AUG 15, 2016 JORDAN ROSENCRANZ
When I tell people that I study the vulnerability of salt marshes to sea-level rise in California, the typical responses are “What’s a salt marsh?” or “We have those in California?”. Because most of California’s salt marshes are small, and isolated by development and topography, these questions don’t surprise me. Instead, these questions serve as motivation because it worries me that future generations may only hear the clappering call of my favorite salt marsh bird, the endangered Ridgway’s Rail (Photo 2), in a zoo or as a recording.
I encourage fellow Californians as they drive along the coast to stop and notice how the pickleweed shrubs poke out above the high tides at Upper Newport Bay, or how the tidal creeks at Corte Madera marsh, wander through green swaths of cordgrass (Figure 1).
These roadside salt marshes may seem humble because they don’t awe you like the redwood forests of California, or impress you like the waves of the Pacific Ocean. Still, these Pacific coast salt marshes protect secretive birds and mammals that live at the intersection of land and sea. Compared to the vast monocultures of cordgrass that dominate on the Atlantic and Gulf Coasts of North America, salt marshes of California have a shrub-dominated marsh plain containing interesting native plants, such as alkali heath, fleshy jaumea, and pickleweed, with cordgrass found near the edges of tidal creeks (Photo 3).
Before I began my master’s work in 2010, I admit I also tended to overlook these marsh ecosystems. However, a chance to engage in salt marsh field work as a graduate student changed my perspective. My first visits to Mugu Lagoon and Seal Beach wetlands in California were welcomed escapes from classes at UCLA, but after a few years of research, I also started to understand more fully the characteristics that made these ecosystems unique and highly vulnerable to the effects of climate change and sea-level rise. During a visit in October 2015, a USGS field technician and I were collecting water samples to monitor sea-level rise vulnerability and assess potential impacts of a sea-level rise adaptation strategy. Interestingly, the tides were 6 inches to 1 foot higher than predicted due to El Nino effects, and the temperatures were expected to break 100 degrees – conditions that could be the norm if temperatures track regional climate change and sea-level rise projections. I too began to contribute to the detailed scientific understanding of the sedimentary dynamics of the salt marsh system through my research on sediment fluxes at Seal Beach and Mugu Lagoon.
As wetland scientists, we are simultaneously trying to understand the effects of climate change and sea-level rise on salt marshes, and also trying to the make them more resilient to such forces. Salt marshes could be the first coastal ecosystems to perish in the wake of climate change and sea-level rise, or they can be a success story of adaptation. In the field, we monitor current and historic accretion rates using soil cores and surface elevation tables to understand how salt marshes respond vertically to sea-level rise changes. We also estimate current elevations with centimeter level accuracy, allowing us to downscale marsh elevation scenarios that are more relevant for individual Rails, and track sediment fluxes (Photo 4) to determine how the salt marshes and tide channels might evolve.
Recent habitat suitability projections for 14 individual salt marsh sites in the San Francisco Bay Area and Southern California show that 90% of the current breeding habitat for two coastal Ridgway’s Rail sub-species could be lost by 2110 under a sea-level rise rate of 1.66m/100yr. While salt marshes like Laumeister in the South Bay of San Francisco Bay Area may have adequate sediment supply and elevation capital to keep pace with local sea-level projections, low elevation salt marshes with urbanized watersheds like Seal Beach wetlands may be on the brink of collapse. Conservation of breeding season habitat for salt marsh obligate species, like Ridgway’s Rails, in the face of sea-level rise may involve short-term strategies, such as deploying nesting platforms, and long term measures, such as adding sediment to the marsh plain. While we expect the loss of breeding habitat to have catastrophic effects on the species in the long term, loss of high tide refuge habitat in the near term, due to coastal squeeze, may only speed up these predicted extirpations. Thus, if we want future generations to be able to hear the call of the rail in the wild, the time to plan adapt is now!
Jordan Rosencranz is a Southwest CSC Fellow and further affiliated with the Environmental Science and Engineering Program at UCLA as well as the USGS Western Ecological Research Center at the San Fransisco Bay Estuary Field Station. His research interests include monitoring the vulnerability coastal wildlife species and habitats to climate change and sea-level rise, and understanding the effectiveness of different sea-level rise and climate change adaptation strategies.
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