PORTLAND, Maine – Global warming is wreaking havoc on seabirds who are suffering from declining populations due to starvation, inability to reproduce, heat waves and extreme weather conditions.
Climate-related losses have affected albatrosses off the Hawaiian Islands, northern gannets near the British Isles and puffins off the coast of Maine. Some birds are less able to build nests and raise young when sea level rises, while others are unable to find fish to eat when the ocean warms, researchers have found.
Common Murres and Cassin’s Stariques that live off the west coast have also died in large numbers from scientific conditions directly related to global warming.
With less food, rising seas encroaching on islands where birds roost, and increasingly frequent hurricanes clearing nests, many seabirds have produced fewer chicks, the researchers say.
And the tern species that live off New England have died in the increase in rains and hailstorms that scientists have linked to climate change. Some species, including endangered roseate terns, also can’t fly because more frequent severe weather kills their young, said Linda Welch, a biologist with the US Fish and Wildlife Service.
The warming world is increasingly inhospitable to many seabirds, Welch said. “Over the past two years, they have experienced widespread nesting failure,” she said. “I really think there are big ramifications for what we are seeing.”
It is difficult to accurately determine the loss of wide range seabird population and how much is due to climate change. But an estimate from researchers at the University of British Columbia said seabird populations have fallen 70% since the mid-20th century.
Breeding success has also declined over the past half century for piscivorous seabirds, especially those that live north of the equator, according to a study published earlier this year in the journal Science.
Researchers at the University of Washington and other institutions who have studied dozens of species of seabirds around the world have found that some were successful at reproducing at just 10% of historical levels. They also found that in the southern hemisphere, difficulty finding fish prevented species such as the Magellanic penguin from successfully feeding chicks.
Worldwide, seabirds are under threat in large part due to warming ocean temperatures, scientists say. Over the past five decades, more than 90% of the additional heat on the planet due to global warming has been absorbed by the ocean, according to US government scientists.
Warming seas, coupled with massive mortalities that kill thousands of birds by starvation, make it harder for some species to maintain stable populations, said P. Dee Boersma, professor of biology at the University of Washington and author of the Science study.
Seabirds, such as penguins which have declined by nearly three-quarters in South Africa since 1991, are a harbinger of what will happen to wildlife with global warming, Boersma said.
“These ecosystem sentinels are important because they are not only nice for us to be able to see them, but they are important as a signal that we have gone too far,” she said.
One of the most serious threats to seabirds is the reduction of plankton and small fish in the cold northern waters. The loss of forage fish and plankton has resulted in the massive deaths of birds such as the Cassin’s Stariques which have stranded in the tens of thousands on the Pacific coast in recent years.
One of the most visible examples of the impact of global warming on seabirds has been the deaths of tens of thousands of Common Murres along the west coast in the mid-2010s. washed up on a single beach near the Chugach National Forest in Alaska.
Scientists later determined that the warming waters deprived the birds of the abundant sardines and anchovies they gorged on, and the birds starved to death. The deaths occurred amid a sea heat wave known as the “stain”.
Thousands of miles away in the North Sea, a similar problem has forced northern gannets to forage for food further away, leaving the chicks unattended and vulnerable to predators, researchers at the University of Leeds.
Another concern is sea level rise. Albatross colonies in the Central Pacific and Hawaiian Islands depend on low-lying areas that experience larger flooding and storms, said Don Lyons, director of conservation science at the Seabird Institute of The Audubon Society.
“People are really concerned about a few decades,” Lyons said.
Maine’s iconic seabird, the Atlantic puffin, suffered one of its worst breeding years in decades this summer due to a decline in the availability of the small fish it eats.
The Gulf of Maine, where puffins nest on tiny islands, is warming faster than most of the world’s oceans, which has reduced forage fish populations, scientists say. Poor breeding, which has persisted for several years in puffins, is a “stern warning” about the future of seabirds, Lyons said.
“Seabirds are one of the most visible indicators of the health of our oceans,” said Shaye Wolf, director of climate science at the Center for Biological Diversity. “These escalating seabird mortalities are big red flags that rising ocean temperatures are wreaking havoc.”
Follow Patrick Whittle on Twitter: @pxwhittle