Earth is entering a mass extinction that threatens humanity’s existence, researchers have declared. A team of American scientists claim that their study shows “without any significant doubt” that we are entering the sixth great mass extinction on Earth.
The study says that species are disappearing at a rate 100 times faster than would normally be expected – and that is a conservative estimate.
And such a catastrophic loss of animal species presents a real threat to human existence, the experts warn, as crucial ecosystem “services” such as crop pollination by insects and water purification in wetlands is also put at risk.
At the current rate of species loss, humans will lose many biodiversity benefits within three generations, according to Paul Ehrlich, the Bing Professor of Population Studies in biology and a senior fellow at the Stanford Woods Institute for the Environment, who led the research. “We are sawing off the limb that we are sitting on,” Prof Ehrlich said.
The study warns that humans are are precipitating “a global spasm of biodiversity loss” – and that the window for conserving threatened species is rapidly closing.
Prof Ehrlich said, “The study shows without any significant doubt that we are now entering the sixth great mass extinction event.”
The study, published in the journal Science Advances, shows that even with extremely conservative estimates, species are currently disappearing up to about 100 times faster than the normal rate between mass extinctions, known as the background rate.
“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 Autónoma de México. The authors fear that 75 per cent of the species on Earth today could be lost in just two generations’ time.
“We emphasize that our calculations very likely underestimate the severity of the extinction crisis, because our aim was to place a realistic lower bound on humanity’s impact on biodiversity,” the researchers write.
Since 1500, more than 320 terrestrial vertebrates have become extinct. Populations of the remaining species show a 25 percent average decline in abundance, and the situation is similarly dire for invertebrate animal life. Across vertebrates, 16 to 33 percent of all species are estimated to be globally threatened or endangered.
Large animals – described as megafauna and including elephants, rhinoceroses, polar bears and countless other species worldwide – face the highest rate of decline, a trend that matches previous extinction events.
Human population growth, per capita consumption and economic inequity has altered or destroyed natural habitats, the researchers say. They said the main impacts were land clearing for farming, logging and settlement, the introduction of invasive species, carbon emissions that drive climate change and ocean acidification, and toxins that alter and poison ecosystems.
Ehrlich and his colleagues do offer some hope. “Avoiding a true sixth mass extinction will require rapid, greatly intensified efforts to conserve already threatened species, and to alleviate pressures on their populations – notably habitat loss, over-exploitation for economic gain and climate change.”
Ceballos added: “I’m optimistic in the sense that humans react – in the past we have made quantum leaps when we worked together to solve our problems.” The researchers hope their work will inform conservation efforts, the maintenance of ecosystem services and public policy.