Impact of climate change on seabird species off the east coast of Scotland and potential implications for environmental assessments: study

Introduction

Offshore Renewable Developments (ORDs) can make a significant contribution to the Scottish Government's target to generate 50% of overall energy consumption from renewable sources by 2030 and have decarbonised the energy system almost completely by 2045 (Scottish Government, 2022). However, the Scottish Government has a duty to ensure that ORDs are delivered in a sustainable manner, in accordance with the requirements of the Marine Strategy Framework Directive (EC/2008/56), the Habitats Directive (EC/92/43) and the Birds Directive (EC/79/409). Offshore renewable developments have the potential to affect seabirds that are protected by the EU Birds Directive, and transposed domestic legislation, notably from collisions with turbine blades and through displacement from important habitat (Drewitt & Langston 2006; Masden et al. 2010; Scottish Government 2011).

A key current concern is that assessments of ORDs on seabird populations, in particular Population Viability Analyses that forecast future population change, do not account for any potential changes to seabird populations arising from environmental change. However, there is widespread evidence that seabirds are being affected by changes in marine ecosystems as a result of climate change. Over one third of UK seabird species have experienced declines in breeding abundance of 20-30% or more since the early 1990s (Mitchell et al. 2018) and 6 of the 25 UK breeding seabird species are Red-listed (Eaton et al. 2015). Climate change is considered to be one of the primary causes of these declines (Daunt & Mitchell 2013; McDonald et al. 2015; Carroll et al. 2015; Daunt et al. 2017, Dias 2019, Daunt & Mitchell 2020). Climate change can affect seabird populations via two main processes: indirect effects via changes in food supply, and direct effects such as mortality from extreme weather. These effects could interact with the effects of ORDs additively, synergistically or antagonistically (Crain et al. 2008; Burthe et al. 2014). Factoring in these processes to assessments is therefore critically important in improving estimates of the effects of ORDs on future population change in protected seabird populations (Daunt et al. 2017, Daunt & Mitchell 2020).

In this project, we examined the potential impacts of climate change on Scottish seabirds breeding on the eastern seaboard by exploring relationships between climate and seabird behaviour, demographics, abundance and distribution. We developed future estimates for seabird distribution and demography using a scenario (SRES A1B) of future emissions from the UKCP09 climate projections (2018), and hence climate. Under this scenario, we used statistical models to produce projections of:

i. The spatial distribution of seabird foraging areas;

ii. Overall species seasonal abundance based on density maps of seabirds at sea;

iii. Demographic rates at seabird breeding colonies (productivity and adult survival);

iv. Demographic rates achieved under varying foraging ranges at seabird breeding colonies;

We compared these future projections against the current "baseline" values for key population and distribution characteristics to estimate the likely impacts of climate change, analysed in a way that accounts for uncertainty. Finally, we discuss the implications of our findings for offshore wind assessments.