Last week the science fiction pop-culture blog io9 published an article asking the question, are we in the middle of a mass extinction? To answer that question, they interviewed Ross MacPhee, a paleontologist, curator at the American Museum of Natural History, and an expert on mass extinction. You can read that article for yourself, but in brief, he argued that we are not in the middle of a mass extinction event because 1). in order for it to be a mass extinction you have to lose species from every level of the biosphere, from top predators to micro-flora, and 2). statistical estimates of the modern loss of species based on E. O. Wilson’s work have not been put to empirical test. Furthermore, loss of local populations of animal and severely reduced populations of species do not equate actual extinctions.
There’s no reason to doubt MacPhee’s expertise. He’s had a long and esteemed career, and contributed significantly to his discipline. However, it’s important to remember that by discipline he is a paleontologist. As such he is an expert in past extinction events, not current or future events. Asking a paleontologist about a current extinction event is a little like asking a sports historian to predict next year’s Super Bowl. The beginning of a mass extinction event is probably going to look a lot different from the middle. The truth is, we can’t know if we’re in the middle of a mass extinction event until we’re in the middle of a mass extinction event, and by then it’s too late.
So instead of looking at what is happening now, and measuring it against a hard-coded definition, it would probably be more helpful to ask ourselves, “are things happening now which left unchecked could result in a mass extinction?”
News of one such mass-extinction precursor came across my feeds today. An article in Nature by Siegel and Franz suggests that our current level of climate change is resulting in about a 1% a year drop in the population density of phytoplanktons, the bottom-most element of the marine food chain. Specifically, they note a 40% decrease in population from 1950 to the present. While MacPhee’s assessment that it’s not a mass extinction until species at the top and bottom of the biosphere have been effected, it doesn’t take much of an intuitive leap to say that if the thing that krill feed on goes extinct, or at very least is driven to the brink of extinction, a lot of other species will disappear too. So, while I don’t fault MacPhee for answering the question asked of him, I do think that there was a more responsible way of answering it than this, “My point is that people are speculating about extinction with arm-waving. I don’t see evidence of mass extinction or extinctions of large effect. Doubtless humans are endangering species – but how many gravestones are we talking about? I don’t know, and I don’t think anybody else does either.” As he notes earlier, when extinctions happen, they happen quickly. Otherwise life has a chance to adapt. By the time we can show him the cemetery, we’ll be living in it. So the best question is not, “Are we living through a mass extinction event” instead it is, “Are we doing everything we can to promote resiliency in the form of rich biodiversity while we can?”
Further Reading:
David A. Siegel & Bryan A. Franz. Oceanography: Century of phytoplankton change. Nature, July 28, 2010; p569
E. O. Wilson The Future of Life, 2002, Knopf, ISBN 0-679-45078-5
Those phytoplankton numbers really shocked me. I hadn’t realized how big the problem was before. I think the answer to your question is no. Now what?
Much of our response would be predicated in whether it was excess heat that was causing the die off, or some other factor of climate change. If it is heat, then steps to mitigate the stockpile of greenhouse gasses is the first priority. According to an upcoming article to be published in the Journal of Geophysical Research (Atmospheres) by Stanford professor of environmental engineering Mark Jacobson we should be focusing on the reduction of soot. Soot influences the way clouds, snow and surfaces store and release heat. Unlike CO2, soot gets washed out the the atmosphere quickly. So while it will take hundreds of years for CO2 levels to decrease, if we can start capturing soot at its production points, we can remove it as a factor from climate change. Jacobson’s models show that soot has more on an impact that methane on climate change, so it’s a significant contributor. It’s still a challenging technical problem, since a goodly fraction of the soot comes from wood and dung burning cook fires (and also from summertime charcoal BBQ grills, I’m guessing. ) It’s one thing to regulate factory and automobile soot, it’s another to keep destitute people from cooking and staying warm. Still, until carbon capture and real alternative fuel sources come on line, this is something we can do now that will make a difference.
Thanks for a rational appraisal of my interview with i09. The route to understanding of any phenomenon is through the brain, not the heart. I care as much about the planet and its contents as anyone does. I don’t care, however, for automatic, gut-level appraisals that merely repeat common knowledge without demanding supporting facts and figures–which is my entire point about perceptions of the current “mass” extinction. Leave cud-chewing of predigesta to the cow; think for yourself; demand answers to obvious questions.
Phytoplankton reduction is interesting and important. Question: To place the current reduction in perspective, were there reductions of equivalent magnitude at, say, the beginning of the Holocene or the end of the last glaciation? Could this be investigated with ocean-sediment cores? In other words, how good is the historical picture for one to be reasonably certain current climate change is the forcing mechanism? If flux is an important feature of the system, what is the amplitude historically? And so on and on. I don’t know the answer(s), but would like to see attention paid to this matter, because that permits a rational assessment of the finding’s importance.