Human-caused mass extinction wipes out species

A human-caused mass extinction is wiping out not just species but “entire branches of the tree of life,” warn the authors of a Stanford University study published today.

The analysis, carried out jointly with the National Autonomous University of Mexico and published in the scientific journal Proceedings of the National Academy of Sciences, shows that humans are causing the extinction of not only species, but also genera – the highest category into which taxonomists classify living things. . .

Scientists point to three recent victims of what many consider the sixth extinction event, as human actions are wiping out vertebrate species hundreds of times faster than they would have otherwise.

They talk about the passenger pigeon, a species that went extinct at the beginning of the last century and was endemic to North America, they talk about the Tasmanian wolf, a marsupial from Australia that also went extinct in the last century, and they talk about the Baiji, the Yangtze River dolphin. in China, a species of freshwater dolphin, also extinct. Each of these species was also the last representative of its genus.

Until now, public and scientific interest has focused on species extinction. But in a now published study, Gerardo Ceballos of the University of Mexico and Paul Ehrlich of Stanford found that entire lineages are also disappearing, in what they call “mutilation of the tree of life.”

“In the long term, we are making a huge contribution to the evolution of life on the planet,” says Gerardo Ceballos, warning that it will cause “a lot of suffering for humanity” this century.

Paul Ehrlich, taking a different approach, emphasizes that man’s actions cause him to lose the only known living companions in the entire universe.

The two researchers used databases from organizations such as the International Union for Conservation of Nature and Birdlife International and studied 5,400 genera of land vertebrates, covering 34,600 species.

And they came to the conclusion that since the 15th century, 73 genera of land vertebrates have become extinct, with birds suffering the greatest losses, with 44 genera becoming extinct, followed by mammals, then amphibians, and then reptiles.

Based on historical rates of extinction of mammalian genera, those responsible estimate that the current rate of extinction of vertebrate genera is 35 times the rate of the last million years.

In other words, without human influence, the Earth would have lost only two species during that period. In five centuries, human actions have destroyed genres that would have taken 18,000 years to disappear without them.

“As scientists, we must be careful not to become alarmists,” says Gerardo Ceballos, adding that the seriousness of the discoveries requires “stronger statements than usual.”

“It would be unethical not to explain the scale of the problem because we and other scientists are alarmed.”

The official explains that on many levels, genera extinction is more serious than species extinction because when a species goes extinct, another member of the same genus can fill that role in the ecosystem. From the perspective of the tree of life, it is as if one branch fell and others branched out around it.

The worst thing, he adds, is when entire branches (genus) fall, “leaving a huge hole in the tree canopy” that could take millions of years to fill.

“Humanity cannot wait that long to restore its life support systems,” since “the stability of our civilization depends on the services provided by the Earth’s biodiversity,” he emphasizes.

Gerardo Ceballos gives the example of Lyme disease (transmitted by ticks) being on the rise: White-footed rats, the main carriers of the disease, used to compete with passenger pigeons for food, and with their disappearance, the rat population and cases of the disease increased.

In this case, we are talking about the extinction of one species, but the mass extinction of species could mean a proportional explosion of disasters for humanity, warns the person in charge.

To avoid further extinctions and subsequent social crises, two researchers are calling for immediate political, economic and social action on an unprecedented scale.

Conservation efforts, they say, should be a priority in tropical regions because they have the highest concentration of extinct genera and genera, with only one species remaining.

According to the system of organization of living beings, a species is defined as a group of organisms capable of reproducing and giving rise to new creatures, and a genus is a collection of species.