Elizabeth Kolbert’s The Sixth Extinction is a highly readable, discursive review of the state of the biosphere in the Anthropocene — i.e., now. It’s aimed at a general audience and entertains as much as it informs, relating a wide variety of anecdotes, mostly derived from Kolbert’s travels and investigations while writing this book. I think it a very worthwhile book, especially perhaps as a present for those in your life who are skeptical about global warming or science in general. Not that Kolbert is a scientist or pretends to be one, but it offers an outsiders’ view of a fair few scientists in action, chronicling the decline of many species.
Kolbert’s report is necessarily pessimistic about the general prospects for a healthy biosphere, given that the evidence of species endangerment and decline is all around and she has spent some years now documenting it. But she tries to be as optimistic as possible. She points out a variety of successes in evading or mitigating other “tragedies of the commons”, such as the banning of DDT after Rachel Carson’s warning that our springs risked going silent. Or the prominent case of the missing (well, smaller) ozone hole.
On matters that are contentious within science, Ms Kolbert aims for neutrality. For example, what killed off the megafauna — such as the marsupial lion in Australia, cave bears and saber tooth cats in America, mammoths and aurochs in Europe — that was widespread prior to the presence of homo sapiens? One school suggests that climate change, say, in the form of retreating ice sheets, was the culprit. She points out that doubts arising from the fact that the extinctions of the megafauna occurred at quite different times and, indeed, in each case shortly after the arrival of humans, militate against climate change as a sole cause. The main alternative is, of course, that these are the first extinctions due to human activity, so that the Sixth Extinction began well before the industrial age. Kolbert points out that advocates for climatic causation criticize the anthropogenic crowd for having fallen for the post hoc ergo propter hoc fallacy. But neutrality on this point is a mistake. While correlation doesn’t strictly imply direct causation, it does strictly imply direct-or-indirect causation: Hans Reichenbach in The Direction of Time made the compelling point that if there is an enduring correlation between event types (not some haphazard result of small samples and noise), then there is either a direct causal chain, a common cause, or an indirect causal chain that will explain the correlation. Everything else is magic, and science abhors magic. Given that the extinctions and the arrivals of humans fit like a hand in a glove, it is implausible that there is no causal relationship between them. As sane Bayesians (i.e., weighers of evidence) we must at a minimum consider it the leading hypothesis until evidence against it is discovered. Of course, the existence of one cause does not preclude another (even if it makes it less likely); that is, climatic changes may well have contributed to human-induced extinctions in some cases.
On a final point Kolbert again opts for neutrality: does the Sixth Extinction imply our own? Can we survive the removal of so many plants and animals that the Anthropecene should be counted as one of the Great Extinction events? Will humanity’s seemingly boundless technological creativity find us a collective escape route?
I find the enthusiasm of some futurologists for planetary escape a bit baffling. The crunch of Global Warming will be hitting civilization pretty hard within 50 years, judging by anything but the most extremely optimistic projections. The ability to deal directly with Global Warming, and the related phenomena of overutilization of earth’s resources to support around 10 billion people at an advanced economic level of activity, is possibly within our grasp, but it is very much in doubt that we will collectively grasp that option. The ability to terraform and make, say, Mars habitable in a long-term sustainable way is not within our grasp and is not in any near term prospect. Simply escaping from our own earthly crematorium is not (yet) an option. If Elon Musk succeeds in reaching Mars, he will almost certainly soon thereafter die there.
The situation on earth isn’t so dissimilar. If Global Warming leads to massive agricultural failure, the watery entombment of half the major cities on earth, unheard of droughts, floods and typhoons, resource wars and human migrations, the strain on the instruments and processes of civilization is reasonably likely to break them. If civilization comes undone, it will be impossible to avoid massive starvation and societal collapse. The dream of some to wait it out in a bunker and emerge to a new utopia thereafter is about as likely as the descendants of Musk building a new civilization on Mars. Whether the extinction of civilization entails the final extinction of humanity is a moot point. But human life after civilization will surely be nasty, brutish and short.
The best alternative is to put a stop to Global Warming now, and use the energy and human resources that effort saves to solve the remaining problems of resource depletion, habitat destruction and human overpopulation. That requires a sense of urgency and a collective will so far absent.