Two-thirds of North America’s bird species are at heightened risk of extinction if climate warming continues at the current pace, according to a new report. The study adds to a dire body of research on birds, one of nature’s most important sentinels.

Two groups of birds in Canada, those that live in the Arctic and those that live in the boreal forest, could be almost entirely wiped out if the global climate warms by 3 degrees Celsius, the report’s authors found. If our efforts to keep warming no greater than 1.5 degrees are successful, however, three-quarters of the continent’s at-risk birds would see their outlook improve.

The analysis, released Thursday, was conducted by researchers in the science division of the National Audubon Society, a non-profit conservation organization. It drew on 140 million bird observations from more than 70 different data sources. The researchers used that data to analyze how 604 bird species in Canada, the U.S. and Mexico would fare under climate warming of 1.5 degrees, 2 degrees, and 3 degrees.

“The idea of the report was to look into three possible futures, and to see what those possible futures would look like for the birds that we care about, that we love, knowing that those birds rely on the same air and water that we humans do,” says Jeff Wells, vice president of boreal conservation for the Audubon Society.

“There is a future out there that we can choose that wouldn’t be as dire for birds.”

Every species — birds, bees, trees, all wildlife — has a geographic “range,” an area in which that species has adapted to the local weather patterns, food sources, breeding conditions, and even factors as subtle as timing chick hatching to a brief glut of particularly nutritious insects. Some species have very small ranges: they exist along a very narrow band of mountaintop, for example. Other species have enormous ranges, covering much of the continent.

The study’s authors looked at how climate change would affect the suitability of birds’ ranges. Essentially, the scientists asked how hostile each bird’s homeland would become as the globe heats up, and whether newly comfortable areas would open up to those birds or not.

Birds were given a vulnerability score based on how much range they lost versus gained under each of the three climate change projections. The birds that were rated as highly vulnerable were those projected to lose a lot of their ranges, but had limited capacity to expand into new territory. These birds are at a heightened at risk of becoming extinct, since they will have lost so much of the environment they require to survive.

“They’ve done a very careful job of using existing scientific tools that are all very sensible and solid to ask questions about whether probably the most beloved group of species on Earth is facing existential trouble because of climate change,” says Jeremy Kerr, University Research Chair in Macroecology and Conservation at the University of Ottawa. Kerr, who studies the effects of climate change on biodiversity, was not involved with the research.

“And the answer, quite reliably, is yes.”

Out of the 604 bird species, 389 were scored moderately or highly vulnerable if the climate were to warm by 3 degrees: they were at a greater risk of becoming extinct. Canada’s birds as a whole face a similar fate, with 66 per cent at risk under this scenario.

But some groups fared worse than others. All 16 Arctic species were at heightened risk of extinction, and 47 out of 48 boreal forest birds.

“The extent of climate change is going to be exaggerated the further north you go, so this is of particular interest to Canadians,” says Bridget Stutchbury, a bird biologist and distinguished research professor at York University.

Stutchbury, who was also not involved in the new report, added that the boreal forest is one of the largest intact forests left in the world. Aside from being important habitat for wildlife, the boreal forest is also a massive and globally important carbon reservoir, trapping carbon that if released into the atmosphere could accelerate climate change.

“We’re using the birds as bio-indicators” — a group of species whose health signals the health of the overall ecosystem — “but obviously the forest and all the other animals in the forest are at risk too,” says Stutchbury.

Last month, a major study in the journal Science found that nearly 3 billion birds have disappeared from North America since 1970, with even common species like sparrows and blackbirds suffering massive declines.

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Importantly, the Audubon Society report found that limiting warming to 1.5 degrees would improve the vulnerability score for 76 per cent of birds at risk under the worst warming scenario in at least one season. Some 146 bird species would cease to be vulnerable at all.

The global average temperature has already increased by approximately 1.1 degrees since before the Industrial era. The Intergovernmental Panel on Climate Change recommends that nations set targets to curtail greenhouse gas emissions in order to keep warming below 2 degrees, and preferably below 1.5 degrees, which would prevent some of the worst effects of the climate crisis.

“What it shows us, what all of that work shows us, is that if we make an effort, we can turn this around,” says Kerr. “It’s very simple.”

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