AFP
According to a scientific study published on Monday (18), humans are causing the loss of entire branches of the “tree of life”. Research warns of the danger of a sixth mass extinction.
“The extinction crisis is as serious as that of climate change,” emphasized Gerardo Ceballos, professor at Unam (National Autonomous University of Mexico) and coauthor of the study published in the journal Proceedings of the National Academy of Sciences (PNAS). ).
“What is at stake is the future of humanity,” he said.
The study analyzes not just the loss of a species, but the extinction of entire genera. In the systematics of living things, the genus is located between the species spectrum and the family. Dogs, for example, are a species of the genus Canis, which in turn belongs to the family Canidae.
“This is a really significant contribution. “I think it’s the first time that anyone has tried to assess modern extinction rates at a level higher than that of species,” said Robert Cowie, a biologist at the University of Hawaii (USA), who was not involved in the Study.
Therefore, “it actually shows the loss of entire branches of the ‘Tree of Life,'” a famous depiction of living things originally developed by Charles Darwin.
For Anthony Barnosky, professor emeritus at the University of California, Berkeley, the analysis shows that “not only do we cut off terminal branches, but we also use a chainsaw to get rid of large branches.”
73 extinct genera
The researchers focused primarily on species that are considered extinct by the International Union for Conservation of Nature (IUCN). They focused on vertebrates (excluding fish), for which more data are available.
They concluded that of the nearly 5,400 genera (comprising 34,600 species), 73 became extinct in the last 500 years, most of them in the last 200 years. Scientists then compared this number to the extinction rate estimated from existing fossil records.
“Based on the extinction rate over the last million years, we assumed we would lose two genera. But we lost 73,” explained Ceballos.
The study suggests that these losses should have occurred over a period of 18,000 years, rather than 500 years, although the estimates remain uncertain because not all species are known and the fossil record is incomplete.
The loss of these genera is associated with human activities such as habitat destruction for agriculture or infrastructure construction, as well as predatory fishing and hunting.
This endangers the entire ecosystem, warns Ceballos. “Our concern is that we are losing things so quickly that for us this is a sign of the collapse of civilization,” he said.
time to act
All experts interviewed as part of the report agreed that the current extinction rate is alarming, but continue to debate whether this situation represents the beginning of a sixth mass extinction the latest corresponding to the one caused by the asteroid that killed the 66 million dinosaurs extinct years before.
Broadly speaking, scientists define a mass extinction as the loss of 75% of species in a short period of time. Using this “arbitrary” definition, Cowie said a new one has not yet been created.
However, if we assume that “the extinction rate continues at the current rate, then this is what will happen,” he warned, praising that this is “the beginning of a possible sixth mass extinction.”
But there is still time for him to save many genres. To achieve this, it is necessary to stop the destruction of natural habitats and restore lost habitats, he stressed.