It Could Take Mammals 7 Million Years to Recover From Humanity Wiping Them Out

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Elephants’ brethren—including mastodons and mammoths—once ranged across the Americas, Eurasia, and Africa. But natural climatic changes helped shrink their range and human hunters ensured their demise, leaving just elephants alive and confined to parts of Africa and Asia today.

The fate of elephants is hardly isolated in the mammal world: Humans have proven to be ruthless killing and displacement machines by hunting animals to death and wiping out habitat. Add in climate change and chemicals seeping into the environment, and it’s a recipe for altering the entire fabric of life on Earth. New findings published on Monday show that the alterations we’re making could outlast humanity itself.

The research in the Proceedings of the National Academy of Sciences focuses on what’s been going on with mammals and humans since the Late Pleistocene, which began roughly 130,000 years ago. During that time—but particularly during the last 12,000 years of the Holocene—we’ve seen humanity flourish at a heavy toll on the wild world. Clearing land for farms and cities meant less habitat to go around for animals, and hunting meant less animals and disruptions to the food web. The new study quantifies those changes as well as how long it could take life to recover by assessing something called phylogenic diversity. It’s a metric that includes how long species have been around and touches on the functional niche they fill.


The findings are sobering. The mammals we’ve relegated to history books over the past 130,000 years represent a combined 2.5 billion years of evolutionary history. About 20 percent of the biodiversity losses have occurred in just the last 1,500 years alone, and the trend will accelerate if we continue rapaciously consuming land and speeding climate change along with rising carbon emissions.

“This study tells us key traits about the potential future of mammals given the evolutionary history that they’ve just recently lost,” Nick Pyenson, a paleobiologist at the Smithsonian Institution, told Earther. “It’s certainly a stark outlook, in the big picture.”

The researchers then modeled what would happen over the next 100 years if we threw all our efforts into conservation immediately. Starting now would obviously help us preserve the mammals we have left, but it would still take a whopping 500,000 years restore the lost mammalian diversity because evolution is a slow, incremental process. If we continue with our status quo efforts for the next 100 years before going all in on conservation, recovery time balloons to 5-7 million years.

“I have to admit this was a depressing paper to write, Matt Davis, a postdoc at Aarhaus University in Denmark who led the research, told Earther. “I’m worried we wont start [fixing things] now.”


Davis also joins a growing chorus of scientists who say the sixth mass extinction is unlike ones that have occurred in the past. Earth’s previous five mass extinctions were indiscriminate in comparison to our current human-driven one, which disproportionately affects large mammals. That means not only are we losing charismatic megafauna, we’re pushing into uncharted territory where small mammals rule the Earth.

“Instead seeing elephants, you’ll see rats,” Davis quipped. Sounds like a fun safari.


But beyond losing pretty mammals, we also stand to lose a lot more as the complex ecological web unravels. Seeds won’t get dispersed in poop, which affects pollinators, which affects animals down the food chain. Fewer pollinators could affect crops, if you prefer a more human-centric view. Manuela Gonzalez-Suarez, an ecologist at the University of Reading, told Earther she was loathe to boil the impacts down to just ecosystem services since it’s about more than dollars and cents. Instead, she put it in more stark terms.

“These are the things that make the Earth work,” she said. “That’s what we need to worry about.”