Sixth mass extinction may already be happening on Earth

The Earth may be going through its sixth mass extinction, but, unlike the previous ones, this one would be exclusively caused by human action. So says a new study led by the University of Hawaii, which considered a wide list of endangered species, including invertebrates — little considered in other analyses.

Life on our planet has already gone through five major extinction events, and although they were severe, they were all caused by natural events. But the new study, in addition to pointing out that the sixth mass extinction event has already begun, leaves no doubt about the human influence on this process.

On the left, the number of species cataloged and, on the right, the proportion of species on the red list of endangered species — invertebrates are little considered (Image: Reproduction/Robert Cowie et al.)

The study’s lead author, Robert Cowie, said the high rates of extinction and the reduction in the abundance of biodiversity are all well documented. “But some deny that these phenomena represent a mass extinction,” he added.

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According to Cowie, this denial is based on a tendency to face this crisis only for the species of mammals and birds, but when considering the invertebrates in the account — which make up the majority of biodiversity — the scenario is even more serious.

Using historical data on species of land snails and slugs, the researchers calculated that, since 1500, the planet has already lost 7.5% to 13% of the 2 million species known to date — the equivalent of 150,000 to 260,000 organisms. .

Endangered species

For the authors of the study, including the invertebrates in the analysis was critical to confirm that, in fact, we are witnessing the beginning of the sixth mass extinction. They also highlighted that marine and terrestrial species are being affected in different ways.

Recently extinct mollusc species in Rurutu, one of the Austral Islands (Image: Reproduction/O. Gargominy/A. Sartori/MNHN)

Island species, such as those that live on the Hawaiian Islands, are more affected than those that inhabit the continents. Furthermore, for the authors, the rate of extinction of plants seems to be lower than that of terrestrial animals.

The researchers also said that initiatives have managed to preserve “more charismatic” species, leaving out many others. Really other initiatives are not enough to reverse the general trend of extinction initiated by the human species.

To deny the crisis and accept it without reacting — or even pushing it forward — Cowie said, is to relinquish the responsibility common to humanity. “And it paves the way for the Earth to continue on its sad trajectory towards a Sixth Mass Extinction”, he pondered.

The study was published in the scientific journal Biological Reviews.

Source: Biological Reviews, Via SOEST

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