The San Francisco Bay estuary contains the largest remaining expanse of tidal salt marshes in the western U.S. These marshes are home to a variety of federal and state protected species, such as the California clapper rail, California black rail, and the salt marsh harvest mouse. The estuary is also located on the Pacific Flyway, and is an important site for migrating and wintering birds. As climate conditions change, these salt marshes face a number of threats, including accelerated rates of sea-level rise, shifting precipitation, erosion, and more frequent and intense storms. Seas in the San Francisco Bay estuary have been rising 2.2 centimeters per decade, and could rise by as much as 1.24 meters by 2100, according to some projections.
The goal of this project was to identify how marsh plant communities in the San Francisco Bay estuary might be impacted by sea-level rise through 2100. Understanding the changes in salt marsh habitat will help wildlife managers identify the possible effects on wildlife species, enabling managers to start developing adaptation strategies now. To do this, researchers collected elevation, vegetation, and water level data at 12 tidal salt marshes around the San Francisco Bay estuary between 2008 and 2011. Using this information, they predicted the rate of marsh growth (i.e. accretion) and changes in plant communities at the sites through 2100.
Results show that the effects of sea-level rise will increase threats to already vulnerable wildlife in the San Francisco Bay estuary. Although some parts of the study area are projected to maintain marsh vegetation through 2100, these areas only comprise 4 percent of the total marsh area surveyed. The remaining 96 percent of marshes in the study area are projected to transition to mudflats by 2100. In fact, most areas are projected to lose high and mid-marsh vegetation by 2050. This type of vegetation provides critical habitat to the salt marsh harvest mouse, California black rail, and nesting songbirds.
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“Salt marsh harvest mouse - Credit: M. Bias, DOI”
“Marsh - Public Domain”