Wind and waterbirds: Establishing sustainable mortality limits within the Atlantic Flyway
In recent years, offshore wind development has become one of the fastest growing energy sectors in the world and the focus of the clean energy movement in the United States. The Atlantic Coast offers shallow, near-shore water5 in close proximity to large load centers with some of the most lucrative and rapidly expanding energy markets in the count ry. Wind energy along the Atlantic Coast is projected to become a 170 billion dollar industry that could significantly reduce dependency on fossil fuels. All coastal states north of South Carolina support wind development and have adopted Renewable Portfolio Standards that include an estimated 54,000 megawatts of offshore energy by 2025. To meet these collective policies with current turbine technology would require the deployment of 10-20,000 turbines in waters with less than 30-m depth over the next 15 years. The Atlantic Flyway supports one of the largest near shore movement corridors of birds in the world including many declining species of conservation concern. Much of the bird activity along the flyway occurs within a thin veneer along the coastline. Birds funnel through the flyway from a broad geographic area and their relationships to the Atlantic Coast are diverse. In addition to using the coastline as a movement corridor, many species use portions of the Atlantic Coast as migratory staging areas, breeding grounds or wintering grounds. Of particular conservation significance are taxonomic forms or populations that depend exclusively on the Atlantic Coast for some portion of their life cycle. Build out of the wind industry along the Atla1tic Coast will result in the largest network of overwater hazards ever constructed, adding another layer of mortality to many populations that are contending with a list of human-induced sources of mortality. From a population perspective, the central question is not how many individuals are killed annually but if the focal population is able to sustain the mortality incurred and still reach management objectives. Mortality is a cumulative factor in population regulation and defining limits on human-induced mortality is a critical component of management decisions. This report uses a form of harvest theory referred to as Potential Biological Removal (PBR) to develop a population framework for estimating sustainable limits on human-induced mortality. The approach is appropriately precautionary in using minimum population estimates and a graded recovery factor designed to allow for species recovery. The approach has the benefit of requiring relatively few demographic parameters. Enough information was available from the literature for 46 nongame waterbird species to allow for estimates of sustainable mortality limits (from all human-caused sources). Several populations stood out as having particularly low mortality limits including the Atlantic breeding populations of roseate tern, piping plover, and American oystercatcher, the Hudson Bay population of marbled godwit that winters along the south Atlantic, the rufa form of the red knot that uses the Atlantic Coast as a staging area during migration, and the estimated population of common loons wintering along the Atlantic Coast . Several other species for which demographic estimates are not currently available are also likely vulnerable to elevated mortality.