According to a new study published in the journal Science Advances, Earth’s biota is entering a sixth ‘great mass extinction.’
Earth at night seen from space. Image credit: NASA.
There is agreement among researchers that extinction rates have reached levels unparalleled since the last ‘great extinction’ 66 million years ago when the dinosaurs perished. However, some scientists have challenged the theory, believing earlier estimates rested on assumptions that overestimated the crisis.
The new study, led by Dr Gerardo Ceballos from the Universidad Autónoma de México, shows that even with extremely conservative estimates, vertebrate species are disappearing up to 114 times faster than the normal rate between mass extinctions.
“If it is allowed to continue, life would take many millions of years to recover, and our species itself would likely disappear early on,” Dr Ceballos said.
Using fossil records and extinction counts from a range of records, Dr Ceballos and co-authors compared a highly conservative estimate of current extinctions with a background rate estimate twice as high as those widely used in previous analyses – two mammal extinctions per 10,000 species per 100 years.
Focusing on vertebrate species, the scientists asked whether even the lowest estimates of the difference between background and contemporary extinction rates still justify the conclusion that people are precipitating ‘a global spasm of biodiversity loss.’ The answer: a definitive yes.
“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 scientists wrote in the study.
Despite the gloomy outlook, there is a meaningful way forward.
“Avoiding a true 6th mass extinction will require rapid, greatly intensified efforts to conserve already threatened species, and to alleviate pressures on their populations,” the scientists concluded.
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Gerardo Ceballos et al. 2015. Accelerated modern human – induced species losses: Entering the sixth mass extinction. Science Advances, vol. 1, no. 5, e1400253; doi: 10.1126/sciadv.1400253
