken into account, hard shore protection methods that would seem to comply with federal law would probably violate the Clean Water Act.

Climate Change and Sea Level

During the twenty-first century, sea level is predicted to rise from 20 centimeters to one meter or approximately 8 inches to one and a quarter yards. In the short term, hardened shorelines prevent erosion and loss of structures. But they also prevent inland migration of wetland ecosystems and squeeze the beneficial area between water and homes, parking lots, highways, and other man-made structures.

The short term battle against a steadily rising tide wastes resources in the long run, yet planners have not realistically evaluated the best way to respond. Instead of building barriers, a more appropriate response might be to consider an orderly retreat from the shore to preserve wetlands and limit continued costly damage.

Study Findings Related to Sea Level Rise

The study cited above created four graduated categories of land to rank land by the likelihood of its use to protect the land as sea levels rise. While a majority of the land was already developed, the study found that land use plans on most of the remainder that is not conserved will probably be developed according to existing regulation and “maintaining this development as sea level rises would require increasingly ambitious shore protection.”

In the U.S., protection of populated areas below sea level is only practiced in New Orleans. “Sea level rise could leave communities similarly vulnerable throughout the U.S. Atlantic coast,” and would imperil the environmental benefits of natural wetlands.

“At the current rate of sea level rise, most tidal wetlands are able to keep pace through sedimentation and peat formation.” But as the rate becomes greater, the survival of wetland ecosystems is doubtful.

To increase wetlands migration and maintenance, all coastal floodplain construction would need to be halted or abandoned. However, current public policy promotes development and shoreline hardening.

“Ignoring the habitat eventually lost by blocking wetland migration is unreasonable, in our view …” Preventing the landward migration of aquatic habitat (wetlands, beaches, floodplains, and shallow waters) is the main reason for current shoreline hardening and protection.

“A more comprehensive approach would be to consciously manage the impacts of shore protection as sea level rises with estuary-wide plans that define the fates of shorelines as sea level rises.” For example, management of the Chesapeake Bay region of Virginia and Maryland for predicted sea level rise might be attempted. The study concludes that, “a wide variety of planning and legal mechanisms are available for implementing a planned retreat without hurting property owners.”

The copyright of the article U.S. Atlantic Coast and Sea Level Rise in Geography is owned by Sara E. Lewis. Permission to republish U.S. Atlantic Coast and Sea Level Rise in print or online must be granted by the author in writing.

Wetlands Protect Shorelines