A new study shows that seasonal increases in ocean temperatures can have dramatic consequences for many important seabird populations in the region.
A warmer North Atlantic Ocean increases the pressure on seabird populations, of which many are already in decline. A large-scale study of 26 populations of five species reveals that increasing temperatures – especially outside of the breeding season – affects survival, breeding success and future population growth.
Large-scale study
Climate change is causing ocean warming, acidification and loss of sea ice. This, in turn, is leading to shifting biogeographic distribution and in some cases species extinction. The result is disrupted marine food webs, from the primary producers to top predators. However, the rates of ocean warming vary between regions because of global ocean circulation patterns. To identify the wide consequences of ocean warming on migrating species such as seabirds, it is therefore essential to compare multiple populations with a range of breeding and nonbreeding habitats.
Combination of monitoring data
Three types of data were integrated in this study: (1) long-term demographic monitoring (reproduction and adult survival) data from the 26 populations, (2) year-round tracking data – that is, the seasonal distribution of birds across the oceans – and (3) observations of sea surface temperatures (SST) in the areas used by the birds. By combining year-round distribution with temperature data, the researchers could analyse how ocean warming at different times of the year correlated with negative effects on survival and population sizes.
One effect of ocean warming is that adult black-legged kittiwakes struggle to find enough food for their chicks. Photo: Signe Christensen-Dalsgaard/NINA.
Sensitivity to warming in autumn and winter
The results revealed that negative effects of ocean warming were largely related to warm periods in the autumn or winter, particularly in the Barents and East Greenland Seas. Effects of warming in the breeding season were, in general, less profound. Populations with dual responses to warming in both the breeding and nonbreeding seasons had the lowest projected population growth rates.
– Seabirds live in a fine-tuned interaction with the marine environment. When ocean temperature increases faster than the species are able to adapt, their reproduction and survival capacity are directly affected, says researcher and first author behind the study, Kate Layton-Matthews.
Management needs to focus on multiple factors
The study underlines the need for management strategies that take migration routes, seasonal habitat use and regional climate change into account – factors that may decide the fate of the North Atlantic seabirds.
– If we are to secure these populations in the future, we must improve our year-round monitoring and consider how climate changes affect the different parts of birds’ life cycle, Layton-Matthews states.
Read article: Demographic responses of North Atlantic seabirds to seasonal ocean warming
Contact: Kate Layton-Matthews