In pictures: World undergoing ‘sixth mass extinction’
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Animal species are disappearing at a rate not seen since dinosaurs vanished 66 million years ago, a new study has found, in what researchers say is the sixth mass extinction event in Earth’s history and one caused largely by humans.
The findings of the study, published in the journal Science Advances on Friday, could have serious implications for humans who may soon find themselves on the list of species under threat, its authors warned.
“If it is allowed to continue, life would take many millions of years to recover and our species itself would likely disappear early on,” said lead author Gerardo Ceballos of the Universidad Autonoma de Mexico.
The study, which also involved experts at Stanford University, Princeton University and the University of California, Berkeley, took extinction rates from the past 100 years and compared it to a “background rate” of extinction – the average number of species that went extinct in centuries “before human activity dominated” the planet.
In contrast to previous studies, researchers used what they described as “extremely conservative” figures for their analysis.
They assumed a background rate of extinction of two mammals per 10,000 species per 100 years – which they said was twice as high as previous widely used estimates.
This was then compared to the number of species declared extinct since the year 1900 using data compiled by the International Union for Conservation of Nature (IUCN). They did not include species that had been classified either “extinct in the wild” or “possibly extinct”.
‘Rapidly closing’ window
Even when using such cautious numbers, the researchers found that “the average rate of vertebrate species loss over the last century is up to 114 times higher than the background rate”.
A total of 198 vertebrate species have been lost since 1900, the IUCN’s data showed. Under normal circumstances, it would take between 800 and 10,000 years for such a large number of species to disappear, the study said.
“We can confidently conclude that modern extinction rates are exceptionally high, that they are increasing, and that they suggest a mass extinction underway the sixth of its kind in Earth’s 4.5 billion years of history,” said the researchers.
The causes of this mass extinction, they said, include habitat loss, overexploitation of natural resources and climate change, all of which are “related to human population size and growth”.
There is a “rapidly closing” window of opportunity to address the problem and a failure to do so could have serious repercussions for mankind, warned the scientists.
“Arguably the most serious aspect of the environmental crisis is the loss of biodiversity – the other living things with which we share Earth. This affects human well-being by interfering with crucial ecosystem services, such as crop pollination and water purification and by destroying humanity’s beautiful, fascinating, and culturally important living companions.”