Polar Bears International

Do recent studies on the polar bear's evolution alter the risks polar bears face as the world warms?

Answered by Dr. Steven C. Amstrup, chief scientist at Polar Bears International and Polar Bear Project leader at the U.S. Geological Survey for thirty years.

Q. A research paper published in 2012 suggested that the polar bear species may be up to five million years old. In 2014, two newer papers suggest that polar bears may have diverged as a species only 300,000 to 500,000 years ago. Do these varying results alter the risks polar bears face as the world warms?

A. A 2012 DNA study of polar bears and brown bears pushed back the polar bear's origin to about five million years ago. Most recently, genetics researchers have returned this split to less than 600,000 years.

All these recent studies are interesting in terms of understanding how polar bears got to where they are today. But none really alter the risks polar bears face if we allow the climate to continue to warm.

Whether polar bears are 150,000 years old or five million years old, unless we take action to curb greenhouse gas emissions, they face a future where the climate will continue to warm. And this warming will eventually exceed anything they have previously experienced.

You would have to go back to the Pliocene (about three million years ago) to find temperatures as warm as they are likely to be in 50 years. But it's important to remember that surviving a natural climate cycle is a very different thing from surviving a continuing warming that will exceed Pliocene levels in 100 years and keep going unless we greatly reduce greenhouse gas emissions.

It's also important to remember that just because polar bears began to branch off from grizzly bears as early as five million years ago, there is no evidence that the early ancestors were polar bears as we know them today.

Polar bears now are very highly specialized to a sea ice environment. And if some of their genes continue through breeding with grizzlies in a much warmer future world, that doesn't mean that the creature we now know as a polar bear will continue. In other words, the polar bear would no longer be a polar bear.

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