Coastal Ecosystem Response to Sea-level Rise

Science Center Objects

USGS WERC’s Dr. Karen Thorne, her team of reseachers, and her partners are currently taking a local site network approach to describe current and future conditions and projected responses of coastal ecosystems to sea-level rise and other stressors. The Coastal Ecosystem Response to Climate Change (CERCC) program’s goal is to understand how ecosystems vary in their ability to keep up with sea-level rise. Our goal for this ongoing research is to provide scientific support and information to resource and land managers for future planning and conservation of coastal ecosystems and their natural resources as these ecosystems respond to sea-level rise. 

WERC Scientist conducting elevation surveys in a salt marsh
WERC scientist conducting elevation surveys in salt marsh (Credit: Karen Thorne, USGS WERC. Public domain.)

Modeling Wetland Response to Sea-level Rise on the Pacific Coast

To gather reliable estimates of sea-level rise impacts at regional scales, scientists at WERC and partners are using local physical and biological data to assess changes to nearshore ecosystems. WERC members and University partners have collected information from 18 coastal wetland sites in Washington, Oregon, and California with the focus on collecting high-quality field data at local wetland site scales, and then using that data to provide information that may be interpreted across the entire latitudinal gradient of the Pacific Coast.

In addition to our extensive network of sites, three estuaries in California have been intensely surveyed and metered to represent Mediterranean and northern Oceanic climate regimes (San Diego Bay, San Francisco Bay, and Humboldt Bay respectively). At all sites we examine potential sea-level rise effects and vulnerability of nearshore habitats and their dependent endangered wildlife. Using local habitat information, we develop approaches for investigating the complexity of climate and physical and biological changes to wetland ecosystems, both at scales relevant to land managers, as well as a broader Pacific coast perspective for conservation and management.

WERC Black Rail in marsh
Black rail in marsh (Public domain.)

Fate of Endangered Species in Southern California and San Francisco Bay Tidal Marshes with Sea-level Rise

Much of the California coastline is fragmented and modified, including the San Francisco Bay estuary and southern California estuaries, but these remaining areas represents the largest extent of tidal marsh in the western United States. Projected sea-level rise poses further threats to several endemic protected tidal marsh species such as the salt marsh harvest mouse, California Ridgway’s clapper rail, light-footed Ridgway’s rail, Belding’s savannah sparrow, and California black rail that are listed as federally endangered or state threatened species. Resource and land managers charged with the protection of endangered species and their habitats are in need of site-specific predictions of anticipated sea-level rise impacts through the synthesis of downscaled regional sea-level rise models and available data on species’ ecological constraints. Changing sediment loads, extreme tide and storm events, salinities, and sea-level rise will affect tidal marshes by altering the plant community composition and structure that provide the critical habitat for these endemic species.

 

Wetland Sustainability Modeling 

WERC SET reading Rush Ranch
WERC scientists use a Sediment Elevation Table (SET) at Rush Ranch to measure changes in marsh surface elevation. (Public domain.)

We have been working to improve the performance of ecosystem response modeling, including and WARMER (Wetland Accretion Rate Model for Ecosystem Resilience) for Pacific coast estuaries.  We have added mechanisms to allow close calibration to soil core characteristics and added greater flexibility in the organic matter accumulation subroutine.  We have also added the capacity to allow input of suspended sediment concentrations and information from Surface Elevation Tables (SETs).  WARMER 2.0 runs as an R script, a much needed update from the original Fortran code, allowing us to quickly analyze the results and produce figures.  The model is being adapted for mangrove ecosystems and dynamic tidal lagoons.

Rocky Shorelines and Sea-level Rise

Much of the scenic coastline includes cliff and offshore rocky islands which are vulnerable to changing ocean conditions.  These areas have both cultural and biological significance and are home to nesting seabirds and pinnipeds.  To assess the impacts of offshore rocky habitats to sea-level rise we are building a comprehensive modeling approach to integrate both biological and physical information to develop vulnerability models to inform management of these areas.

Objectives:

  • Downscale physical processes and climate projections to local scales to model with WARMER
  • Measure morphological and ecological characteristics across the habitat continuum of tidal marsh, intertidal mud flat, and subtidal shoals
  • Model wildlife habitats and native species response from sea-level rise
  • Examine spatial variability of sea-level rise vulnerability along a coastal latitudinal gradient