The Sixth Mass Extinction

Humans have been significantly impacting upon extinction rates since approximately 2 million years ago, when one of our distant extinct ancestors switched from a primarily herbivorous diet to one which included increasing proportions of animal flesh (Turvey and Crees 2019).

With the further spread of humans across Africa in the late Pleistocene epoch, improvements in hunting methods, and a contemporaneous monumental shift in climate and environment, humanity lost species of megafauna and other larger vertebrates on a massive scale (Turvey and Crees 2019). The dawn of the Holocene about 11,700 years ago saw the further depletion of biodiversity by reason of human activities of settlement, urbanisation, industrialization, sea travel, and colonization (Turvey and Crees 2019). Specifically, in modern times, the rates of extinction have increased in tandem with the advent of industrialization in the past 2 centuries (Ceballos et al 2021).

There is substantial evidence supporting the argument that we are now living in a mass extinction event; the sixth in planetary history.

The number of vertebrate species extinctions between AD1500 and 1900, if they had taken place in accordance with the background rate, would likely have taken place over the course of many thousands of years instead (Ceballos et al 2021). A conservative estimate puts the number of extinctions since 1500 at 868 species, implying that the modern extinction rate is more than 100 times the background rate (Turvey and Crees 2019).

References:

• Ceballos, G., P.R. Ehrlich, A.D. Barnosky, A. Garcia, R.M. Pringle and T.M. Palmer. (2015). ‘Accelerated modern human–induced species losses: Entering the sixth mass extinction’, Science Advances 1(5) 2015.

• Turvey, S.T. and J.J. Crees. (2019). ‘Extinction in the Anthropocene’, Current Biology 29 2019, R982–R986.