Sea level rise and coastal hazards are putting human and natural communities along the coasts at greater risk than ever.
Tidal Marshes
Among the most productive ecosystems on Earth, tidal wetlands perform many functions that are highly valued by society, called "ecosystem services." Wetlands protect coastal water quality by filtering land-derived nutrients and contaminants; they are an important component of the coastal food web; they provide valuable wildlife habitat; and they protect upland and shoreline areas from flooding and erosion associated with storms. In sum, wetlands support the health of our coastal ecosystem and the recreational and economic activities that depend on it.
As the sea rises, wetlands must grow – both vertically and horizontally – or risk being drowned in place. In order to grow vertically, a wetland accumulates sediment on its surface. If this rate of accretion is greater than the combined effects of sea level rise and subsurface compaction, the marsh keeps its head above water. In New York, most of the marshes that have been studied appear to be in balance with current rates of sea-level rise. Several things could change this, however. First, because sea level rise is accelerating, marshes will have to accrete sediment even faster to keep up. Second, any reduction in the amount of sediment available for accretion (because of natural or man-made impacts) increases the risk of submergence.
In order to grow horizontally, wetlands require adjacent space into which to migrate. New York's tidal wetlands themselves are well protected by federal, state, and local law, but the areas adjacent to many of these wetlands are already developed. Without additional protection of adjacent areas, property owners adjacent to marshes might fortify their property as sea level rises to prevent inundation of their property. But this action closes off a migration pathway for the wetland, leaving it nowhere to go.
Despite regulatory protection, it is clear that salt marshes are already losing acreage, and shifting from high marsh to low marsh species composition, probably due to a combination of factors including sea level rise. Salt marshes in New York City's Jamaica Bay are undergoing rapid conversion from vegetated wetland to mudflats, with sea level rise identified as one of several contributing factors. Accelerating sea level rise will only exacerbate these losses, and we will lose the associated ecosystem services these important areas provide.
Tidal marshes can be mapped on a base layer included in the mapping tool on this site. Two marsh-related parameters can also be mapped: Potential Population Protection and Potential Viability. Potential Population Protection
