The argument that plant and animal species are disappearing at a rapid rate from the earth has gained a new, eloquent voice through a lengthy article in the influential Harper’s magazine. However, he fails to persuade the careful reader.
David Quammen, author of the 10,000-word “Planet of Weeds: Tallying the losses of Earth’s animals and plants” in the October issue of Harper’s, writes, “The consensus among conscientious biologists is that we’re headed into another mass extinction, a vale of biological impoverishment commensurate with the (Ordovician, Devonian, Permian, Triassic and Cretaceous extinctions hundreds of millions years ago). Many experts remain hopeful that we can brake that descent, but my own view is that we’re likely to go all the way down. . . . Wildlife will consist of pigeons, coyotes, rats, roaches, house sparrows, crows and feral dogs.”
One characteristic of this impoverishment (and also a factor behind it) is the invasion of native species by exotic species, which he calls “weeds.” These “weedy species” are animals and plants such as zebra mussels, Asian gypsy moths, tamarisk trees, kudzu, and boll weevils — species that invade an area, establish themselves, and are hard to get rid of.
Such invasions constitute a genuine problem, worthy of study. However, they don’t necessarily imply ecological disaster, and Quammen doesn’t provide convincing evidence that they will. Instead, he wraps this interesting topic inside a shroud of lamentations about all kinds of trends and problems, including land conversion, population growth, overconsumption, and poverty.
When he writes about subjects he has extensively explored, he can be brilliant, as he was in his 1996 book, “The Song of the Dodo.” But in the Harper’s article, he lacks the grounding in his own experience that makes his writing persuasive, and he goes seriously off-course.
Quammen’s skill with words obscures figures that don’t add up. Reviewing claims that species are being rapidly extinguished, he cites the work of Norman Myers, one of the first people to claim that hundreds of thousands of species were in danger, and extinctions accelerating. Myers recorded a total of 75 species known to have been lost between 1600 and 1900, and another 75 lost between 1900 and 1979. Regrettable as those are, Quammen goes on to say that this figure of 75 species lost between 1900 and 1970 represents “a rate well above the rate of known losses during the Cretaceous extinction.” The Cretaceous extinction millions of years ago, he told us earlier, wiped out 76 percent of all species. How 75 species today can represent over 76 percent of all identified species (1.4 million as of 1991, according to Paul Ehrlich and E.O. Wilson), I do not know.
My guess is that this is some kind of proofreader’s error, but it suggests that the article is unreliable.
Even forgetting such a ludicrous claim, the article is one-sided. Quammen states that the “consensus among conscientious biologists is that we’re headed into another mass extinction.” Yet even the person chosen as the centerpiece of his article, University of Chicago biologist David Jablonski, doesn’t explicitly take that position in the article. Interviewed because of his “willingness to discuss the notion that a sixth [mass extinction] is in progress now,” Jablonski is clearly worried about the proliferation of “weedy species,” but he also thinks that human beings may adjust and change the trend.
To support the “chorus of consensus” that we are headed toward a mass extinction, Quammen cites three studies. All are predictions of future extinctions (not descriptions of current ones) based on studies of habitat loss. The predictions reflect the theory known as “island biogeography,” which relates the size of habitat loss to the number of species lost. Yet one prominent scientist, Lawrence B. Slobodkin (writing in the scientific journal Nature) has called this theory “useless for explaining or predicting actual cases.”
No one denies that loss of habitat can extinguish species, or that tropical deforestation is troubling. However, well established evidence that Quammen chooses to ignore suggests that the loss of species is smaller than his article proclaims. In their book “Noah’s Choice,” Charles Mann and Mark Plummer reviewed the evidence of actual, known extinctions. They pointed out that when Puerto Rico was nearly completely stripped of forest, only seven of the island’s 60 species of birds disappeared. And they reported that during the 19th Century, when the United States forest was extensively logged east of the Mississippi and around the Great Lakes, only five birds went extinct.
A 1992 book published by the World Conservation Union, “Tropical Deforestation and Species Extinction,” concluded: “Despite extensive inquiries, we have been unable to obtain conclusive evidence to support the suggestion that massive extinctions have taken place in recent times as [Norman] Myers and others have suggested.”
What Quammen fails to recognize is that humans don’t just harm their environment, they protect it and restore it. Quammen sees land conversion as a process that always leads toward biological impoverishment. Land begins as “wildlands,” he explains, and moves in a downward spiral toward the “degraded” state, which he describes as “abused beyond value to anybody.”
Yet this is not necessarily true. The forests of New England, which regrew naturally after farming declined, illustrate an opposite movement, toward wildness, not away from it. In the 1880’s, 50 percent of New Hampshire was forested. Today the figure is 86 percent.
By Quammen’s own report, 6.3 percent of the earth’s land area is officially protected as nature preserves or refuges. In the United States, a growing amount of wilderness areas have been set aside over the past 30 years. It is likely that as other countries also become more wealthy and can devote more land to preservation, public policy will move toward creating more protected areas.
And as farming becomes more technically advanced, it will require less space, allowing more land to return to wildness.
Furthermore, around the world, organizations such as the Nature Conservancy are actively purchasing and setting aside wildlands, and restoring those that have been abused.
“Weedy species” are not being ignored. Quammen observes that ecologist Daniel Simberloff has founded an institute to study invasive biology. He cites this as a sign of the plunge toward biological impoverishment, yet it is also a sign that human beings aren’t just lamenting the problem. They are addressing it.
I could go on. There is a multitude of evidence out there. Some of it does support Quammen’s worries, but plenty of it does not. Interestingly, Quammen criticizes the late Julian Simon for pointing out that the prevalent extinction estimates were pure guesses. Quammen complains that Simon used “the inexactitude of the numbers to cast doubt on the reality of the problem.”
Somehow, Quammen feels that he already knows the reality of the problem, and only the details are missing. But the evidence he cites is only part of the picture and therefore it is not persuasive.
Jane S. Shaw is a Senior Associate of PERC (the Political Economy Research Center) in Bozeman, Montana, and co-author with Michael Sanera of “Facts, Not Fear: A Parent’s Guide to Teaching Children about the Environment” (Regnery Publishing, Inc.).