DAILY SCIENCE

In new bird extinction estimates, a dark picture—and a glimmer of hope
To prevent a wave of bird extinctions, nature-loving people need to protect common species, too.
January 22, 2020

In a time of unhappy environmental news, it can be hard to stomach yet another tale of imminent loss—but there are important lessons to be learned from a new assessment of Earth’s birds and their possible fates.

Researchers led by biologists Melanie Monroe of Simon Fraser University and BirdLife International’s Stuart Butchart wanted to get a better understanding of modern avian extinction rates, which are usually calculated by comparing the number of bird species who have vanished in the last few centuries to that number in deep historical time.

By that light, 187 bird species have gone extinct in the last 500 years, a span of time during which—in the absence of cataclysm—just three or four birds would normally disappear. It’s a dramatic acceleration of loss, in keeping with an understanding of the present human-dominated era as one of global mass extinction, yet it may actually understate the pace of decline.

Writing in the journal Biology Letters, Monroe and colleagues describe a different way of calculating extinction rates. Rather than looking to historical records, they draw upon extinction risk categories—from “least concern” through “critically endangered”—assigned by the International Union for the Conservation of Nature to more than 10,000 bird species across the last 28 years.

Most are closer to extinction now than they were 28 years ago. They might not be endangered, and many are still not even considered threatened, but their trajectory is pointing downwards. When the researchers modeled those trajectories into the future, they arrived at extinction rates roughly six times higher than current mass-extinction estimates.

Another, especially poignant way understanding those numbers is offered by calculate the average expected lifespan of a species. Across evolutionary history, vertebrate species generally existed for three million years before fading. At Monroe and colleagues’ newly-derived rates, a contemporary species can be expected to survive slightly less than 5,000 more years.

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Yet there’s a positive side to this. The researchers also calculated extinction rates in the absence of conservation efforts that have resulted in species becoming less-endangered in recent decades. They found that conservationists have slowed those rates by 40 percent. That’s no small accomplishment. Conservation works, and the situation would be far more dire without it.

In the long run, though, the researchers suggest that present approaches, which focus on preventing imminent extinction by targeting already-threatened or endangered species, will not suffice. Much more attention should be paid to “keeping common species common,” they write, and to helping those now considered threatened, but not urgently so. Only by changing those trajectories can people  “help dampen an ever-building wave.”

The researchers also write that their calculations are “an illustration of the process currently taking place and not a prediction of what will happen in the future.” Extinctions are not written in stone. Nature-loving people can still prevent them. We just need to expand our field of view.

Source: Monroe et al. “The dynamics underlying avian extinction trajectories forecast a wave of extinctions.” Biology Letters, 2019.

Image: Envato

 

About the author: Brandon Keim is a freelance journalist specializing in animals, nature and science. He is now writing Meet the Neighbors, a book about what animal personhood means for our relationships to animals and to nature. Connect with him on Twitter, Instagram and Facebook.

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