Vulnerability of salt marsh bird populations to sea level rise
Hunter, Elizabeth Ann
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Sea level rise (SLR) poses a substantial threat to many coastal species through inundation and fragmentation of habitat and increases in the frequency and severity of extreme high tides and storms. This dissertation comprises a vulnerability assessment for salt marsh bird species, investigating the exposure, sensitivity, and resilience of species to SLR. In Chapter 2, we found that vertebrate species that relied heavily on salt marshes (as opposed to other landcover types such as forests and freshwater marshes) would be most exposed to changes from SLR, primarily in the form of fragmentation. Given this outcome, we examined sensitivity differences between two salt marsh specialist species: Clapper Rails and Seaside Sparrows (Chapter 3). Although both of these species are salt marsh obligates, we found striking differences in their habitat preferences, which will lead to divergent responses to SLR. Clapper Rails will likely benefit from SLR in the short term; however, Seaside Sparrows will experience drastic declines in their preferred habitats of high elevation, high salinity marshes far from forests. In Chapter 4, we investigated a conservation area planning technique called “conserving nature’s stage” (CNS) that could be used to find climate change-resilient habitat for multiple species with differing responses to SLR. We found a strong relationship between environmental and species diversity, and sites chosen by CNS were also resilient to SLR. CNS thus seems to be a viable strategy for conservation site selection in salt marshes, and potentially other areas where SLR will affect environmental features. In Chapter 5, we investigated another aspect of Seaside Sparrow ecology: how their nest site selection is affected by a trade-off to avoid threats of predation and tidal inundation. We found that sparrows dealt with this trade-off by altering their habitat selection behaviors in relation to a threat’s predictability. Using an individual-based model (Chapter 6), we found that such behaviors may increase the species’ resiliency to SLR, but nest success rates could become very low under extreme SLR scenarios.