Are We in a Sixth Mass Extinction?

Amphibian Extinction 2007

In 2007, I published a manuscript in Journal of Herpetology that established a paradigm shift in how we discussed the expanding losses of amphibians on the global scene. Until this time, discussions referred to the phenomena as "amphibian declines" or "amphibian population declines. However, this manuscript demonstrated that the losses of amphibians in modern times far exceeded any disappearances of these organisms in the fossil record. Hence, the paradigm shifted from discussing amphibian declines and reframed discussions as amphibian extinction, because the these were not mere losses in isolated areas, but the rapid loss of this entire taxonomic class of organisms. The following year, David Wake and Vance Vredenburg released an article in PNAS questioning whether these results were an alarm bell that we could be entering a sixth mass extinction. Discover Magazine listed it as the fourth most important paper on amphibian die-offs.

McCallum ML (2007) Amphibian Decline or Extinction: Current Declines Dwarf Background Extinction Rate. Journal of Herpetology 41:483 - 491.

Vertebrate Extinction 2015

By 2015, this manuscript was finally published. The rapid updates in IUCN data kept requiring major updates to the calculations before it could get through peer review. Initially, it went under the radar, having been released just ahead of the Pope's encyclical addressing the environmental responsibilities of Catholics, which dominated the news circuit. However, immediately afterwards, Gerardo Ceballos, Paul Erlich, Anothony Barnosky and several other authors released a similar manuscript in the journal Science Advances. This caused my article, released just one month earlier, to emerge from the shroud of the Pope! Mongabay covered both articles simultaneously. Then, Stuart Pimm also released an article in the same thread. By the end of 2016, these three different pods of researchers had addressed the same data using different methods and assumptions, and concluded the very same thing. If humanity does not act soon, we certainly will face a sixth mass extinction. Are we in one? That is something that can only be evaluated after-the-fact.

McCallum ML (2015) Vertebrate biodiversity losses point to sixth mass extinction. Biodiversity and Conservation 25:2497 - 2519.

Turtle Extinction 2021

Turtles are a group of lower vertebrates whose systematics has moved them around in the tree of life. There unique characteristics made addressing whether their recent losses were as catastrophic as reptiles and other groups. After analysis, it was determined that indeed, extant turtles are disappearing faster than at anytime in history. Essentially, they are another indicator that if we do not start taking biodiversity losses seriously, our end may be nearer than we would like to believe.

McCallum ML (2021) Turtle biodiversity losses suggest coming sixth mass extinction. Biodiversity and Conservation 30:1257 - 1275.