The Sixth Extinction: A Seneca Cliff in the Making

To date, the majority of extinction studies have been biased towards terrestrial species and charismatic megafauna and we know relatively little about changes in the abundance and ranges of the shelly marine invertebrates that would provide a direct link to mass extinctions in the fossil record.

From custodians of deep time, we need quantitative assessments of the fossil record of the present and future earth in order to accurately size up current biotic changes with the same filter through which we see the past.

 Although extinctions are rare, the ecological ghosts of oceans past already swim in emptied seas.

You see the point? So far, we have focussed on the extinction of "charismatic" species, from the past one of mammoths, giant sloths, and the like to the ongoing ones of Elephants, tigers, cheetahs, and others. However, a true mass extinction sees the disappearance, or at least the the near disappearance of common species such as marine invertebrates. But that doesn't appear to be happening, yet.

There follows that, if someone in a remote future were to examine the fossil record for our times, he/she/it wouldn't see, not yet at least, the same kind of disastrous "Seneca Collapse" of the most common species that we see for the "big five" mass extinctions. Once a true "End-Permian-like" extinction were to start, it would be so rapid and destructive that nobody would be alive, discussing it.

That's it, folks: the title "We are NOT in the sixth mass extinction" simply means "we are not YET in the sixth mass extinction", but there are plenty of ongoing extinctions that prefigurate a true mass extinction ("emptied seas") for a non-remote future. That's because we know that most of the past mass extinctions (and perhaps all of them) were caused by the same phenomenon that's ongoing nowadays: the release of large amounts of greenhouse gases in the atmosphere.

Said in other words, imagine you are falling from the 10th floor. You are not yet splattered on the sidewalk and, if you really want to be precise, you shouldn't say that you are in the same condition of other people who fell from the same window in the past. Who knows? You might fall on something soft, or maybe learn how to fly while en route. Precision is precision, right?

So, the position taken by Dr. Erwin is scientifically correct, although it doesn't change what we know about the ongoing extinctions (and, as a personal opinion, I normally avoid branding the work of my colleagues as "junk science," even though I may not agree with them). We didn't go through a mass extinction, yet, because it is just beginning. The problem is that the meaning of the article in The Atlantic, and in particular its title, will NOT be generally understood. On the contrary, it will give plenty of ammunition to the throngs of those who claim that "CO2 is plant food," "the Earth is getting greener," "global warming is good for people"; and the like. It is already happening. As usual, when scientists say something that some people judge unpalatable, they are cheaters and liars. When a scientist says the opposite, he is suddenly defined as reliable.

I don't think Erwin is to be faulted in particular for this disaster in scientific communication. It happens all the time and especially when you stumble on journalists who tend to sensationalize what you tell them. Unfortunately, as scientists, we haven't yet learned how to communicate science to the public.