Mangrove Areas in the United States Likely to Be Submerged by Projected Sea Level Rise: Declines in Areal Extent, Carbon Sequestration, And Ecosystem Services

Sea level rise (SLR) threatens coastal ecosystems, which
are critical
for sequestering carbon (C), providing habitat, and reducing storm
surge. Mangrove forests are particularly efficient in C sequestration
and host a variety of dependent species. Using United States (U.S.)
National Oceanic Atmospheric Administration data, we estimated future
mangrove inundation from SLR at 0.3, 0.61, and 3.0 m in the U.S. By
3.0 m of SLR (around the middle of next century), we estimate mangrove
area loss to be almost half of current areas, or 47.4% of the approximately
266.7 thousand ha currently present. To estimate C sequestration and
ecosystem service loss, we compared scenarios where inundated mangrove
areas convert to saltmarsh vs open ocean. We estimate sequestration
loss to be approximately 30–199 thousand metric tons C y–1 from 3.0 m of SLR. Combined with decreases in other
ecosystem services, this represents an annual loss of $5.8 billion
(in USD and Int$) per meter of SLR. Migration poleward, although unlikely
in areas with coastal development, may reduce some impacts in select
locations. Overall, we conclude mangrove areas and their accompanying
ecosystem services are likely to be greatly reduced by SLR in the
future.