Human impact can explain ninety-six percent of all mammal species extinctions of the last hundred thousand years, according to a new study led by Professor Daniele Silvestro at the University of Fribourg and Tobias Andermann of the University of Gothenburg.

The extinction rate of mammals is currently more than a thousand times higher than the natural rate, and this increase is caused almost exclusively by humans. The new study suggests that humankind has had a much greater influence on biodiversity than climate change, even when compared to temperature variations as great as those of the last Ice Age. The study was published this week in Science Advances, in collaboration with Swedish, Swiss and English researchers.

Fossils of 351 species of extinct mammals
The researchers compiled and analysed fossil data for 351 species of extinct mammals, including the iconic species such as mammoths, sabre-toothed tigers and giant ground sloths. These extinctions did not happen continuously and at constant pace. Instead, bursts of extinctions are detected across different continents at times when humans first reached them. More recently, the magnitude of human-driven extinctions has picked up pace again, this time on a global scale.

Specialists are aware of the coincidence between the arrival of humans and the disappearance of mammals, for example in the case of large animals on the American continent. But while most previous studies focus on one region and certain species, this one considers all continents and all extinct mammals, including many rodents, for example, whose extinction is less spectacular. An advanced modelling procedure allowed the team to disentangle the effects of humans and climate and test their respective influences. Some scholars believe that strong climatic changes were the main driving force behind most pre-historic mammal extinctions, for example in the disappearance of iconic species like the mammoths or woolly rhinoceroses. The study published this week advances strong arguments in favour of the main influence being that of human settlement. "Mammoths, for example, survived several ice ages before the last one and there is no climatic reason why they should not be alive in Siberia today," adds Daniele Silvestro.

An ongoing wave of extinctions
Using models and computer simulations, the researchers were able to demonstrate the close link between the density of human population and the extinction rate. They predict that these rates will continue to increase rapidly - possibly reaching up to 30,000 times the natural level by the year 2100 - should the current trends in human behaviour and biodiversity loss continue.

These bleak prospects are not inevitable. "We can save hundreds of species from extinction with more targeted and efficient conservation strategies," concludes the first author of the article, Tobias Andermann at the University of Gothenburg. “But in order to achieve this, we need to increase our collective awareness about the looming escalation of the biodiversity crisis and take action to combat this global emergency. Time is pressing. With every lost species, we irreversibly lose a unique portion of Earth’s natural history. »

• Link to original manuscript: "The past and future human impact on mammalian diversity", published in Science Advances.
• Copyright: Tobias Andermann