Resilience of U.S. coastal wetlands to accelerating sea level rise
Abstract
Coastal wetlands provide a wide array of ecosystem services, valued at
trillions of dollars per year globally. Although accelerating sea level
rise (SLR) poses the long-term threat of inundation to coastal areas,
wetlands may be sustained in two ways: by positive net surface-elevation
change (SEC) from sediment and organic matter buildup and by
accommodation, or horizontal migration into refugia—low-lying,
undeveloped upland areas that become inundated. Using a simple model
together with high-resolution elevation data, we provide, across the
contiguous United States, analysis of the local effects of SLR, maximum
SEC rates, and coastal development on the long-term resilience of
coastal wetlands. We find that protecting current refugia is a critical
factor for retaining wetlands under accelerating SLR. If refugia are
conserved under an optimistic scenario (a high universal maximum SEC
rate of 8mm/yr and low greenhouse gas emissions), wetlands may increase
by 25.0% (29.4%−21.5%; 50th, 5th−95th percentiles of SLR) by the end
of the century. However, if refugia are developed under a more
pessimistic scenario (a low universal maximum SEC rate of 3mm/yr, high
greenhouse gas emissions, and projections incorporating high ice-sheet
contributions to SLR), wetlands may decrease by -97.0%
(-82.3%−-99.9%). These median changes in wetland area could result in
an annual gain of ∼$222 billion compared to an annual loss of ∼$732
billion in ecosystem services in the US alone. Focusing on key
management options for sustaining wetlands, we highlight areas at risk
of losing wetlands and identify the benefits possible from conserving
refugia or managing SEC rates.