The five previous mass extinction events in our planet’s history were all triggered by catastrophic natural phenomena, but according to the authors of a new study, a sixth huge die-off is currently underway, and this time, people are to blame.
The researchers, writing in the journal Biological Reviews, estimate that up to 13% of all invertebrate species may have gone extinct in the previous 500 years, and warn that it is now up to humanity to take action to avert a catastrophic loss of biodiversity. The International Union conceals the true scale of the current crisis, according to the authors, for Conservation of Nature’s (IUCN) Red List of Threatened Species, which creates the impression that the current pace of species loss is comparable to the background rate.
The researchers add, “However, the Red List is severely prejudiced.” “Almost all birds and mammals have been examined against conservation criteria, but only a small percentage of invertebrates have been evaluated.” “Taking into account estimates of the true number of invertebrate extinctions leads to the conclusion that the rate far exceeds the background rate and that we may be witnessing the beginning of the Sixth Mass Extinction,” they write.
To back up their claim, the researchers cite a 2015 study on mollusks that found that about 7% of terrestrial snail species have gone extinct since 1500. According to the researchers, between 7.5 and 13% of the two million known mollusk species have now vanished, assuming that this figure represents extinction rates for all non-marine invertebrates and that such species outnumber marine invertebrates by around three to one.
In absolute terms, this translates to between 150,000 and 260,000 extinctions, which are much more than the Red List’s 882 extinct mollusk species. Despite the fact that this conclusion is based on a “bold assumption” that has yet to be properly tested, the researchers conclude that a sixth mass extinction event “has unquestionably begun, and is being triggered by human actions.” While this remark may look alarmist, the authors go on to say that, there is no evidence that marine species harmed in the same manner that land-based invertebrates are, and that plants appear to be immune to the current crisis.
According to study author Robert Cowie, “we are the only species capable of changing the biosphere on a global scale,” and “we are the only species that has conscious choice about our destiny and that of Earth’s biodiversity.” The researchers reject the premise that our activities and their repercussions are just part of the natural evolution of life on Earth. “Denial of the issue, acceptance without reacting, or even supporting it represents an abrogation of humanity’s common responsibility and prepares the path for Earth to continue on its dismal track towards a Sixth Mass Extinction,” Cowie warned.