Massive loss of seabirds in Alaska occurres after heat wave in Pacific Ocean

By Alimat Aliyeva

The large-scale warming of surface waters in the Northeastern Pacific Ocean in 2014-2016, known as the "warm blob," caused catastrophic consequences for marine ecosystems. One of the most affected groups was seabirds, particularly thin-billed kittiwakes, predators that depend on the availability of small fish, Azernews reports.

A study conducted by the U.S. Fish and Wildlife Service and published in the journal Science showed that about 4 million kittiwakes died during the heatwave, which is half of their population in Alaska. An analysis of data from 13 colonies, covering the period from 2008 to 2022, revealed a sharp decline in the number of birds.

In the Gulf of Alaska, the number of birds decreased by 50 percent. In the eastern part of the Bering Sea, losses amounted to 75 percent.

Before the "warm blob," about 8 million kittiwakes lived in Alaska, a quarter of the world population. Today, their number has fallen to 4 million, and no recovery has been recorded over the past seven years.

Scientists have found that the main factor in the death of the birds was not heat stress, but drastic changes in the food chain. The warming of the ocean led to a decrease in ecosystem productivity, which caused a shortage of fish, a key food source for kittiwakes. Analysis of the birds' remains showed that most of them died of starvation.

"These results clearly demonstrate the long-term effects of the marine heatwave on marine predators," said Julia Parrish, a professor at the University of Washington and co-author of the study.

Although the "blob" became one of the strongest marine heatwaves, such phenomena are becoming more frequent due to climate change. A 2023 study, in which many of the authors of this work participated, showed that an increase in ocean surface water temperature of just 1°C over six months can cause mass deaths of seabirds.

"The frequency and intensity of such events increase with ocean warming. We may be at a stage where the ecosystem is being rebuilt, and a return to the previous state may not be possible," said Parrish.

The recovery of seabird populations after a heatwave usually takes about three years, but the kittiwakes in Alaska show no signs of population growth even after seven years. This raises concerns among scientists and raises questions about the future sustainability of marine ecosystems.

Participants in the University of Washington's Citizen Science program made a significant contribution to data collection. Volunteers living on the coasts helped record cases of mass bird deaths, which became an important source of information for analysis.

The authors of the study emphasize that the preservation of marine ecosystems requires not only monitoring but also active measures to reduce the effects of climate change to prevent further disasters.