Building quantitative resources using PVA to assess the responses of UK seabirds to extrinsic threats

•1. Seabird populations are exposed to a wide range of threats from anthropogenic activity, and many species are rapidly declining. For decision‐makers and practitioners to give advice on the impacts of human activities and design of mitigation or compensation strategies, understanding how impacts to key demographic rates influence population dynamics and trajectories across different species is essential. Importantly, practitioners must do so in the context of the resources and information that are available to them.
•2. In this study, we build a quantitative resource using population viability analysis (PVA) that allows comparative assessment of resultant population outcomes following a wide range of impacts to breeding success and survival. We project population responses at different sizes and under varying density‐dependent regulation scenarios using a commonly utilised impact assessment tool. We examine positive and negative impact scenarios, with a view to quantifying the effectiveness of theoretical management measures. We use five UK seabird species representing a range of life‐history strategies.
•3. By running over 100,000 population models testing the responses of five seabird species to a variety of impact scenarios, we present a wide range of population projections in response to impacted seabird demographic rates. Broadly, we find that species differ as expected in sensitivity to changes in breeding success and survival according to their life‐history strategies. We demonstrate the importance, within and between species, of including density‐dependent regulation in population dynamics, even within a simple comparative resource such as this. Finally, we show population responses to interactions between degree and duration of impact to demographic rates, although we found little interspecific variation here.
•4. Practical implications . We provide a comprehensive and valuable resource that could help inform decisions around development planning and consenting. This resource allows practitioners and users to readily consider quantitative scales of impact for various ‘realistic’ scenarios when making preliminary assessments of potential impacts of new developments on seabirds, without necessarily performing detailed quantitative population modelling, while incorporating critical processes such as density dependence. It could also inform the design and evaluation of potential interventions as part of strategic compensation and wider conservation measures to sustain declining populations.