THE ABILITY OF TIDAL MARSHES TO MAINTAIN VERTEBRATE BIODIVERSITY IS SLIPPING; IS HUMAN MITIGATION POSSIBLE?

One of the services provided by salt marshes is their support of a unique assemblage of species specialized for life on the interface between terrestrial and marine environments. North America possesses the majority of the world’s vertebrate salt-marsh specialists, but the taxa in these coastal habitats are at extreme risk of extinction due to current sea-level rise. The saltmarsh sparrow, Ammodramus caudacutus, of the northeastern United States is a representative tidal marsh endemic in many ways. High tide flooding is the main cause of breeding failure, and breeding habitat is limited to marsh areas that are flooded only during spring tides, despite a suite of adaptations to withstand tidal flooding. Using nesting data from 35 tidal cycles (2002-09), we estimated the relationship between peak tide height and nest success to predict the conditions necessary for complete reproductive failure. Combined with sea-level rise projections, our results suggest this population will become inviable within 30-60 years. Additionally, habitat trajectories for the core of the species’ range indicate that 70-90% of appropriate nesting habitat will be lost by 2100. Other tidal-marsh nesting birds will face a similar fate, albeit not quite so rapidly. Available management options to protect this suite of species will require major changes in the nature of coastal zone management in the northeastern US that include rethinking current approaches to marsh restoration, the protection of alternative coastal habitats, and whether some species can really be saved.