A major but highly conservative study has found that the Earth’s sixth mass extinction event is underway, and if we don’t take action very soon, our own species is under threat.

“[The study] shows without any significant doubt that we are now entering the sixth great mass extinction event,” said Paul Ehrlich, senior fellow and Bing professor of population studies at Stanford’s Wood Institute for the Environment.

Published today in the open-access journal Science Advances, the study has found that even using highly conservative estimates, the rate of species extinction now is 100 times the background rate – the normal level of species extinction between mass extinction events.

41% of amphibian species and 26% of mammal species are currently under threat of extinction, and if these go, there will be a knock-on effect on other species that form part of the same ecosystem, as species and related resources essential to their survival disappear.

“There are examples of species all over the world that are essentially the walking dead,” said Ehrlich.

Eventually, this would stretch to humans, as despite our best efforts and fanciful notions to the contrary, we are still highly reliant on the resources the world provides for our own survival.

“If it is allowed to continue, life would take many millions of years to recover, and our species itself would likely disappear early on,” explained study lead author Gerardo Ceballos, from the Universidad Autónoma de México.

While it is generally agreed upon that species are going extinct at a higher rate than normal, some have previously questioned earlier estimates of the severity of the situation, and thus muddied the argument for action, claiming studies overestimated the issue.

However, the researchers in this new study believe their work lays this scepticism to rest, confirming that not only is a mass extinction underway, but that we have little time to stop catastrophic long-term damage from being caused.

In order to tackle the arguments of sceptics, the scientists worked with very conservative data, focusing on vertebrates, a group with the most reliable data available.

They used fossil records and extinction counts from a host of different sources to produce a highly conservative estimate of the current rate of extinction, comparing this to a background rate twice as high as is commonly used.

In other words, the number of species the study assumed to be going extinct was smaller than in many other studies, while the cut-off point where the rate of extinctions ceased to be considered ‘normal’ was far higher. And yet, they still found that a mass extinction was underway, and, with such conservative estimates, could be far worse than they project.

“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 research paper.

However, while the threat of mass extinction is clearly deeply concerning, the scientists were keen to stress that all was not entirely lost.

If a major conservation programme is initiated now, we can still prevent the worst from happening, although it will require drastic efforts.

“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,” said the authors in the paper.

But with the associated costs of such a programme – both in terms of direct expenditure and the cessation of other economically beneficial activities – likely to be high, the question of whether we will take adequate action in time remains doubtful.

Journal reference: Accelerated modern human–induced species losses: Entering the sixth mass extinction,” by G. Ceballos et al.