Why So Many Species? The Factors Affecting Biodiversity 
Why So Many Species? The Factors Affecting Biodiversity
by Yale / Stephen C. Stearns
Video Lecture 31 of 36
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Date Added: November 6, 2009

Lecture Description

One can look at biodiversity from several perspectives. An ecological point of view tries to determine how necessary diversity is for an ecosystem to function. An economic point of view tries to capture the value of the "services" nature provides for mankind. An evolutionary point of view shows how artificial the human "right" to dominance is. Finally, a personal point of view captures the emotional basis for the values that humans place on biodiversity.

Reading assignment:

Cotgreave, Peter and Irwin Forseth. Introductory Ecology, chapter 14


April 13, 2009

Professor Stephen Stearns: Now today I am going to talk about biodiversity and whether or not it's something we should be worried about, and how to think about things like the extinction crisis which is being caused by human activity.

And I don't want you to forget this extremely simple idea here, that the impact of humans on the environment basically is a function of how many people there are on the planet, times the average amount that each of those people consumes, multiplied perhaps by some fudge factor to express good or bad behavior on the part of the humans. And I think that the Greeks probably could have written that down 2500 years ago. It's pretty straightforward. It's nothing that is particularly surprising.

Nevertheless it is striking to me that this half of the equation, the upper half of the equation, which is the population problem, has pretty much disappeared from public discourse on this issue, and I think it's a result of pushback from various groups that see any discussion of the population problem as inevitably involving contraception or abortion, which for some groups has religious issues.

And it's also a pushback from the poor countries of the world, against the rich countries, saying, "You can't come down here and tell us what to do after you've all gone and screwed up your own environment. Let us get on with our own lives, and that's not our priority." Nevertheless, in the long-term, that's true. The impact of humans on the environment of the planet is basically a function of how many people there are on the planet times how much they're using. And we can't get away from that.

You will find in the literature on things about biodiversity problems, extinction problems, an awful lot of fairly refined, scientific analysis. You will find people applying cutting edge ecological theory to the issue. But, by way of introduction, I never want you to forget that the problem of human impact on the other species on the planet is not a problem that we can really solve with scientific research. We can only solve it by understanding the incentives that people encounter to have more babies, or fewer babies, and the incentives that they encounter to consume more or to consume less.

This is a really tough nut. If any of you think this is simple, just think of what's going on in the global financial crisis. The people of the world are trying to stimulate consumption. They're desperate not to be poor. And that flies right in the face of the environmental catastrophe. I don't think there's any easy answer on that. Yes Blake?

Student: People are interested in [inaudible].

Professor Stephan Stearns: Right, Bob Wyman teaches a class on population growth. By the way, let me just take one of Bob's slides, which he shared with me recently. If you go around the planet and you ask people how many babies do they want, good sociological research indicates that they want about two-thirds of what they actually get.

And that suggests that the easiest way to solve the population problem is not to do anything Draconian, but just to give every woman on the planet control of her own reproductive fate; by whatever means. Okay, I just wanted to make sure I got that message across up front.

Now today I'm going to discuss extinctions, and I am going to do it from ecological, economical, evolutionary and personal points of view. And within the ecological literature this is an old chestnut, and basically back oh say about thirty to fifty years ago there was intuition that suggested that the more diverse an ecosystem was the more stable it would be. And people like stability, they don't like to be hit by surprises, and so diversity would be good because it conferred stability.

Then Bob May showed that more diverse communities can be less stable. That's not a necessary logical connection, that more diverse things are more stable; sometimes more diverse communities are less stable.

Since then there have been a lot of experiments. There isn't a convincing clear pattern. More recent theory shows that sometimes diversity can increase stability. This one seems to be a moving target, and I think it's one where we have to be modest and say that, "You know, in any particular circumstance we don't really know what would happen."

Stability itself is a fairly abstract term, and it can either refer to resistance, which means ability to remain in the same state, or to resilience, which means ability to return to the same state following a perturbation; so bending without breaking. And that is probably more important in the real world. Okay?

Now, what do we actually know experimentally about what species diversity does to ecosystems? Well there's some evidence, by the way, that most of this data has to do with plants, or plants and insects. A richer community appears better able to survive a drought. That is probably because the plants in interaction with each other are actually conserving water locally.

If you look at net primary productivity, as you increase the number of plant species, the productivity, in terms of kilograms of carbon fixed per square meter per year goes up and then levels off; so there's diminishing returns. But the more different kinds of things, at least at the beginning, that you pack into a given space, because they're partitioning the environment differently the more they're going to be able to take out of the sunlight and the C02 and the water that's in the system, and convert it into biologically useful materials.

There's some evidence that as you increase the number of species in the community, the harder it is for an invasive species to get into that community. So these kinds of things are done usually in fairly simple experimental gardens. And I think that the application of that to the real world I have to remain agnostic on; it might work, it might not.

Recently there was a very nice paper--this in the Proceedings of the Royal Society this year--showing that more diverse pollinator communities provide more reliable service. So this X axis here is proportion of native vegetation, and this is the number of pollinator individuals, and this is again proportion of native vegetation and number of visits.

And basically what it's showing is that the more diverse the pollinator community, the more likely it is that the plants in it are going to get pollinated, because the different kinds of pollinators are complementary, they're trading services as they come in.

And this connects a bit to ecosystem function, because after all one of the things that Mother Nature gives us in agriculture is the services of the pollinators. And if we didn't have them, the almond industry and the apple industry of the world would collapse. So if we do things that wipe out the pollinator community, or radically simplify it, this paper suggests we can expect that we're going to have a decrease in our fruit and our nut crops.

So a few ecological points about diversity is that it does seem to improve some ecosystem properties. There's some evidence that connects species diversity to resilience and to resistance to invasion. Not too many people who have been working in the ecosystem function end of science have been terribly worried about the diversity of individuals in genes; they've been looking mostly at species diversity.

But it may very well be that if you have say a group of pollinators and you look within a single species and you compare very genetically diverse species of pollinators with very genetically homogenous species of pollinators that the genetic diversity may also have a significant impact. So there are a whole series of levels at which one can ask the diversity question, and not all of them are equally well researched.

Now let me just go back to the ecological view of diversity here and make a general comment on it. One of the arguments that conservation advocates use is that biodiversity is important for ecosystem function. And I'm now about to go into an argument on ecosystem function. Okay? And it's about how much it's going to cost us to replace those services.

And I'm just setting a pointer here, because I'll come back in a few minutes and point out that if you claim that you need a lot of biodiversity to maintain clean air, clean water, pollination services, everything that Nature gives us for free, but if Nature is really redundant, so that you could actually get rid of 90% of the species on the earth before you even noticed any decrease in ecosystem function, that you are then involving yourself in a political argument which is quite dangerous; and that is that you appear not to know what you're talking about.

Because your critics could come back year after year saying, "Oh, we've lost another 10% of the species on the planet and the ecosystems are still functioning just fine. You're just crying wolf." Until, of course, you get down to the point where you've trimmed away so many that the next ones really do make a difference to ecosystem function, and then we're all in deep water.

So there is a real problem here of being able to communicate to the general public, and the politicians, the issue that you could have a lot of ecosystem redundancy, which is buffering you from the extinctions that might otherwise be affecting ecosystem function, but at some point, if you've eliminated a lot of species, you will hit a limit at which there's no redundancy left, and at that point ecosystems start to collapse.

So let's now go through the economic argument, and you'll see how much it might cost to replace things. So there have been attempts, mainly by Bob Costanza and his group--he's now at the University of Vermont--to estimate what is the value of ecosystem function. And before we get into Costanza's, we can look at something like Habitat II.

So Ed Bass decides twenty years ago or so to build a very futuristic architectural piece out in the Arizona desert, which is an attempt to see whether or not you could actually build an interstellar spacecraft with a self-enclosed, completely recycling ecosystem, such that people could go in it and there would be everything in it that people would need to live forever. So if you just make one of those things and put it out into space, potentially humans could colonize other galaxies. It's a very bold idea, right?

So it costs 9 million per person, and if we wanted to replace the earth with that, you could figure that it's about 54 thousand-trillion to replace- to support everybody on earth, to get them to another galaxy. Unfortunately Habitat II didn't work. [Laughs] So it wasn't complete, and the people who went in it and tried to live in it had to bail out after about six months.

So this line of reasoning, which by the way is always going to end up with very big numbers, is basically a comment on externalization; and externalization is economics talk for things which are not my problem, thank you. So they are basically what we define, in our approach to the problem, as being outside the scope of the problem and outside the scope of our ability to come up with a solution. And I think you'll see that some of these things need to be internalized.

So the issue of externalization is that in economics it means it's not captured by the market. So it's not something whose consequences, whose costs, are reckoned into market calculations. So what Costanza and his crew did was they tried to calculate the marginal value of ecosystem services, and they just took the present value of the service and then asked, "If we just tweak it a little bit, how much is it going to cost us to replace--just looking at the current situation, if we try to calculate the replacement cost by tweaking that service so that Mother Nature doesn't provide it, we have to replace it, how much is it going to cost us?"

Well they have a lot of numbers in their paper, and I'll just run through some of them. This is not--I don't really expect you to memorize which ecosystem service costs more to replace. But I think it is notable that fertilizer in nutrient cycling, keeping all of the plants on the planet well fed, is something that Mother Nature does for us that would cost 17 trillion to replace.

It's interesting; I heard Ed Wilson in Washington a couple of weeks ago, and he was talking about figures like this, and he said, "You know, before this recovery plan, the stimulus package, I used to think that trillion was a big number." [Laughs] "And now it's a trillion here, a trillion there; after awhile you're talking real money."

You can see the kinds of things that people identify as ecosystem services, and certainly among them nutrient cycling, waste management, water supply, food, the regulation of the atmosphere, the regulation of water on the landscape, flooding and things like that, those are all quite serious things, and Mother Nature is doing a lot of that for us, and she's never- she hasn't been billing us for it lately.

And if you look at where this is going on, you'll find that the oceans are actually doing about twice as much as the land, and the estuaries are providing a tremendous amount of ecosystem services, and boy do people like to build their houses on the water. [Laughs] So if you just look at what happened to the coast of the Mediterranean or the coast of Southeast Asia or the coast of the Eastern Seaboard or Southern California, that is where people concentrate their living. They concentrate their living right around estuaries; Chesapeake Bay, for example.

And if you look at what are the important parts of the continental land masses, the wetlands and the forests are extremely important parts; although you can't really say that the grasslands are unimportant, they're still providing about a trillion a year in ecosystem services.

So the marginal value, back in 1997, the marginal value of total planetary ecosystem services was about 33 trillion. That was about four times the U.S. GDP at that time. Of course the U.S. GDP is greater now, but I'll bet you that the replacement costs for what Nature gives us for free are bigger now too. So it's a big number.

And that's an estimate of how much the global economy is essentially externalizing the costs of environmental impact, and environmental services. It's an estimate of the global magnitude of the tragedy of the commons, which is that we all individually want to take and use services, but our individual behavior is eroding the environment for the community. And that is an estimate of to what degree we're not connected to the consequences of our own actions, and to what degree we're not cleaning up our own messes.

So this economic view has been criticized; it's been criticized for bad economics and it's been criticized for bad ecology. I actually think that it retains an important take-home message, which is robust, which is after you apply all the criticisms and make all the adjustments, Mother Nature is still providing us with goods and services of enormous value, which would be impossible for us to replace if we had to. I don't think there's any getting around that. One can argue about the numbers, but I think the take-home message remains solid.

Now to come back to my earlier point about redundancy. We could probably get by with a lot fewer species. And this was brought home to me by my friend Pierre Henri Gouyon, who grew up in Central Paris, in the cinquième arrondissement, in the middle of a fairly artificial environment.

And basically he said, "Listen, we don't need ten million species on the planet. We only need 117. We need cows, sheep and goats. We need bacteria and fungi for cheese, wine and beer. And, in other words, we only need the things that will directly keep humans alive. And if we need some to provide these ecosystem services that we've just gone through, fine, maybe we need a few more, but we don't need 10 million."

Now Pierre Henri actually is a convinced environmentalist, and he actually got fired from his job for arguing with the French government about environmental problems. He had a radio show in Paris, and so he has been relegated to the Natural History Museum in Paris, which is a repository of biodiversity.

But this is--he made this argument in order to drive home the point that there's a lot of loose thinking that goes on about ecosystem function and redundancy, and maybe it's good to have a starting point from which you can argue upwards. Because once you decide that you're going to base your arguments for preserving species on practical grounds, and you're going to use economic terms to argue for them, then you have to back it up with data, and you have to back it up with well established facts. And by starting with just 117, I think that you are forced to confront a number of pretty serious issues in trying to make those arguments. So that's the economic view.

What would an evolutionary biologist say? Well basically it's pretty clear that every tip on the Tree of Life has been on the planet for 3.5 billion years, and they've all managed to make it this far. Good job. It doesn't mean one's better than the other, they've all made it.

And if we just think about relationship, we have shared ancestors with- we do share ancestors with all life on the planet, with the possible exception of those nasty viruses that have been so much with us this winter, and which are causing coughing in the audience. And you can go back and you can find relationships with virtually everything on the planet; just deeper and deeper in time.

And if you think about it, and you go back on the Tree of Life, there you are, maybe 3 billion years ago, and the archaea are going off in this direction and the eukaryota are going off in that direction; or you go back 15 million years and the Old World monkeys are going this way, and the hominidae are going that way. Or you go back 7 million years and the chimpanzees go that way and homo goes off in this other direction.

Basically if you're looking it as an evolutionary biologist, okay, some chunk of DNA went one way and some chunk of DNA went the other, down this branch, and they both managed to make it to this point, but you can't really derive any kind of morality about who has the right to dominate and who has the right to take over the resources of the world from that. It's just a neutral pattern, it's out there. Okay?

So from that point of view, looking at human culture is kind of interesting, because it's pretty late in the game of evolution that humans come up with this idea of dominating. And we are the winners. Okay? Actually this is quote from my younger son: Winners write history, losers write novels. The losers, who are the other species on the planet, pretty much have to accommodate to the winners, who are us, and who are dominating the planet.

And if you think about what we've done to them: if you think about say 25% of the birds going extinct in the Pacific; if you think about the fact that current levels of extinction during the anthropogenic extinction crisis are running at about 100 to 1000 times background rate; if you think about the fact that the total impact of human civilization on the planet is getting up to the point where it's approaching that of a big meteorite hitting the Yucatan, then I think that it's probably justified to use a phrase like the greatest crimes.

Okay, this isn't Zhuang Zi, whom I really like. But basically what we've done is we've driven to extinction, and are driving to extinction, many of the other occupants of the planet. And because it is increasing our quality of life, and our gross domestic products, and our gross planetary product, it gets spun as being necessary for standard of living and economic growth. So that would be an evolutionary point of view. Or let's say an evolutionary biologist who loved plants and animals would probably take that rather cynical look at the whole impact of human culture and history on the planet.

Now to be fair to us--you know, that's a fairly hard look at us--but to be fair to us, I think if any other species evolved to be dominant, it probably would behave pretty much the same way, because it would have gotten into that position by having a motivational structure that made it competitive and caused it to be very efficient at extracting and using resources.

And if we can ever actually behave nicely to other species, then I think that that would be a profound victory of culture over biology. If you want to use a kin selection argument, don't hold your breath on this one, because we haven't yet demonstrated that we can behave nicely to other human beings; and they're much more closely related to us than other species.

So I hope by this point you're realizing that the extinction crisis, and the meaning of biodiversity on the planet, is an interesting probe into our own nature and our own priorities. And in struggling with it there will be many points at which one could become pessimistic or cynical, but in fact I think you can look at it as an opportunity to learn an awful lot about ourselves and about the Nature that we interact with. So it's not all pessimistic. It's simply a very deep-cutting, revealing situation.

Now the personal point of view, it was captured in this book that my wife and I wrote, and I'd like to tell you a little bit about why we wrote it and the sort of lessons that we've learned from it. So that's the name of the book, and this picture is in it. These are two Swiss hunters in Southern Switzerland, and this is the last bear that was ever found in Switzerland. They shot it in 1905.

And this kind of thing, by the way, is now going on again in Idaho and Montana. The Department of the Interior has just lifted the ban on killing wolves. There are about 800 wolves in Idaho and Montana, and they're getting shot at again. So this sort of thing is the way people behave. These guys were very proud of the fact that they'd gotten a bear.

So why did we write the book? Well when I was--back in 1987, I was asked by the Swiss Government to comment on a whitepaper that had been written by an office in Washington, which had been set up by Congress to survey developments in science, and make recommendations to Congress on whether or not things were serious and needed action.

And Peter Raven and Ed Wilson had managed to move the biodiversity crisis up to a fairly high level, and this office had taken attention of it and had written a whitepaper, and the Swiss Government asked me and my group to evaluate this whitepaper. As a result of that, at the time that the European Union decided to do something about it, I was invited as Switzerland's representative, to come to this meeting, which John Lawton had arranged.

And it was held in England, and at the meeting I was asked to write a cover letter to our report, which was going to go to the European Commission. Okay? And I'm going to read a few sections out of that, because this is actually what got me to write the book.

So, "The causes of biodiversity crisis aren't in Nature, they're in human economic and reproductive behaviors." So it's right there. "And biological research isn't going to change human behavior. Human behavior can only be changed by education, economic, demographic policy, and by shared values that determine policy." Okay? At least shared values in a democracy; we were in European democracies.

"The long-term solution requires a reduction in birthrates and radical changes in consumption. However, starving, insecure and repressed people kill each other, they destroy the environment, they drive species to extinction." We certainly saw that in the wars in the Congo where the poachers were going through the gorilla reserves and chopping them up for bush meat.

"So the political challenge is to figure out a way to make people comfortable, secure and free. And that is a necessary precondition for long-term biodiversity stability." We can't wait to do that. Okay? We can't wait for political and economic change before we begin to protect ecosystems and save species. Because if we do, there's not going to be much left to save. So we have to start enforcing for the protection of Nature now.

And then the punch line was this; and this was in a conference of scientists. Okay? "Scientists often claim they need more money for research, and they'll accept it if you make it available. Politicians can avoid unpleasant decisions by saying that more research is needed." So there's kind of a nice way that they can help each other out here.

And, "The research must not be used as an excuse for not taking action. Because we already know this: there are too many people. Some of them, mostly in the developed world, consume too much, and both conditions must change." So I was just simply trying to state that, simply and straightforwardly. The reactions were really kind of interesting, and they also tell you something about the history of Europe. So Norway, Germany, Switzerland and England were for it, and France, Italy, Portugal and Greece were against it.

The French delegate felt it would play into the hands of the far right; it would provide a justification for deportation of immigrants; characterized my attitude as eco-Nazi; and, as usual, whenever the French are pushed into a corner and they want to pull out a trump card, a violation of the rights of man. Okay? Which they wrote. By the way, this French delegate went on to become the environmental head of UNESCO. So that was his attitude.

And the Norwegians, who are a remarkably self-satisfied and luxurious people, felt that it didn't go far enough. Okay? So they wanted to see something that was more revolutionary. The Germans thought it was a good statement. The British felt it was okay. The Dutch liked it. So I came away from that kind of shocked, but also realizing that humanity is having great difficulty agreeing on its value system, with regards to biodiversity. And if we disagree, we can't make much progress. Okay?

There's a lot of human value systems. Some people think extinctions are bad; just about anybody in this department would, because they love animals and plants, and that's why they have chosen this career. Some people might say that extinctions aren't important, that really what we need to do is have a healthy economy and save all the poor people in the world, and provide health care for that, and forget about Nature; you know, that's a secondary priority. And other people might say that extinctions might even be good.

You might wonder who that is. Any person who owns private property, on which an endangered species has been discovered, is motivated by the current incentive structure of U.S. Law to make sure that that species goes extinct before the Federal Government finds out that it exists.

Because if the Federal Government finds out that it exists, their property is open to condemnation proceedings, and they lose it. So I have friends who are ranchers in Hawaii who think exactly that way.

So, because of this, there are lots of conflicts; we can't reach agreement and we don't agree in that. So how do you change value systems? How do you get people to agree? How do you shift balance? And I thought at that point that it might be good just to show how people emotionally react to the process of watching a species go extinct. And Bev and I got together.

And I had originally tried to do this as a novel, and I discovered that my ability to write convincing fiction had been totally destroyed by twenty-five years of writing scientific papers. And so Bev, who's a journalist, said, "Why don't we go and interview people?" She's a journalist and she knows how to interview people. And she's a remarkably sympathetic personality. I'm kind of, you know, big and have a white beard and whatnot, but she's very sympathetic, and boy can she get information out of people.

And so we decided to try that. And our first interviews were with Christophe and Hedwig Boesch about the chimpanzees in the Ivory Coast that are going extinct, and they were very deeply moving interviews. We decided it was going to work. So we wrote the book. And I just want to take a couple of examples out of the book.

This is the 'Alala, the Hawaiian crow. And it was on the island of Hawaii; when I was young, you could occasionally see a juvenile flying in the northern part of the island. By the time we started looking into it, in the 1990s, there were only eleven crows left; they were down from 110 in the wild. And they had disappeared from every ranch, except the one ranch whose owner kept the biologists off the ranch.

And basically what had been going on is that the crows--this is a skull of an 'Alala--the crows had been encountering incompetent people. And the take-home from that particular chapter is that competent people are in short supply.

So in order to try to save them, the biologists had taken more than a hundred eggs and fledglings into captivity, and they'd killed all of them; not one survived. And the owner of the ranch, where they were still managing to live, Cynthia Salley, she decided that she wasn't going to let anybody on the ranch who was not really motivated to help save the crow, and so she told the biologists that if they were going to work on her ranch, they couldn't publish any of the results; and that immediately stopped all activity. [Laughs] So the biologists were interested in their publications as much as, or perhaps a little more than, they were interested in the crows.

And what happened--oh there was a crazy incident. U.S. Fish & Game told Cynthia that she was in violation of the Endangered Species Act, and so in order to save the crow--remember, they'd already killed a hundred--they were going to come in with a helicopter and net the remaining crows out of the air. Now they admitted that they hadn't practiced on house sparrows. Okay? And there are only eleven of this species left in the world. So the helicopters are going to come in, and a biologist, hanging off the helicopter, is going to net the crow out of the air, because Cynthia wouldn't allow them onto her property.

Well at that point Cynthia realized how crazy it was, and went to the governor and got the governor to intervene. And a committee from the National Academy of Sciences came out, got the Peregrine Foundation involved from Idaho, and some competent people reassured Cynthia that they would be able to deal with the situation. So they took some of the remaining crows into captivity and established a captive breeding program that now worked.

And in 1999, in September, Bev and I went up, and we saw the aviary where the baby crows were living. And the last two--it was a pair, a male and a female--the last two wild crows were outside; they were sitting up in a tree, looking at the baby crows in the aviary. Baby crows were making lots of noise, as baby crows will, and the adults had been drawn to the noise.

Now it turns out that if you are a baby crow, and you don't have a wild reared parent, you don't have anybody to teach you that you're supposed to shut up by 7:00 in the morning. And so every time they released some of these captive reared crows, they talked a lot, and they got noticed, and they got eaten by the rare and endangered Hawaiian hawk. [Laughs]

So there still are some captive reared crows, but they can't release them. And so essentially this species now exists in captivity; it doesn't exist in the wild anymore, it's gone extinct in the wild.

The next story has to do with economic and demographic processes. And this is a story from Chinese history. It was assembled by a Dutch diplomat named van Gulik, who among other things wrote some nice mystery novels set in China, set in Tang China. And it's about white faced gibbons.

So the white faced gibbon currently exists in Southern Vietnam and in Thailand. At the beginning of written Chinese history, there were white faced gibbons north of Beijing. So it over-wintered in the mountains, in the snow, north of Beijing. By the time of the Tang, it had been--by the time the Tang fell, so say roughly 900 or 1000 A.D., had been pushed down to the Yangtze, and then since then it had been pushed out of the country.

And it was a very important symbol in poetry and painting. The gibbon and the crane were both symbols of longevity. When a Taoist saint got old, he was supposed to turn into a gibbon and become immortal. The male gibbons have a very haunting cry, and if you are a monk meditating in a monastery on say the banks of the Yangtze Gorge, you could hear, at 5:00 in the morning, a gibbon fifteen kilometers away, giving out its territorial cry, and for that it brought in all of the magic and mystery of Nature into their imagination. So it became an important cultural object.

Well, van Gulik made this map, which basically--so this the Huang Ho, the Yellow River; this is the Yangtze here. And it shows sightings of gibbons, all labeled at different times. And basically by the end of the nineteenth century they'd been completely pushed out of China.

Now the interesting thing about that is that in A.D. 170, in the later Han Dynasty, a group of policy wonks come to the emperor and say, "Oh Emperor, the gibbon is going extinct, and it's a terrible thing." And the emperor says, "Yes, it is a very important part of our culture, we must preserve it. I authorize the army to stop the peasants from cutting down the forests." That is what was causing the gibbon to go extinct; it was habitat destruction.

And the habitat destruction was driven by demography. Poor farmers were having babies, and they needed charcoal to cook food to feed their babies. So for a year or two the army went out and protected the forests. But then there was a revolution, the Han Dynasty fell, the central control vanished, and the demographic processes did not change. There were still poor farmers having babies, and they still needed to feed their babies, and they still wanted charcoal.

So basically the forests of China got cut down, and the gibbon went extinct in China. And that happened nearly 2000 years ago. You might want to ask yourself whether that might not still be going on. Let's take a look at a more recent case in a politically stable nation, our own. And this has to do with the Barton Springs Salamander. Barton Springs--how many people here know Barton Springs; Austin, Texas. Have you swum in Barton Springs?

Student: Yeah.

Professor Stephan Stearns: Yeah. Barton Springs--people in Austin love Barton Springs; nice steady temperature, middle of a hot summer, jump into the springs. It's nice and cool, clean water flowing out of the karst formation. It's one of the big quality of life issues in Austin. Okay?

Well there's a little salamander that lives in Barton Springs, and it was used, together with the SOS, or Save our Springs, Alliance, as a method of trying to preserve the springs, and the area around it, from development. And the argument was with Freeport-McMoRan, and the Texas Republican Party.

Freeport-McMoRan is based in Louisiana, and it's one of the world's largest mining companies. It's a pretty cutthroat enterprise. These people have employed the Indonesian Army to put down revolts in the western part- in West Irian Jaya, the western part of New Guinea, where they have big copper and gold mines. And they play hardball.

And they were behind a scheme to put a city roughly the size of San Francisco next to Austin, on the area out of which the water drains, to go into Barton Springs. And so the environmentalist argument was, "We need to save the springs; therefore we can't have the city, which is going to just completely destroy our quality of life." And inside the springs there are about twenty more endemic species; actually, they've now found another salamander in the springs as well.

However, the U.S. Endangered Species Act doesn't allow you to use a legal argument to preserve a species unless it's been named. And so David Hillis, in 1991 I think, named the salamander and described it officially in the scientific literature as Eurycea s-o-s-orum, for Save our Springs-orum. Right? And it's a cute little salamander. Here it is. It's about two inches long. And I've been in the springs and I've seen him.

And the political response to trying to get this species listed was really massive. So Kay Bailey-Hutchinson made sure there weren't any listings in the whole U.S. for a year, so that the salamander wouldn't be listed. And Mark Kirkpatrick and his then wife Barbara Mahler, and Bill Bunch, who's an environmental lawyer, they used the Endangered Species Act, and finally they forced the Secretary of Interior to list the salamander. It took four years, and during that four-year period there were no species listed in all of North America. This one little salamander was holding the whole thing up, for the whole continent.

So the development was blocked temporarily. By the way, if the development had gone through, it would have meant billions of dollars. It was big, big money. But this kind of conflict never ends. We've been back in touch with the people there recently. We're trying to update this story a bit. They do have a successful captive breeding program. They have been able to limit the development somewhat. But the pressure is just not going to go away. The only way that the salamander will ever survive in the long-term is if committed conservationists manage to stay active. Because the economic incentive to develop is always there; it's not going to go away either.

So to summarize these different points of view. If you just take the scientific point of view. There are some advantages in some experiments that show biodiversity is a good thing, but results are mixed, and if you just review all of the biodiversity stuff, on ecosystem function, you have to come away honestly and say, "Well, it's a mixed bag."

The economic view is that the services would be very costly to replace, but how they depend on diversity is not clear; so that's because we don't know the redundancy in the system and we don't know when we hit the critical point.

The evolutionary view is that all living things are related, but there isn't any natural value in diversity. The evolutionary or purely scientific point of view would be that there is no value in Nature; so, you know, whether the planet's dead or alive actually doesn't make any difference.

If we then place a human value on diversity, for cultural reasons, as we saw with the gibbons, or in our own culture--every one of you is probably sitting in this class because you had a nice experience with some kind of biodiversity at some point.

Well basically what that does is we are placing a human value on something, and we've won the battle, and now our value system, which is our own homo sapiens value system of one kind or another--and you've seen there are bunches of them--is being placed on the rest of the planet. So some people spend to exploit the planet; some people spend to conserve it.

So what is the origin and justification of values? This interesting case of the biodiversity crisis causes us to confront that rather deep and personal question. And when you encounter people who are actively engaged in the conservation movement and environmentalism, I think you actually have to ask, "Are the values that they're deploying really something that is general and that you can derive for all people at all times, or is it simply an expression of their personal taste?" I happen to love orchids and porpoises and so forth. Other people like to eat porpoises. [Laughter] We're both human beings.

So if you want to read further on this--actually the one that I really recommend that you read is this book by E.H. Carr, on international relations between the two World Wars. That's sort of a modern Machiavelli, or Thucydides, that shows you how the nations of the world actually behave when they are faced with decisions on deep matters; they behave in a very, very hardball way. Okay, next time we go into behavior.

[end of transcript]

Course Index

Course Description

In this course, Stephen C. Stearns gives 36 video lectures on Evolution, Ecology and Behavior. This course presents the principles of evolution, ecology, and behavior for students beginning their study of biology and of the environment. It discusses major ideas and results in a manner accessible to all Yale College undergraduates. Recent advances have energized these fields with results that have implications well beyond their boundaries: ideas, mechanisms, and processes that should form part of the toolkit of all biologists and educated citizens.

Course Structure:

This Yale College course, taught on campus three times per week for 50 minutes, was recorded for Open Yale Courses in Spring 2009.


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