Global Climate Change and Sea Level Rise: Potential Losses of Intertidal Habitat for Shorebirds

Global warming is expected to result in an acceleration in current rates of sea level rise, inundating many low-lying coastal and intertidal areas. This could have important implications for organisms that depend on these sites, including shorebirds that rely on them for feeding habitat during their migrations and in winter. We modeled the potential changes in the extent of intertidal foraging habitat for shorebirds at five sites in the United States that currently support internationally important numbers of migrating and wintering birds. Even assuming a conservative global warming scenario of 2°°C within the next century (the most recent projections range between 1.4°°C and 5.8°°C), we project major intertidal habitat loss at four of the sites (Willapa Bay, Humboldt Bay, San Francisco Bay, and Delaware Bay). Projected losses range between 20%% and 70%% of current intertidal habitat. Such losses might jeopardize the ability of these sites to continue to support their current shorebird numbers. The most severe losses are likely to occur at sites where the coastline is unable to move inland because of steep topography or seawalls. The effects of sea level rise may be exacerbated by additional anthropogenic factors. In southern San Francisco Bay, for example, sea level rise may interact with land subsidence due to aquifer depletion, and the constraints imposed by existing seawalls on the landward migration of habitat, resulting in the greatest habitat loss. At the fifth site (Bolivar Flats) we project smaller losses as the intertidal habitats are unconstrained by sea walls and will be able to migrate inland in response to rising sea level. Installation of additional coastal protection barriers at this site and others is likely to exacerbate the rate and extent of intertidal habitat loss.