Scientists Warn that Sixth Mass Extinction Has 'Probably Started'

Over the past 450 million years, life on Earth has been devastated by at least five mass extinctions, which are typically defined as catastrophes that wipe out more than 75 percent of species in a short amount of time. Many scientists have proposed that we are entering a Sixth Mass Extinction, this time driven by human activity, though debates still rage over the validity and consequences of this claim. From a report: Now, a team led by Robert Cowie, research professor at the University of Hawaii's Pacific Biosciences Research Center, argues that 'the Sixth Mass Extinction has begun on land and in freshwater seems increasingly likely,' according to a recent article published in Biological Reviews. 'We consider that the Sixth Mass Extinction has probably started and present arguments to counter those who would deny this,' said the team, which also included biologists Philippe Bouchet and Benoît Fontaine of the Museum National d'Histoire Naturelle in Paris, France, in the article.

'Denying it is simply flying in the face of the mountain of data that is rapidly accumulating, and there is no longer room for skepticism, wondering whether it really is happening,' added the authors. Cowie and his colleagues refer to a multitude of studies cataloging the extinction of species across clades, but the article is primarily built around their research into mollusks, an invertebrate family that includes snails, clams, and slugs. This focus counteracts the disproportionate attention that vertebrates, such as birds and mammals, receive in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, among other conservation efforts.

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