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The Verge of Extinction
The Verge of Extinction
Stuart Pimm, Pew scholar and professor of evolutionary biology at UTK, is one of the leading authorities in the world on species extinctiona man who's made his mark quantifying the rate at which species go extinct so that we might better understand the impact of our own species on the world at large. Speaking over the phone from the Florida Everglades (where he's studying the extinction of a particular sparrow), he possesses some alarming statistics, and likes to start off all his interviews by laying them out:
"There are six billion people on the planet," he begins. "If you look at how much fresh water there isall the rivers and lakesthe six billion of us already consume 50 percent, half, of the available water each year.
"If you look at the annual new plant growth produced each year, which is sort of the interest in the world's biological savings account, humanity already consumes about 50 percent of that each year, too.
"If you look at the biologically useful part of the ocean, we consume about 30 percent of the annual plant growth there for our fisheries.
"So you have some sense from those four numbers of the sheer scale of global human impact. All of those are huge numbers. We're all aware that many people project that there will be 12 billion humans on our planet within a generation or so..."
He pauses then, leaving the listener to draw her own conclusionwhich is, in this case, that with this massive level of human impact, the planet will not be able to sustain life. And which, as it turns out, is exactly the case for approximately 40 percent of the species on earth.
"If you look at the rate of species extinctions, we are now driving species to extinction 1,000, or maybe even 10,000, times faster than you'd expect in the geological record," he says. "We know that species have always gone extinct, but the rate at which species are going extinct now is becoming 1,000 to 10,0000 times greater. As a consequence of that, I calculate that within the next few decades we might drive species to the point of extinction such that maybe 40 percent of all the species on the planet may be well on the path to extinction."
This is devastating, Pimm explains, comparable to the extinction event that wiped out the dinosaurs 65 million years ago. At that time, too, about 40 percent of the world's species were lost, and it took the planet 10 million years to recover its biological diversity. That was the fifth in a succession of prehistoric massive extinctions; what is happening on the planet right now, Pimm says, has all the hallmarks of the sixth.
"We're not sure of all the details of what happened then, but most scientists are now convinced that the last mass extinctionthe one that killed the dinosaurswas the result of a cataclysmic encounter with an asteroid," he explains, "just the sort of thing you'd see in movies like Deep Impact and all the rest. What we're saying now, of course, is that human impact is that big. What we're doing to the planet is broadly comparable to the kind of scenario that was elucidated by movies like Deep Impact. That's dramatic, but human impact is along that scale in total."
Already, he says, we've lost about 10 percent of our planet's species over the past 100 years. The reasons, he says are two: one, obviously, is the destruction of habitatsclearcutting the forests for example, and damming up rivers so that waters no longer flow. The second is introduced species, imported intentionally or accidentallythings like kudzu and zebra mussels (to name two that hit close to home) that cause harm when introduced to alien environments, and which tend to drive local species out of existence.
And the ramifications of losing another 40 percent over the next few decades, he says, are clear: "What we're doing now is to affect not only the lives of our children and our grandchildren, but absolutely countless generations to come. It's an ethical problema religious one if you like. I think there is a major ethical concern about destroying 40 percent of God's creation, if you like to put it like that. That we are making a huge impact upon the planet and natural heritage and resources and so on, and doing it for a very long time.
"For people who are unhappy with that connection, there is a clear economic connection. Biological diversity matters to us in a clear cash value kind of way," he says. "For one thing, nature provides a lot of ecosystem servicesthe services of cleaning fresh water, cleaning the air, reducing soil erosion. If you chop a forest down, you have massive soil erosion. If you lose your rivers, you don't have rivers cleaning up the wastes we put in them. There are all variety of ecosystem services like that that nature does for us that we take for grantedsince we don't have to pay for them, we don't worry about them. Those services that nature provides are hugely expensive to replace."
Other examples of economic impacts include the loss of potential miracle cures like the anti-cancer drug tamoxifen, which is extracted from the bark of the Western yew. "It was a tree that people thought was a trash treethat it didn't have any value. And then somebody comes along and discovers that it contains a remarkable anti-cancer drug. And it's not just that it's a potentially important cure for cancer, but that it's an anti-cancer drug that works in a dramatically different way. It's strange, it's bizarre, it's like nothing else we've ever seen before. Nature is full of bizarre chemical compounds like thatand you just never know what you're going to need next."
And thenand this strikes near and dear to Pimm's heartthere's the loss of aesthetic beauty that would, in particular, exact a huge toll in this part of the world. "Approximately 10 million people visit the Smokies each year," he says, "and they do it because it's a wonderful, beautiful place. The impact on our economy of that tourism is hugeand it's huge not just because of Pigeon Forge and Gatlinburg. We've flown into McGhee Tyson and walked past all the billboards, about one-third of which show forests. The reality is we are justifiably proud of the nice environment that we have and it's clearly of economic value to us. It's unlikely that we'd see posters advertising this region as a desirable place to visit or relocate your high-tech factory if instead of showing pictures of woodlands we were showing pictures of clearcuts."
The upshot is clear: "When we destroy biological diversity, we are sometimes making a really stupid economic decision."
The worst case scenario that Pimm sets forth is a grim one: "Worst case is 12 billion people, all making very short term, very foolish choices about what their futures will be. The ultimate conclusion would be that we could have a planet where only a few percent of the planet would be natural. That you would have a lot of small protected areas, postage-stamp areastiny parts where all you would see would be a shadow of the former variety of nature. There would be no lions and tigers and bears in the wild, they would only be in zoos. There would be no more wild."
Pimm is not a fatalist, however, despite the exacting toll of his workwhich has been, clearly, to measure the benchmarks of our planetary decline. "Is life in the U.S. going to come to an end? No. We'll continue to live very prosperous lives. But that's not to say those lives won't be poorer as a consequence.
"The good news is that it's not too late. As a society, we simply need to make sensible choices," he says, citing as an example the Endangered Species Act, which saved high-profile species like the American bald eagle, the peregrine falcon, and the gray whale from extinction. "Making the right choices is not merely a matter of sacrifice, it's a matter of weighing what the advantages and disadvantages are, and recognizing that some people have a short-term vested interest in destroying natural resources, and that we have to evaluate as a society whether we should let them do that."