Population Extinctions versus Species Extinctions & the Time Factor of Determining the Seriousness of the Current Threats to Species

Population Extinctions versus Species Extinctions & the Time Factor of Determining the Seriousness of the Current Threats to Species. An article just published in the Proceedings of the National Academy of Sciences presents what they refer to as the “Sixth Mass Extinction” currently going on. The article is titled “Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines” and the authors are Gerardo Ceballos, Paul R. Ehrlich, and Rodolfo Dirzo.  The article makes a point that the number of species extinction in the past century may not seem large (estimated to be about 200 in the past century) but local populations of a large percentage of species have become extinct—the species exist in other locations but in these locations their numbers are also declining. Moreover, past major extinctions have taken millions of years so the 200 lost is actually very significant—given the rate of previous extinctions—the authors say that it should have taken about 10,000 years to lose that many species to extinction. The article is available online at: http://www.pnas.org/content/early/2017/07/05/1704949114.full.pdf