Transient coastal landscapes: Rising sea level threatens salt marshes

Area of Science:

• Coastal ecology
• Environmental science
• Geomorphology

Background:

• Salt marshes provide critical ecosystem services.
• Accelerated global sea level rise (SLR) threatens salt marsh survival.
• Previous survival estimates relied on sea level rise to marsh accretion ratios.

Purpose of the Study:

• To provide an empirical estimate of salt marsh habitat loss using long-term, spatially detailed measurements.
• To assess the impact of increased submergence and coastal erosion on salt marsh ecosystems.
• To project the future viability of salt marshes under current and anticipated SLR rates.

Main Methods:

• Long-term (1979-2015) monitoring of a New England salt marsh.
• Spatially detailed comparison of habitat changes.
• Meta-analysis of existing salt marsh data.

Main Results:

• Observed prominent changes in the marsh's habitat mosaic.
• Habitat changes were consistent with increased submergence and coastal erosion.
• Model projections indicate potential salt marsh ecosystem disappearance by the early next century.

Conclusions:

• Current rates of SLR, marsh accretion, and habitat loss, coupled with coastal squeeze, threaten salt marsh survival.
• Empirical data suggest many salt marshes globally may face submergence.
• 40-95% of global salt marshes could be submerged by century's end, depending on SLR rates.