Humans are causing the tree of life to lose all its branches, according to a new study published Monday that warns of a sixth mass extinction.

“The extinction crisis is as grave as the climate change crisis. It is unrecognized,” said Gerardo Ceballos, professor at the National Autonomous University of Mexico and co-author of the study. Sciences (PNAS.)

“The future of humanity is at stake,” he told AFP.

The study is unique because instead of examining the loss of just one species, it examines the extinction of an entire species. The classification of living things is between genus, species and family. For example, dogs are a species belonging to the genus Canis, that is, the canidae family.

“This is a really important contribution, I think it’s the first time anyone has tried to estimate modern extinction rates at a level above the species level,” said Robert Cowie, a biologist at the University of Hawaii who was not involved in the study. AFP.

“This really exhibits the loss of all the branches of the Tree of Life,” a view of living things first developed by Charles Darwin.

Anthony Barnosky, professor emeritus at the University of California at Berkeley, agrees that the study shows that “we’re using chainsaws to get rid of large branches, not just cutting terminal branches.”

73 extinct species

Researchers relied mainly on species listed as extinct by the International Union for Conservation of Nature (IUCN). They focused on vertebrate species (excluding fish) for which additional data were available. They concluded that 73 of approximately 5,400 species (including 34,600) have become extinct in the last 500 years, most of them in the last two centuries.

The researchers then compared this to extinction rates estimated from the fossil record over a very long period.

“Based on the extinction rate over the past millions of years, we expected two species to disappear. But we lost 73,” Ceballos explained.

Researchers estimate that this should take 18,000 years, not 500 years, but such estimates remain uncertain because not all species are known and the fossil record remains incomplete.

Reason? Destruction of crop habitats or infrastructure as well as overfishing, poaching, etc. human activities such as. Ceballos argued that the loss of one species can have consequences for the entire ecosystem.

“If you take one brick, the wall won’t fall down,” he said. “You’ll get a lot more, and eventually the wall will come down.” “What worries us is that…we are losing things so fast that for us it is a sign of the collapse of civilization.”

“There’s still time” to act

All experts agree that the current extinction rate is alarming, but whether this is the beginning of the sixth mass extinction (the last one was an asteroid that wiped out the dinosaurs 66 million years ago) remains a matter of debate.

Scientists generally define mass extinction as the disappearance of 75 percent of a species in a short period of time. Using this “arbitrary” definition, Cowie said the sixth mass extinction has not yet occurred.

But “assuming species continue to disappear at the current rate (or faster), then that’s going to happen,” he warned. “We can definitely say that this is the beginning of a potential sixth mass extinction.”

Ceballos warned that the window of opportunity for people was “quickly closing”. He said the priority is to stop the destruction of natural habitats and regenerate those that have been lost.

“But there is still time to save many species,” he said. “There are 5,400 species, and if we act now we can save many of them.” Source