SP: There are people who believe that the claims that people -- like Ed Wilson, and Paul Ehrlich, and Norma Myers and myself -- have made about high extinction rates are so many doomsday myths. To answer those people, all we need is our own experience.

In the fossil record, we know that extinctions have gone on for millions of years. The dinosaurs are no longer here. But if we look at how often those historical geological extinctions happened -- how frequently they happened -- they happened at a rate that we can translate into very easy-to-understand terms.

There are about 10,000 species of birds on the planet at the moment. If those species were going extinct at a geological rate, we ought to see one extinction about every 100 years. In other words, it ought to be, at best, a one-in-a-lifetime event. I have seen species that are now extinct -- several of them -- extinctions that I have known and hated. It's not hard to go around the world and say good-bye to about one or two or three species per year. That very immediacy of those extinctions -- of birds that we know very well -- tells us that the current extinction crisis represents an extinction rate that must be at least 100 times what it ought to be.

Q: Chief role of humans in causing extinctions.

SP: The ultimate cause of this greatly increased extinction rate is us -- the fact that our population is so numerous, and the fact that our technology is increasing at a rate that we now have the capacity, for example, to chop down tropical forests at an extraordinary rate. That first factor of habitat loss -- of destroying areas that are the only homes for millions of species -- is one of our principal effects upon the biological heritage of our planet. It's not the only cause, however. We also moved a lot of species from where they should be to where they are now, and these introduced species -- some of them are relatively benevolent.

A hundred years ago, public-spirited people in New York wanted all the birds of Shakespeare in Central Park, and we have house sparrows and starlings as a consequence -- but some of species are devastating. I've had the experience of working on the island of Guam -- in the Marianas south of Japan, north of New Guinea. Guam has become Rachel Carson's nightmare of A Silent Spring. Go into the forests of Guam and there are no birds singing in the woods there. The cause in that particular case was an introduced snake, called the brown tree snake, that eliminated every last species of bird from the island or Guam. It's a very depressing to be if you happen to like birds. That carelessness, which is preventable, has cost us the lives of a lot of interesting, and fascinating, and economically important species.

Q: Any points raised worth your further deliberation?

SP: There's one idea that's so important, that even if it's not new to me, I'd like to share with you. That is the fact that in the Pacific alone, the body count that comes from looking at how the Polynesians exterminated bird species as they swept across the Pacific -- that total body count comes to somewhere between 1 and 2,000 species of birds. That's 10 to 20% of all the world's birds. So we are already capable of having an enormous impact. Even Stone Age cultures can have an enormous impact on the planet. And that means that our technological advanced cultures can have an even more devastating impact. That's not new, but I think everybody who looks at the fossil record -- the recent fossil record -- needs to understand that salient feature.

Of the things that I heard at this meeting, I think one of the interesting problems is the fact that paleontologists sometimes seem puzzled by the fact that these species' extinctions take a while to happen. You know, some species linger longer. What does that tell us? Well, I think there are good reasons to expect that some species will persist a long time before they finally go, but there are obvious policy implications for that. A lot of species that are now rare may be effectively doomed to extinction unless we are able to do something very difficult to keep them alive, to allow them to persist. Or maybe even, in some cases, to restore the habitat, to restore the ecosystems on which they depend, and so give them a viable future.

So what we see now may already have doomed very, very large numbers of species, and that's with just the five billion of us on the planet, not the 10 or even 20 billion of us that there is going to be by the middle of next century.

Q: Some hope of stemming current tide of extinction?

SP: Yes. I do believe there is hope. I think we understand the nature of the problem -- both its magnitude and its importance to us. I think increasingly we are becoming aware of how valuable species are to us. They are valuable in the simplest economic terms, as sources of medicines, sources of genes for agricultural crops....

They are important as sources of medicines, and genes for our agricultural crops. We also appreciate them. We spend an enormous amount of money worldwide on ecotourism, and they are important for ethical and religious reasons. A large number of different religions, religious groups, over the last few years have come out with very strong statements, indicating that it is simply wrong -- it is a sin, if you like -- to drive so many species to extinction.

But in addition to valuing species, we also now have a good indication of where -- precisely where -- those species are going to become extinct ... the hot spots of biological richness. Once we've identified those, we do have a hope of protecting them. It doesn't mean to say we have the money or the *willpower, but, increasingly, we're having the scientific knowledge that allows us to draw lines on maps -- a line in the sand, if you like, metaphorically -- that says: If we lose these places, we're going to lose a lot of the planet's biological heritage.

plenary address | abstract | bio