6ª extinción masiva en marcha
Homo sapiens provoca tasas de extinción equiparables a extinciones masivas
El Dr. Gerardo Ceballos, especialista mexicano de la UNAM, publica en Science Advances, con Paul Ehrlich, Tony Barnisky, Andrés Garcéa, Rod Pringle y Todd Palmer, las tasas de extinción actuales. De acuerdo con tasas de extinción durante grandes periodos geológicos, a los vetebrados que se extinguieron durante el siglo XX les hubiera tomado alrededor de 10 mil años para alcanzar su extinción. Es decir, vamos al menos cien veces más rápido debido a la intervención humana a escala de la biosfera.
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The oft-repeated claim that Earth’s biota is entering a sixth “mass extinction” depends on clearly demonstrating that current extinction rates are far above the “background” rates prevailing between the five previous mass extinctions. Earlier estimates of extinction rates have been criticized for using assumptions that might overestimate the severity of the extinction crisis. We assess, using extremely conservative assumptions, whether human activities are causing a mass extinction. First, we use a recent estimate of a background rate of 2 mammal extinctions per 10,000 species per 100 years (that is, 2 E/MSY), which is twice as high as widely used previous estimates. We then compare this rate with the current rate of mammal and vertebrate extinctions. The latter is conservatively low because listing a species as extinct requires meeting stringent criteria. Even under our assumptions, which would tend to minimize evidence of an incipient mass extinction, the average rate of vertebrate species loss over the last century is up to 100 times higher than the background rate. Under the 2 E/MSY background rate, the number of species that have gone extinct in the last century would have taken, depending on the vertebrate taxon, between 800 and 10,000 years to disappear. These estimates reveal an exceptionally rapid loss of biodiversity over the last few centuries, indicating that a sixth mass extinction is already under way. Averting a dramatic decay of biodiversity and the subsequent loss of ecosystem services is still possible through intensified conservation efforts, but that window of opportunity is rapidly closing.
- Sixth mass extinction
- vertebrate extinctions
- rates of extinction
- background extinction
- modern vertebrate losses
Science Advances 19 Jun 2015:
Vol. 1, no. 5, e1400253