Understanding climate change impacts on top predators is fundamental to marine biodiversity conservation, due to their increasingly threatened populations and their importance in marine ecosystems. We conducted a systematic review of the effects of climate change (prolonged, directional change) and climate variability on seabirds and marine mammals. We extracted data from 484 studies (4808 published studies were reviewed), comprising 2215 observations on demography, phenology, distribution, diet, behaviour, body condition and physiology. The likelihood of concluding that climate change had an impact increased with study duration. However, the temporal thresholds for the effects of climate change to be discernible varied from 10 to 29 years depending on the species, the biological response and the oceanic study region. Species with narrow thermal ranges and relatively long generation times were more often reported to be affected by climate change. This provides an important framework for future assessments, with guidance on response- and region-specific temporal dimensions that need to be considered when reporting effects of climate change. Lastly, we found that tropical regions and non-breeding life stages were poorly covered in the literature, a concern that should be addressed to enable a better understanding of the vulnerability of marine predators to climate change.

To summarize, an article had to meet the following criteria for inclusion: (i) include a clear statement that the study objectives were to investigate the potential effects of climate, (ii) report on original data analyses (i.e. reviews were not included), (iii) include analyses on quantitative relationships between a climate variable and a response variable (usually conducted by correlation), and (iv) provide explicit comparisons of changes in response variables in relation to climate through time. In the case of studies with duplicate datasets and updated analyses, we selected only one study with the longest time series, typically the most recent publication. An observation was defined as a biological response variable (demographic parameter, phenology, distribution, behaviour, diet, condition or physiological variable) and a climatic variable (e.g. Sea Surface Temperature (SST) but also including global indices such as Southern Annular Mode or Pacific Decadal Oscillation (PDO), see detailed protocol in Supporting Information sections 4 & 5).

See Readme.txt in the data.