part because the land is rising. In some areas, the rising land surface will help coastal marshes maintain their elevation as sea level rises, making sea-level rise a less important threat in this area than other parts of the coast. Should the highest sea-level projections for 2100 be realized, marsh survival will be possible only in areas with high local sediment supply.

A detailed assessment of the response of west coast marshes to sea-level rise is hampered by the lack of long-term and/or comparable data and by the variety of geological (e.g., vertical land motion, sediment supply), hydrological (e.g., floods, storms, dams), and biological (e.g., accumulation of organic matter) factors that govern marsh survival, all of which combine to cause significant spatial variability along the coast. In general, most marshes with natural sediment delivery and unimpaired hydrology will survive the sea levels projected by the committee for 2030 and 2050. For 2100, marshes will need room to migrate, a high sediment supply, and uplift or low subsidence to survive projected sea-level rise.



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