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Wetlands Loss

Rising sea level inundates low-lying areas, converts wetlands to open water, erodes beaches, exacerbates flooding, and increases the salinity of estuaries and aquifers. Here are some reports that examine coastal wetland loss as sea level rises.

Evolution of a Marsh as Sea Level Rises

Evolution of a Marsh as Sea Level Rises

Coastal marshes have kept up with the slow rate of sea level rise for the last several thousand years. Thus the area of mash has expanded as new lands lands were inundated. in the future, if sea level rises more rapidly than the land surface of the marsh, the area of marsh will contract, reversing the expansion of the last several thousand years. Where bulkheads are built just inland of the marsh to protect coastal development, wetlands may not be able to migrate inland and be totally lost..
Source: Greenhouse effect and coastal wetland Policy: How Americans could abandon an area the size of Massachusetts at minimum cost

Tidal wetlands are generally at an elevation between mean sea level and spring high water (the average high tide during new moons and full moons). So one might expect that in an estuary where spring high water is two feet above mean sea level, a two foot rise in sea level would drown all the existing tidal wetlands, while creating new tidal wetlands in the dry land that had been less than two feet above spring high water. If this occurs, a large portion of the wetlands will be lost because the land within two feet above spring high water is generally a small percentage of the area of tidal wetlands. The ratio of the area of wetlands to the area of dry land low enough to become wetland is called the topographic vulnerability of the wetlands. If part of that low land is developed and protected from the rising sea, however, the actual land available for wetland creation is less than suggested by topography alone.

Fortunately, the surface of the wetlands often rises along with the sea, because marsh grasses trap sediment and create peat. The elevation of wetland surfaces is often called "wetland accretion" (but beware: the term "wetland accretion has some other meanings as well). If the wetland surface keeps pace with the rising sea, no wetlands will drown and the area of wetlands will increase as low lands are submerged and convert to wetland. But if sea level rises too rapidly, the existing wetlands will convert to open water and the newly submerged lands will account for most of the remaing area of wetlands. Most wetlands are able to keep pace with the current rate of sea level rise, but would not be able to keep pace if sea level were to rise three feet in the next century. The figure to the right summarizes the relationship between topographic vulnerability, shore protection, and wetland accretion. Because these three sources of wetland vulnerability require three very different skill sets to assess, many studies evaluate one of these three factors in detail while making rudimentary assumptions about the others

Reports and other products

Topographic Vulnerability
Wetland Vertical Accretion
Will development and shore protection prevent wetlands from migrating inland?
General reports on wetland vulnerability to sea level rise

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