Coupled impacts of sea-level rise and tidal marsh restoration on endangered California clapper rail

We develop a predictive multi-process framework to quantitatively assess the spatially variable, interlinked dynamics of sea-level rise, wetland transition, habitat suitability and connectivity, and shorebird distribution and abundance. Bird behavior is represented in a spatially explicit agent-based model that tracks responses of individuals to predicted changes in local habitat quantity and quality. We apply this framework to the endangered California clapper rail (Rallus longirostris obsoletus) in the San Francisco Estuary, US, under a range of sea-level rise and conservation scenarios aimed at clapper rail recovery. The framework enables quantification of the relationship between critical habitat destruction and clapper rail population decline. The most influential factors that characterize the quality of tidal marsh habitat are salinity, which is a proxy for higher quality nesting environment and abundance of macroinvertebrates, and tidal conditions, which affect flood and predation threats. Results suggest that clapper rail viability should remain at the present level for moderate sea level rise. However, for a rise of 1.66 m, extinction risk increases from 0.01 to 0.36. The framework enables quantitative evaluation of proposed conservation efforts, and should complement existing theory and empirical inferences. Compared with sub-regional efforts, estuary-wide conservation is more effective in improving reproduction and dispersal success and accommodates a sea-level rise of an additional ∼10 cm before population falls below criticality. Should sea level rise to the predicted maximum, proposed conservation efforts are likely to be ineffective in preventing California clapper rail extinction by 2100.