Reaching Paris climate objectives could help stabilize seabird distribution

Reaching Paris Agreement objectives will likely bring stability to the winter distributions of seabird species in the North Atlantic Ocean.

But a recent study shows if carbon emissions aren’t reduced, and the average global temperature warms more than 2 degrees Celsius, the ways seabirds are distributed could be impacted during the winter months.

As a result, mitigation to limit greenhouse gas emissions and slow down global warming can directly impact migrating seabirds’ behavior and help stabilize their distribution. “For the mitigation scenario, fortunately there are very few changes in the seabird distribution,” said Manon Clairbaux, a postdoctoral research at the Center for Evolutionary and Functional Ecology and the University of Montpellier in France and the lead author of the study published in Global Change Biology.

Researchers equipped seabirds like this black-legged kittiwake with tracking devices. Credit: Anker-Nilssen Tycho

Seabirds like little auks (Alle alle), Atlantic puffins (Fratercula arctica), common murres (Uria aalge), thick-billed murres (Uria lomvia) and black-legged kittiwakes (Rissa tridactyla) represent more than 75% of the seabirds breeding in the North Atlantic. These species depend on zooplankton or the small fish that feed on the small marine creatures. The zooplankton thrive only in certain water temperatures that will likely shift if global average temperature increases too much as a result of unmitigated burning of fossil fuels.

Clairbaux and her co-authors set out to predict the ways that seabird ranges might shift in the winter months when the migrants are in the southern part of their annual ranges. The team tapped into tracking data for about 1,500 individuals from the five species, collected from nine countries by more than 20 research institutions They linked bird distribution with the availability of prey like zooplankton and fish and looked at how much energy the birds required in their winter areas to understand why they choose some places over others.

Little auks in eastern Greenland. Credit: Manon Clairbaux

“The [seabirds] go places to maximize energy intake,” said Clairbaux, who conducted the study while she was working on her PhD at the University of Montpellier, supervised by David Grémillet.

They matched seabird locations with their prey availability and energy requirement for each wintering month. Both prey availability and the energy seabirds spend to find it depend on temperature. The team projected those variables into the future according different climatic scenarios, then established the likely future winter distribution of seabirds.

“We could project this mathematical link to the future,” Clairbaux said.

Common murres might experience an increase in their winter range size, though they will shift further north, if climate goals aren’t met. Credit: Jeremy Tornos

They found that the winter distribution of the five species wouldn’t change much if the global average temperature were to increase by less than 2 degrees Celsius above pre-industrial levels.

If the global temperature average increased more than that, though, they found that the five seabird species responded differently. The winter areas used by little auks, which represent the most populous seabirds in the North Atlantic, and black-legged kittiwakes, for examples, would shrink as temperature increases due to decreased zooplankton availability in the southern part of their range.

They found the opposite for the common and thick-billed murres, which may actually benefit from warmer temperatures.

“For those two species, the energy requirement at very high latitudes is predicted to decrease, and the fish they eat are also predicted to shift northward,” Clairbaux said.

A thick-billed murre. Credit: Jeremy Tornos

Their models showed that Atlantic puffins wouldn’t experience much of a change. Their overall winter distribution might shift slightly northward, but wouldn’t change much in size, Clairbaux said.

Even while some species like murres might see larger winter distributions, the changes might not be beneficial overall to the North Atlantic Ocean’s ecosystem.

“We will probably observe that many of the species will shift to the Arctic Ocean,” Clairbaux said.

But the information they gathered on future ranges, and further studies to predict the ways that seabird distribution might change, could help wildlife managers plan marine conservation areas that will better reflect future ranges.

Atlantic puffins may not experience much change. Credit: Bernard Alice