Martin et al. (2005) suggest that the structure be built: (1) as far away from shore as possible, (2) as porous as possible, (3) with as much overtopping (i.e., water flowing over the structure) as possible, (4) with maximum gap size and number, (5) without beach nourishment, (6) without lateral groins, and (7) be avoided if at all possible, in areas dominated by fine sediments. The manuscript concludes that “the number of LCS should be reduced to the minimum necessary to protect the coast, avoiding large-scale effects of habitat loss, fragmentation and community changes.” These ecological considerations have been incorporated into a model to design more environmentally friendly structures to protect shorelines from erosion (see Zanuttigh et al., 2005).

Mills Island, Chincoteague Bay, Maryland

In some locations, shoreline erosion creates habitat for ecologically important species. Shoreline stabilization in these areas would lead to loss of habitats and ecosystem services. This is the case at Mills Island, located on the western shore of Chincoteague Bay, MD, an area of high relative sea-level rise. This marsh island is eroding at a rate of half a meter (approx. 2 ft) yr−1 exposing compacted peat in the subtidal areas. This sediment is not suitable to seagrass growth, a plant type that serves as habitat for a variety of commercially and ecologically important species. As a result, marsh erosion is also leading to seagrass loss with the exception of areas where dunes located within the marsh island are also eroding (Wicks, 2005). Where the dunes are eroding, a layer of sand is deposited on top of the compacted marsh peat making it a suitable seagrass substrate. The construction of any structure to reduce or stop shoreline erosion will lead to deepening of the offshore area and will no longer allow sand to cover the unsuitable compacted marsh peat, leading to the loss of seagrass habitat (Wicks, 2005). Therefore, the benefits of shoreline erosion (e.g., sediment supply) need to be considered when developing a regional shoreline protection plan.

FINDINGS

  • A general lack of information exists about the ecosystem services provided by structures to mitigate shoreline erosion.

  • Techniques to mitigate shoreline erosion lead to the loss of some ecosystem services.

  • The loss of ecosystem services associated to the mitigation of eroding shorelines can be localized when only a few structures exist within a system but can alter the whole area (even where such structures are absent) when a certain critical percentage of shoreline modification is exceeded.

  • Techniques to mitigate shoreline erosion may contribute some ecosystem services, but not the range of services provided by natural systems.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement