Humans have contributed to animal extinction since the Late Pleistocene, and a new study suggests there are more than 500 species to follow by the year 2100.

A team of researchers from Europe has looked at fossil records to observe the trends of mammalian extinction rates from the past 126,000 years. The study, published in the journal Science Advances on Friday, September 2, assess human impact on mammalian extinction events in the past and in their predicted future.

Woolly Mammoth - An Extinct Mammal
(Photo: Flying Puffin via Wikimedia Commons)
In the Royal BC Museum in Victoria (Canada). The display is from 1979, and the fur is musk ox hair.

An Increase in Extinction Rates of an Unprecedented Magnitude

The researchers employed Bayesian models to fossil records in order to observe the behavior of mammalian extinction rates. Through the use of posterior predictive methods, researchers tested the hypotheses of human-caused extinction events.

Through this model, researchers were able to observe that the size of the human population predicted previous extinctions with an accuracy of 96 percent. The study notes that though there are other factors for extinction events in the Pleistocene period, "the human impact in the most recent extinctions (since 1500 CE) is undeniable."

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To test their hypothesis, the researchers collected the most recent fossil reports covering 351 mammal species globally known to be extinct since the start of the Late Pleistocene. To address the incomplete samples in the fossil records they collected, they estimated extinction times through estimated preservation rates in the fossil samples available.

Generally, the study suggests that extinction rates have increased around the world compared to the start of the Late Pleistocene - by about 1,700 times. To put the current extinction rates in perspective, all 351 recorded mammal extinctions would have occurred in only 810 years, or about 1.75 million years if the extinction rates have remained steady from the start of the Late Pleistocene.

Based on the current extinction status of animals based on assessments by the International Union for Conservation of Nature (IUCN), the researchers simulated their own time frame. According to the IUCN scenario, about 558 species of mammals (confidence interval from 502 to 610) around the world will be extinct by 2100.


Losing Unique Portions of Earth's Natural History

In an article from BBC, Tobias Andermann, first author of the study from the University of Gothenburg and the Gothenburg Global Biodiversity Centre, expressed optimism. He explains that hundreds or thousands of species could be saved from extinction with targeted and efficient conservation strategies. Increased collective awareness is important regarding the escalating biodiversity crisis, adding that we must take action in working against the global emergency.

"With every lost species, we irreversibly lose a unique portion of Earth's natural history," Andermann said.

Professor Samuel Turvey, the co-author of the study from the Institute of Zoology at the Zoological Society of London, noted the importance of looking at previous records. "Reconstructing our past impacts on biodiversity is essential to understand why some species and ecosystems have been particularly vulnerable to human activities - which can hopefully allow us to develop more effective conservation actions to combat extinction," Turvey said.

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The new study is in line with a 2019 report released by the Intergovernmental Panel for Biodiversity and Ecosystem Services or IPBES, which estimates that close to a million species of flora and fauna face the risks of extinction.

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