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Evolution Can’t Keep Up With Mammal Extinction

It will take millions of years for mammals to recover from damage caused by humans, new study finds

A polar bear in the water just outside the Inupiat village of Kaktovik, Alaska, 2017. As climate change shrinks their natural habitat, polar bears are turning Kaktovik into their very own sanctuary city.

It’s going to take mammals at least three to five million years to recover from the damage humans are doing to the planet.

JIM LO SCALZO/EPA-EFE/Shutterstock

Earlier this month, a daunting U.N. report laid out in no uncertain terms that humans need to drastically change the way we live, and fast, to avoid a major crisis — without a massive shift, more extreme weather, unlivable conditions, increased poverty and food scarcity are all in our not-too-distant future. The report also conceded that such change doesn’t seem likely. A week after the report, President Trump (who pulled the U.S. out of the Paris Agreement on climate change) reiterated that he doesn’t believe that climate change is man-made — contrary to the convictions of at least 97 percent of actively publishing climate scientists. The Trump administration enthusiastically supports the coal industry, one of the biggest culprits in carbon emissions, and has rolled back regulations, the opposite of what the U.N. report urged.

So, barring a miracle, it looks like we’re just going to have to watch as the planet loses coastlines and stable weather, and apparently we won’t even have coffee or beer to get us through it, as crops are threatened by draught and extreme heat, leading to shortages. But it won’t stop there.

Biodiversity is one of the biggest things we stand to lose to climate change. A team of researchers from Aarhus University and the University of Gothenburg have determined that, if extinction rates continue as they have for the next five decades, it’s going to take mammals at least three to five million years to recover from the damage humans are doing to the planet. The extinction of various species is part of the natural cycle of the Earth’s living organisms — some species die out, sometimes even en masse, and others evolve to replace them. But thanks to human involvement, mammals are going extinct at such a rapid rate that evolution can’t keep up.

Researchers used an extensive database of mammals — including those that have gone extinct since modern humans existed — and evolutionary simulations to determine how much time recovery would take if mammals continue to die off as they have for the next 50 years. And the three- to five-million-year estimate is just how long it would take biodiversity to get back to today’s levels. It would take five to seven million years to get back to the levels before modern humans evolved and started messing everything up.

Their estimates of recovery time were based on an extremely optimistic projection of a future where humans have stopped damaging the planet, which, clearly, doesn’t seem to be the future we’re heading toward.

The black rhino and Asian elephants are just two of the species that are expected to go extinct soon, unless there are dramatic changes in our efforts to protect them. These two are particularly significant potential extinctions, because they’re evolutionarily distinct, meaning that there aren’t other similar animals out there to serve the same functions as them if they die off. When an evolutionarily distinct species goes extinct, we lose not only that animal, but whole systems that rely on it.

“Large mammals, or megafauna, such as giant sloths and sabre-toothed tigers, which became extinct about 10,000 years ago, were highly evolutionarily distinct. Since they had few close relatives, their extinctions meant that entire branches of Earth’s evolutionary tree were chopped off,” said paleontologist Matt Davis from Aarhus University, who led the study. “There are hundreds of species of shrew, so they can weather a few extinctions. There were only four species of sabre-toothed tiger; they all went extinct.”

The one positive note in this report is that the data and methods these researchers used could also help identify the most evolutionarily distinct species that are currently at risk, so we could theoretically focus our conservation efforts on protecting them, and minimize the damage we’re doing. “It is much easier to save biodiversity now than to re-evolve it later,” Davis said.

In This Article: Climate Change, science

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