Accelerated sea level rise presents a new challenge to the conservation of sensitive coastal habitats already impacted by human activities and populations focused along the coast. We developed a novel assessment of the vulnerability of habitats to sea level rise which provides spatially explicit quantifications of sea level rise conservation strategies. We applied this approach to the entire California coast because it harbors high biodiversity, high endemism, 26.5 million people, and the 6th largest global economy, however, the approach can be applied more broadly. Within each of 5,631 1km2 analytic units we characterized the landscape into 22 wetland and 18 upland habitats, and 17 built environment classes. We assessed the vulnerability of 40 habitats to 1.5m of sea level rise by quantifying the sensitivity and spatial extent of exposure of each habitat patch to intertidal and subtidal waters, relative to the area available for each patch to transgress inland in response to rising seas. By combining habitat vulnerability with conservation management status, we inform strategies to conserve habitats in the face of sea level rise including: conserving resilient strongholds, managing in place for resilience, and mitigating potential losses by adapting the built environment or conserving and restoring future potential habitat.
Results/Conclusions
A majority of the area of several key coastal habitats, including beaches, rocky intertidal, and estuarine marshes are highly vulnerable. Results show in California there is as much resilient un-conserved habitat as there is resilient conserved habitat providing opportunity to invest in resilient conservation, and indicating that core strategies still apply. We identified opportunities to manage habitats in place for resilience, a strategy that will be important for habitats such as estuarine marshes. We determined that conserving minimally developed lands today for their future potential habitat value is critical to maintaining coastal habitat extent and function. Only a small proportion of coastal agriculture, itself projected to be come intertidally inundated, could collectively provide 200 km2 of habitat transgression area. In more urban settings, considering habitat resilience in coastal infrastructure adaptation decisions will be important. Such adaptation will yield dividends, both through increased resilience of the built environment, as well as through the protective services and many other co-benefits provided by resilient coastal habitats. We determined that significant investment in each strategy will be necessary to maintain coastal habitats in California, a likely universal pattern. Our approach is parsimonious and modular, enabling it’s use in other coastal settings around the world.