The Earth may be on the brink of a sixth mass extinction, due to human activity, according to the academic journal Science.
The Earth's most recent mass extinction event occurred roughly 65 million years ago, when an asteroid wiped out 75% of all existing species, including the dinosaurs.
Commenting on the progression of Earth's present defaunation, or loss of species, Science author Sacha Vignieri said, "human impacts on animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance."
The team of biologists and ecologists who contributed to the study revealed that a third of all vertebrates on the planet are presently threatened or endangered. Vignieri cites "overexploitation, habitat destruction and impacts from invasive species" as ongoing threats, but warns that climate change due to human activity will emerge as the leading cause of defaunation. Likewise, diseases that come from pathogens introduced by humans have become a factor.
Paleoecologists estimate that modern man has driven approximately 1,000 species into extinction during our 200,000 years on the planet. Since the sixteenth century, man has killed off hundreds of animals, including the passenger pigeon and the Tasmanian tiger. According to the International Union for the Conservation of Nature, there are another 20,000 species threatened today.
Though, research has suggested that the widening extinction trend can be reversed.
Humans presently use half of the planet’s unfrozen land for cities, logging or agriculture. Reforestation and restoration of lost habitats, coupled with relocation and recolonization efforts can assist in the "refaunation" of species driven from their native locales.
Based on data published in Nature in 2011, it will take a century or two to assure another mass extinction event at the present rate of global depredation.
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