Scientists warn that entire branches of the “tree of life” are becoming extinct

The Humans are causing the loss of entire branches of the “tree of Life”according to a new scientific study published Monday that warns of the threat of a sixth mass extinction.

“The extinction crisis is as serious as that of climate change”, warned Gerardo Ceballos, professor at the National Autonomous University of Mexico (UNAM) and co-author of the research published in the journal Proceedings of the National Academy of Sciences (PNAS).

“What is at stake is the future of humanity,” declared the expert to AFP.

The study is exceptional in that, rather than simply examining the loss of one species, it examines the extinction of entire genera.

In the classification of living beings, the genus is situated between the range of species and family. For example, dogs are a species belonging to the genus canis, which in turn belongs to the canid family.

“It’s a really significant contribution, I think the first time anyone has tried to assess modern extinction rates at a higher than species level.”Robert Cowie, a biologist at the University of Hawaii, who was not involved in the study, told AFP.

“As such, it really demonstrates the loss of entire branches of the ‘tree of life,’” a famous representation of living beings first developed by Charles Darwin.

Research shows that ““Not only are we trimming terminal branches, but we are taking a chainsaw to get rid of big arms.”agreed Anthony Barnosky, professor emeritus at the University of California, Berkeley.

73 extinct genera

The researchers relied mainly on species classified as extinct by the International Union for Conservation of Nature (IUCN). They focused on those vertebrates (excluding fish), for which more data is available.

Of some 5,400 genera (comprising 34,600 species), they concluded that 73 had become extinct in the last 500 years, most in the last two centuries. The scientists then compared this figure with the extinction rate estimated from existing very long-term fossil records.

“Based on the extinction rate in the previous million years, we would have expected to lose two genera. But we lost 73″Ceballos explained.

The study estimates that 18,000 years should have passed, not 500, although these estimates remain uncertain as not all species are known and the fossil record is incomplete.

The cause? Human activities, such as the destruction of habitats for crops or infrastructure, as well as overfishing, hunting, etc. The loss of a genus can have consequences for an entire ecosystem, Ceballos warned.

“If you remove a brick, the wall doesn’t collapse,” he said. “If you remove too many more, the wall will eventually collapse.”

“Our concern is that… we are losing things so quickly, that for us it is a sign of the collapse of civilization”said.

In time to act

All experts agreed that the current rate of extinction is alarming, but it continues to generate debate whether this situation represents the beginning of a sixth mass extinction (the last one corresponds to the one generated by the asteroid that wiped out the dinosaurs 66 million years ago). .

Broadly speaking, scientists define a mass extinction as the loss of 75% of the species in a short period of time. Using that definition “arbitrary”Cowie said, a new one has not yet been produced.

But if we suppose that “species will continue to become extinct at the current rate (or faster), then it will happen,” he warned. “We can safely say that this is the beginning of a potential sixth mass extinction.”

Ceballos warned that the window of opportunity for humans to act “it is closing quickly.” The priority is to stop the destruction of natural habitats and restore those that have been lost, he said.

“But we still have time to save many genres”he claimed. “There are 5,400 genres, we can save many of them if we act now”.

Source: AFP