Seabird abundances projected to decline in response to climate change in Britain and Ireland
Author(s): Davies, J.G., Humphreys, E.M., Evans, T., Howells, R., O’Hara-Murray, R. & Pearce-Higgins, J.W.
Published: December 2023
Journal: Marine Ecology Progress Series
Digital Identifier No. (DOI): 10.3354/meps14462
In this study, a team of scientists led by BTO sought to predict the abundance of seabird species in Britain and Ireland in 2050, under climate change scenario RCP8.5 (where global temperatures rise by 2.6–4.8°C above pre-industrial levels by 2081–2100). To do this, the study’s authors attempted to estimate the relationships between seabird abundance and/or presence, and various factors to do with the ocean and climate (e.g. air temperature, precipitation, sea surface temperature) for each of 25 species. The authors then used those relationships to predict each species’ abundance in the expected climate of 2050.
These relationships were often difficult to identify, because spatial variation in seabird abundance is determined by many factors beyond climate and oceanography; for example, colonial nesting and the distribution of prey and predators. For this and additional reasons, the study’s predictions of future seabird abundance come with considerable uncertainty attached.
Of the 15 seabird species for which the study was able to make predictions, 10 were predicted to decline in abundance under this climate change scenario. Some of these declines could be considerable: the results predicted with high confidence that Fulmar, Puffin and Arctic Tern will decline by more than 70% by 2050. The declines in seabird abundance are likely to be most pronounced in England and Wales. It may be that some species, such as Common Tern and Black Guillemot, will colonise new areas within Britain and Ireland as the climate changes, to some extent compensating for abundance declines within the current range or enhancing abundance increases; however, it is likely that such capacity for colonisation will be limited and dependent on availability of suitable habitat.
Having analysed the relationships between seabird abundance and climate/oceanography, there was the opportunity to explore the nature of these relationships across species. These relationships varied greatly between species, but both abundance and presence were typically negatively related to maximum air temperature during the breeding season. Further investigation of these relationships could help identify the mechanisms by which climate influences seabirds. This in turn could help with the identification of conservation strategies that might mitigate the impact of climate change on seabirds.
The predicted abundance changes from this study can be used in climate change vulnerability assessments for each species. More generally, the study helps warn of another growing threat to seabirds, emphasising the importance of taking conservation action where possible.
Abstract
Estimating species’ vulnerability to climate change is a key challenge in conservation. Many seabird species are particularly sensitive to negative effects of warming and are thus threatened by climate change. We projected seabird abundance in 2050 in Britain and Ireland, an internationally-important region for seabirds, under climate change scenario RCP8.5. Our projections were based on fitted relationships between abundance and both climatic (air temperature, precipitation) and oceanographic (sea surface temperature, potential energy anomaly) variables, estimated using a Bayesian hurdle model with spatial random effects. The most consistent responses to environmental variables were negative relationships between species presence or abundance and breeding season maximum terrestrial air temperature. Although data and modelling issues meant that future projections could be made for only 15 of the 25 species and with low predictive power for spatial abundance, predictive power was high for spatial presence and moderate for temporal abundance change. Projections suggest that seabirds will generally fare poorly under climate change in Britain & Ireland, with 10 species projected to decline in abundance by 2050. Variable model fit and projection uncertainty limited confidence, which was generally greater for declines than for increases. Fulmar, puffin and Arctic tern were each projected to decline by over 70% with higher confidence. For a few species, colonisation of new areas may reduce projected losses, but this is potentially limited by suitable habitat. Projected abundance change was more negative for marine specialists than for generalists. Our findings highlight the vulnerability and conservation needs of seabirds in a changing climate.
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