Modeling Sea-Level Rise in San Francisco Bay Estuary: Executive Summary and Final Report

The International Panel on Climate Change has identified coastal ecosystems as areas that
will be disproportionally affected by climate change. Current sea-level rise projections range
widely with 0.57 to 1.9 meters increase in mea sea level by 2100. The expected accelerated rate
of sea-level rise through the 21st century will put many coastal ecosystems at risk, especially
those in topographically low-gradient areas.
We assessed marsh accretion and plant community state changes through 2100 at 12 tidal
salt marshes around San Francisco Bay estuary with a sea-level rise response model. Detailed
ground elevation, vegetation, and water level data were collected at all sites between 2008 and
2011 and used as model inputs. Sediment cores (taken by Callaway and others, 2012) at four
sites around San Francisco Bay estuary were used to estimate accretion rates. A modification of
the Callaway and others (1996) model, the Wetland Accretion Rate Model for Ecosystem
Resilience (WARMER), was utilized to run sea-level rise response models for all sites. With a
mean sea level rise of 1.24 m by 2100, WARMER projected that the vast majority, 95.8 percent
(1,942 hectares), of marsh area in our study will lose marsh plant communities by 2100 and to
transition to a relative elevation range consistent with mudflat habitat. Three marshes were
projected to maintain marsh vegetation to 2100, but they only composed 4.2 percent (85
hectares) of the total marsh area surveyed.