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Study: Climate change threatens half of bird species in North America

Common Loon (Gavia immer), Logan Lake, Longford Township, Ontario.
Common Loon (Gavia immer), Logan Lake, Longford Township, Ontario.

As global warming progresses, many animals, birds, fish, and plants will have to relocate in order to maintain their current climate conditions. Some species will be able to adapt just fine. Others will struggle. Still others might just die off.

Case in point: The National Audubon Society has a big new report out today looking at how 588 different bird species across North America will see their habitats shift because of global warming.

Of those, the report finds, 314 species are likely to lose more than half their current climactic range by 2080. That's a dramatic change, and it's not clear whether all of those birds will be able to survive the shift.

Here's what this shift in habitat looks like in animated map form for the Common Loon (Gavia immer):

common loon range

(National Audubon Society)

For 588 different species, the Audubon scientists used data from hundreds of thousands of observations to outline the birds' current climatic ranges — that is, the temperatures, seasonality, and precipitation that the birds need to survive. That includes where the birds migrate for the winter, where they go for the summer breeding season, etc.

The researchers then used global-warming projections to get an estimate for where those birds were likely to move as the world warms — assuming that the birds wanted to maintain their current climatic conditions.

So take the Common Loon, shown in the map above. It currently breeds throughout Canada and parts of the northern United States during the summer — preferring large lake areas in order to catch fish — and then makes its way down both US coasts during the winter. As the world gets hotter, the bird is likely to lose roughly 56 percent of its preferred breeding range. By 2080, once-frequent loon sightings in Minnesota may be a thing of the past.

And that's just one species. "Suitable breeding grounds for the Baird's Sparrow could disappear entirely," writes Michelle Nijhuis in Audubon. "The Piping Plover, an icon of the Atlantic Flyway, may vanish from many eastern shores."

Another striking finding? As many as nine states may see their state birds vanish from within their borders in the coming century, thanks to this habitat shift.

So how many birds will survive this shift?

piping pover

Piping plover, one of the bird species whose range will shrink in the coming decades. (US Fish and Wildlife Service)

It will likely vary from species to species — some will no doubt survive, others may struggle.

But on average, animals typically face an increased risk of extinction as their geographic range shrinks — and they run out of suitable habitats to reproduce and find food. This relationship has held pretty consistently throughout Earth's history. If, say, a bird species thrives on grasslands and is forced to move north where there are fewer grasslands, the prospects for survival go down.

Now, the caveats: This Audubon study is only a first pass at the question. It doesn't take into account, for instance, what sorts of predators the birds may face as their ranges shift, or what sort of new competition they'll face for food, or the effects of sea-level rise. It also, crucially, doesn't look at the effects of climate change in Central and South America — where many birds spend the winter.

But it does suggest that some birds are likely to face dramatic changes. In modern times, only nine bird species have ever gone extinct in North America. That number could well go up — possibly significantly — by century's end.

Further reading

Here's an overview of the Audubon report. You can check out a variety of interactive maps for various bird species here — from bald eagles to spotted owls.

Here's an op-ed in the Washington Post in which two Audubon officials talk about whether or not birds might be able to adapt to this shift. (Among other things, they suggest that conservation efforts now need to take into account the fact that bird ranges are going to shift dramatically over the next 80 years.)

Jonathan Silver wrote a good piece for Reuters last year on how a variety of species — not just birds — are already adapting to shifting climates as the world warms. For instance: "British researchers recently analyzed more than 2,000 animal and plant species in Britain and found that many had already made significant adaptations to a changing environment."

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