Assessment of land-based threats to Atlantic Seabirds

Highly mobile seabirds are exposed to numerous threats during their life-cycle. During their breeding season, they face land-based threats - such as invasive alien species, diseases, or light pollution - that can result in strong population declines. Here we assess the timing, scope, and severity of land-based threats to seabird populations of petrels, albatrosses, storm-petrels and alcids in the Atlantic Ocean, in order to guide priorities for the conservation of their breeding areas, which are mostly located on islands. By combining our own field expertise of these species with a literature review, we built a dataset characterising each of 18 threats for 49 species (143 populations) across 38 Large Marine Ecosystems (LMEs). We then quantified the impact of each threat as the estimated population loss it has caused, highlighting the most impactful threats, the most impacted species and populations, and the most impacted LMEs. Invasive alien species account for the greatest population losses among the studied species, with the most impacted LMEs in island systems such as Bermuda and the Canary Current. Addressing invasive alien species in Tristan da Cunha & Gough is the single intervention with the greatest potential for population recovery. Our results support seabird conservation efforts by highlighting priorities for targeted management action.