A new review paper in Nature makes a stab an answering the question “Has the Earth’s sixth mass extinction already arrived?” In an apparent effort to satisfy a variety of audiences with different evidentiary and skepticism standards, Nature and the reviews authors, led by Anthony D. Barnosky of the University of California, Berkeley, offer a variety of phrasings.
First we have the paper’s abstract, which wraps up with:
Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.
Then we have this from further down (behind the paywall):
Although there are many definitions of mass extinction and gradations of extinction intensity, here we take a conservative approach to assessing the seriousness of the ongoing extinction crisis, by setting a high bar for recognizing mass extinction, that is, the extreme diversity loss that characterized the very unusual Big Five (Table 1). We find that the Earth could reach that extreme within just a few centuries if current threats to many species are not alleviated.
The journal’s editors present this summary:
Palaeontologists recognize five major extinction events from the fossil record, with the most recent, the Cretaceous mass extinction, ending some 65 million years ago. Given the many species known to have disappeared in the past few thousand years, some biologists suggest that a sixth such event is now under way. Barnosky et al. set out to review the evidence for that claim, and conclude that the recent loss of species is dramatic and serious, but not yet in the mass extinction category — usually defined as a loss of at least 75% of Earth’s species in a geologically short time frame. But that said, there are clear indications that the loss of species now classed as ‘critically endangered’ would soon propel the world into its sixth mass extinction.
Carl Zimmer, in the New York Times, provides this take:
If endangered species continue to disappear, we will indeed experience a sixth extinction, over just the next few centuries or millennia.
The Berkeley scientists warn that their new study may actually grossly underestimate how many species could disappear
Zimmer then launches into a comprehensive exploration of the question of whether or not we can blame these looming extinctions on global warming. Opinions are divided on the cause, we learn, although there is a consensus that we’re losing biodiversity. There’s also the reality that some species will be able to adapt to whatever changes are in store for the climate, while others will be replaced.
For me, the take-home message is change is inevitable. One can argue that change in of ifself is neutral. Could be good, could be bad. Depends on what kind of change you’re talking about. But given 1) how dependent the human species is on the way the ecosystem works now — think of the hundreds of millions of people who rely on protien from the ocean, for example — and 2) how long it takes ecosystems to restore their productivity levels, rapid and extensive change is unlikely to be good for us. It would be foolish to assume that the consequences will be anything but consequential.
It’s not just a matter of making a new plan, Stan.