Seabirds: strategic ornithological compensatory measures: review

Executive Summary

Due to the complex nature and variety of table design in this document we have provided a single Excel file of all the material.

1. The Scottish Government have set out goals for significant offshore wind capacity to be developed as part of their Net Zero policies. The scale of proposed and planned development has the potential to adversely affect seabird populations protected under the Habitats Regulations. Should developments or plans proceed where adverse effects are concluded, there is an obligation to deliver compensatory measures to offset for impacts. Recent policy and legislative changes mean that, in future, compensation could be delivered strategically across multiple offshore wind projects.

2. To ensure that strategic compensatory measures can be delivered effectively and with maximum positive benefit to seabirds, there is a need to assess which measures have ecological and practical feasibility within Scotland. The Scottish Government scoped out a list of potential measures which were evaluated in this project. The project was structured around two work packages which assessed the proposed measures; the first to evaluate their ecological feasibility and the second to evaluate their practical feasibility.

3. For each proposed measure, we identified corresponding conservation actions. The term ‘compensatory measure’ is a broad term which could include either a single or a suite of coordinated actions that must deliver a compensatory response, i.e. counteracting a given population level impact. Here, we use a more specific term, ‘conservation action’, which refers to management interventions that have potential to lead to population level gains and/or recovery for a seabird species (e.g. by improving productivity or survival). Consequently, conservation actions have potential to be used as compensatory measures subject to meeting various tests, both relating to efficacy and other factors such as additionality.

4. Measures that corresponded to clear conservation actions were assessed through a systematic literature review process and evaluated on their ecological feasibility, using a qualitative approach, and enabling the comparison of their relative ecological feasibility. Where conservation actions were not readily identifiable from the initial proposed measures, scoping reviews were conducted to identify and evaluate potential conservation actions. Additionally, bycatch mitigation was explored through a targeted review.

5. The conservation actions with the highest ecological feasibility scores (a composite score including ecological effect and accounting for strength of the evidence base) were, in descending order: Mammalian predator eradication and/or management, End of the Gannet harvest at Sula Sgeir; Avian predator management; Fishery closure or enhanced management of prey fisheries; Reduction of disturbance (at sea); Reduction of disturbance (at colony); and Sandeel fishery closure. All conservation actions were assessed for their practical feasibility, excluding Reduction of disturbance (at sea). The latter was excluded due to there being a consensus that, at this time, there is insufficient evidence to have confidence that this action could lead to a meaningful scale of compensation.

6. For measures assessed via scoping and targeted reviews, we identify a list of potential conservation actions and provide a high-level state-of-the-art review that considers key relevant recent papers and reports. Measures include: Management of supporting habitats; Reducing disease spread; Habitat management; Changes in large gull management; and Bycatch mitigation in longline fisheries. The last measure was also included for the practical feasibility assessments.

7. Practical feasibility assessments included: identifying the steps required to implement each action; ecological benefits anticipated in Scotland for the different seabird species and other wildlife; research and monitoring recommendations; and key considerations including barriers and potential solutions to these.

8. Sandeel fishery closure and fishery closure or enhanced management of prey fisheries had medium levels of ecological efficacy and low–medium overall feasibility scoring. Both actions can indirectly benefit seabirds through an increase in prey availability. However, quantifying the impact and benefit is challenging as prey fish are limited by other non-fishery factors as well. They should both be considered as a measure to enhance ecosystem resilience. Key considerations include international aspects, potential socio-economic impacts, and potential for displacement.

9. The end of the Gannet harvest at Sula Sgeir had a low–medium level of ecological efficacy and a low–medium overall feasibility scoring. It also proved to be the conservation action were there was lowest uncertainty of its benefits. Benefits will likely be stronger for the North Rona and Sula Sgeir SPA colonies. However, limited benefit is expected to Gannet populations more widely in Scotland, though this is yet to be fully understood. This action would require local community cooperation for its implementation, which may be challenging given its cultural heritage to the Ness community.

10. Mammalian predator eradication and/or management had a medium level of ecological efficacy and a high overall feasibility scoring. A key issue for this action is the requirement for biosecurity in perpetuity, leading to an ongoing long-term commitment for its continued success. Avian predator management, on the other hand, had a low–medium level of ecological efficacy and a low overall feasibility score. The low score mainly reflects the high uncertainty and paucity of evidence regarding its potential benefit for seabirds and that this is highly context-specific depending on the specific management intervention and the location. This action is relatively low-cost but may not be scalable, limiting its application for strategic compensation.

11. Reducing disturbance at colonies had a medium level of ecological efficacy and a low–medium overall feasibility scoring. Seabirds at colonies can be disturbed by on-land activities, by sea, or via Unmanned Aerial Vehicles (UAVs) and management will need to be conducted accordingly. A key consideration with this action is that there are already existing laws and guidance for minimising disturbance on wildlife, especially at SPAs, so additionality issues would need considering.

12. Bycatch mitigation in longline fisheries had a medium level of ecological efficacy and a medium overall feasibility scoring. This action would likely require international coordination to deliver. Quantifying overall population level benefits, as well as apportioning benefits to individual SPAs, is not possible with high confidence due to wide confidence intervals around bycatch rates (arising from currently low monitoring effort) and difficulty linking bycaught birds to specific SPAs.

13. Conservation actions varied with regards to their application, benefits to different seabird species, monitoring strategies, key considerations, and evidence regarding their ecological feasibility. Actions ranged from broad-scale interventions, affecting extensive areas and regions, to targeted actions implemented at one or more sites. Moreover, some actions benefited species directly, while others were some steps removed from providing a population level response. For conservation actions acting more indirectly, it is hard to quantify population-level responses, meaning that uncertainty is often high. Therefore, comparisons between actions should be taken with caution.

14. An overall qualitative assessment of the practical feasibility for seven conservation actions were produced. Ranked from least to most feasible (in the context of strategic compensation): Avian predator management (low); Reduction of disturbance at seabird colonies (low); End of the Gannet harvest at Sula Sgeir (low–medium); Sandeel fishery closure (low–medium); Fishery closure or enhanced management of prey fisheries (low–medium); Bycatch mitigation of longline fisheries (medium); and Mammalian predator eradication and/or management (high). It should be noted, however, that the overall assessment score is highly dependent on how component criteria are weighted. Additionally, significant uncertainties remain for some actions and, therefore, evaluations may change in the future as more evidence becomes available.

15. Several general recommendations are provided, these include: developing guidance for how strategic compensation measures should be evaluated; developing a framework for evaluating more indirect measures where it is technically challenging to relate these to seabird population responses; work to scope out additional compensation options for categories of potential compensation that are least developed; and developing an integrative approach to compensatory measures that accounts for, and works to support, adaptation in seabird populations to the impacts of climate change.