Julian K. Wood | Search USGS

USGS2018

Rising tides: Assessing habitat vulnerability for an endangered salt marsh-dependent species with sea-level rise

Salt marsh-dependent species are vulnerable to impacts of sea-level rise (SLR). Site-specific differences in ecogeomorphic processes result in different SLR vulnerabilities. SLR impacts to Ridgway’s rail ( Rallus obsoletus ) of Southern California (SC) and San Francisco Bay (SF), U.S.A. could foreshadow SLR effects on other coastal endemic species. Salt marsh vulnerabilities to SLR were forecasted across 14 study sites using the Wetland Accretion Rate Model of Ecosystem Resilience, which accounts for changes in above and belowground marsh processes. Changes in suitable habitat for rail were projected with MaxEnt. Under a high (166 cm/100 yr) SLR scenario, current extent of suitable habitat is projected to increase by 34% across the combined area of 14 sites by 2050, but by 2100, total habitat suitability is projected to decrease by 83%, with six salt marshes losing over 95% of suitable habitat. Under a high SLR scenario, SF’s suitable habitat is predicted to increase by 35% at mid-century, and SC’s current suitable habitat extent will increase by 24%. However, by 2100, SF is forecasted to lose 84% of suitable habitat and SC to lose 80% of its current habitat extent. If accretion rates cannot keep pace with SLR, salt marsh obligate species are in danger of being extirpated from their habitat.

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USGS2016

Endangered species management and ecosystem restoration: Finding the common ground

Management actions to protect endangered species and conserve ecosystem function may not always be in precise alignment. Efforts to recover the California Ridgway’s Rail ( Rallus obsoletus obsoletus ; hereafter, California rail), a federally and state-listed species, and restoration of tidal marsh ecosystems in the San Francisco Bay estuary provide a prime example of habitat restoration that has conflicted with species conservation. On the brink of extinction from habitat loss and degradation, and non-native predators in the 1990s, California rail populations responded positively to introduction of a non-native plant, Atlantic cordgrass ( Spartina alterniflora ). California rail populations were in substantial decline when the non-native Spartina was initially introduced as part of efforts to recover tidal marshes. Subsequent hybridization with the native Pacific cordgrass ( Spartina foliosa ) boosted California rail populations by providing greater cover and increased habitat area. The hybrid cordgrass ( S. alterniflora × S. foliosa ) readily invaded tidal mudflats and channels, and both crowded out native tidal marsh plants and increased sediment accretion in the marsh plain. This resulted in modification of tidal marsh geomorphology, hydrology, productivity, and species composition. Our results show that denser California rail populations occur in invasive Spartina than in native Spartina in San Francisco Bay. Herbicide treatment between 2005 and 2012 removed invasive Spartina from open intertidal mud and preserved foraging habitat for shorebirds. However, removal of invasive Spartina caused substantial decreases in California rail populations. Unknown facets of California rail ecology, undesirable interim stages of tidal marsh restoration, and competing management objectives among stakeholders resulted in management planning for endangered species or ecosystem restoration that favored one goal over the other. We have examined this perceived conflict and propose strategies for moderating harmful effects of restoration while meeting the needs of both endangered species and the imperiled native marsh ecosystem.

California↗