Mass extinctions during the past 500 million years rapidly removed branches from the tree of life and required millions of years for evolution to generate functional replacements for the extinct organisms. We are in the sixth mass extinction event. Unlike the previous five, this one is caused by a single species, Homo sapiens. Beyond any doubt, it is more severe than previously assessed and is rapidly accelerating. A duo of scientists from Stanford University and the Universidad Nacional Autonoma de Mexico now shows — by examining 5,400 vertebrate genera (excluding fishes) comprising 34,600 species — that 73 genera became since 1500 CE in what they call a ‘mutilation of the tree of life.’
Over the last century the pace of many human activities has so accelerated, and human overpopulation grown so severe, to have created a dramatic global environmental transformation.
Most natural ecosystems have been highly modified or have disappeared altogether, and the abundance of wildlife has been greatly reduced.
In well-studied major taxonomic groups, thousands of species and myriad populations have vanished.
The precise number of recent extinctions is impossible to know, but current animal species extinction rates are estimated to be hundreds or thousands of times higher than the background rates that prevailed for millions of years prior to the agricultural revolution.
Information on species’ conservation statuses from the IUCN, Birdlife International, and other databases has improved in recent years, which allowed Dr. Gerardo Ceballos from the Universidad Nacional Autonoma de Mexico and Stanford University’s Professor Paul Ehrlich to assess extinction at the genus level.
Drawing from those sources, the researchers examined 5,400 genera of land-dwelling vertebrate animals, encompassing 34,600 species.
Seventy-three genera of land-dwelling vertebrates, the authors found, have gone extinct since 1500 CE.
Birds suffered the heaviest losses with 44 genus…
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