Researchers have declared that the Earth is entering a mass extinction event, and that it is being caused by humans, but this is part of a much larger story.

A team at the Stanford Woods Institute for the Environment have published a study that says that we are entering a sixth great mass extinction event, where the current rate of species loss is over 100 times that of what would normally be seen. The study also says that this is what they consider to be a conservative estimate; that this rate the loss in biodiversity benefits to humans will be seen within three generations, and that 75 percent of Earth’s species could be lost within two generations.

"The study shows without any significant doubt that we are now entering the sixth great mass extinction event," says lead researcher Paul Ehrlich, Professor of Population Studies in biology at Stanford Woods.

"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. "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 study recommends, "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."

Past extinction events have tended to either happen very suddenly, such as the great Permian extinction, or to emerge more slowly, ending in a dramatic drop in species numbers, such as the extinction that destroyed the dinosaurs. More recently, a slow decline in species diversity on earth began 2.8 million years ago when the Central American land bridge rose out of the ocean and altered the currents that had been keeping Earth’s temperatures relatively stable for millions of years. Subsequently, for reasons that are still incompletely understood, the planet began to cycle into a period of ice ages lasting around a hundred thousand years, punctuated by interglacials that last around fifteen thousand years.

Transitions between these two states challenge species adaptations, with the emphasis on larger creatures which need a more extensive food supply over a broader range, such as the Wooly Mammoth, which suffered a catastrophic dieback when its forage disappeared between 15,000 and 10,000 years ago during the Younger Dryas. Similarly, mankind, whose food needs now demand vast agricultural space and a reliable climate, is vulnerable to climate change, and exquisitely sensitive to its dangers.

The present extinction event is following the same pattern as the Cretaceous extinction that brought the dinosauria to an end. For around 2 million years, changing climate had challenged the dinosaurs to ever more difficult adaptations. Then, either because of an enormous volcanic event or an asteroid strike, or both, the planet experienced a period of continental fires, extreme acidification of the atmosphere and a whole cascade of negative events that destroyed essentially all large species both on land and in the oceans.

We are not at the initiation of an extinction event at all, but in the early stages of its climax, which is, once again, being caused by negative changes in the atmosphere, specifically, a fantastic rise in the CO2 burden that is causing warming that will soon lead to vast releases of methane in arctic regions and a heat spike that will make much of the planet’s now-arable areas non-viable for crop production and lead to extensive reductions in the human food supply.

Avoiding an extinction climax is not only going to require dramatic reductions in human CO2 emissions, but also a recognition of the existence of the established climate cycle that suggests that the present interglacial is ending. In the past, they have ended with arctic melt, followed by a huge methane spike, a period of catastrophic heating and then, as the methane dissipates, equally catastrophic cooling. The same process is taking place now.