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Is The Planet Facing A Mass Extinction?
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Is The Planet Facing A Mass Extinction?


Is The Planet Facing A Mass Extinction?

Is The Planet Facing A Mass Extinction?
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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


Tony Barnosky, author, Heatstroke: Nature in an Age of Global Warming, professor, Department of Integrative Biology, University of California, Berkeley, Berkeley, Calif.

George Amato, director and affiliated professor, Sackler Institute of Comparative Genomics, American Museum of Natural History, New York, N.Y.

Barry Sinervo, professor, Department of Ecology & Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, Calif.

Vance Vredenburg, assistant professor, Department of Biology, San Francisco State University, research associate, Museum of Vertebrate Zoology and California Academy of Sciences, San Francisco, Calif.

Plants and animals must adapt or go extinct as the climate changes. Paul Raeburn and guests talk about new research on populations of frogs and lizards, and discuss ways that conservation strategies may have to change as habitats shift towards the poles or creep up mountain slopes.


This is SCIENCE FRIDAY from NPR. I'm Paul Raeburn, sitting in for Ira Flatow.

As we sit here on this pleasant Friday afternoon - I hope you are having a pleasant afternoon - something is happening out there. Plants and animals are disappearing at an alarming rate, or some of them very close to disappearing.

Researchers say that about one-third of the world's species are now threatened with extinction. Nearly half of all bird and amphibian populations are declining, wildlife habitats are being overrun, and the march of invasive species is increasing on all continents in all kinds of ecosystems.

Now, if you were having a pleasant afternoon when you tuned in, it probably sounds like we're doing our best to ruin it. These are some of the findings, these rather grim findings in the third edition of the U.N.'s Global Biodiversity Outlook, a report released earlier this week.

The saddest part, though, might not be all the data about dwindling species. It might be the data about us, homo sapiens. A decade ago, world leaders set 21 goals to meet by 2010 to protect the world's biological diversity, and here's how well we've done: None of the 21 goals, not even one, has been met on a global scale.

Humans are continuing their exploitation of the planet and other species, and it's contributing to what some scientists have called the sixth extinction, a mass extinction similar in size to the one that ended the reign of the dinosaurs.

If it is a mass extinction, how serious is that? How much are we really to blame? And how is climate change affecting the outlook for endangered species? If some animals have to move to cooler climates to escape global warming, does that mean we also have to move our wildlife refuges?

These are just a few of the things we'll be talking about this hour, as we try to determine whether the situation is really as grim as it sounds, as the picture I've painted.

If you'd like to talk about these things with us, give us a call. Our number is 1-800-989-8255. That's 1-800-989-TALK. If you're looking for more information about what we're talking about this hour, go to our website,, where you will find all kinds of links to the topic.

Now I'd like to introduce my guests. The first, Dr. George Amato, director and an affiliated professor at the Sackler Institute of Comparative Genomics at the American Museum of Natural History in New York City. He joins us in our studios here in New York. Welcome to SCIENCE FRIDAY, Dr. Amato.

Dr. GEORGE AMATO (American Museum of Natural History): Thank you very much, Paul. I'm happy to be here.

RAEBURN: And Tony Barnosky is the author of "Heatstroke: Nature in an Age of Global Warming." He's also professor in the Department of Integrative Biology at the University of California, Berkeley. He joins us from a studio there. Welcome to SCIENCE FRIDAY, Dr. Barnosky.

Dr. TONY BARNOSKY (University of California, Berkeley): Thanks, Paul. I'm glad to be here.

RAEBURN: Is integrative biology the opposite of derivative biology? Or what is that?

(Soundbite of laughter)

Dr. BARNOSKY: In integrative biology, we look at what happens from the genetic through the ecosystem level and how all those different levels of biological process interrelate.

RAEBURN: You integrate all the biology. I get it. I got it.

(Soundbite of laughter)

Dr. BARNOSKY: Well, that's what we try to do.

RAEBURN: That's what you try to do. So I wanted to ask you about - well, I'll start with Dr. Amato. I want to ask you about the U.N. report which, you know, I painted this fairly grim picture. I'm not sure what other kind of picture I could have painted. But what do you make of that? Is it accurate? Do we think it's on track? And what do we conclude from it?

Dr. AMATO: I agree with you, it's a very depressing report, this many years after those goals were set to see that we haven't met any of the goals, as you've mentioned. This is a very difficult problem that we're confronting, and it's a global problem, and I think that's one of the significant challenges. You know, how do we face a global problem? How do we organize ourselves when our political systems are not typically used to dealing with global problems?

We see this in dealing with climate change, but when we talk about the extinction crisis that we face across the globe, this is a different kind of challenge than we've faced before, and it is accurate to note that we are not coming anywhere close to meeting the goals that we had identified as important just a few years ago.

RAEBURN: Now, is that because we haven't put through the effort, we haven't had the political will, we don't have the money? What do we think is the reason?

Dr. AMATO: Well, of course there are many reasons for this, and this is not to say that there haven't been individual successes in different places and that we haven't achieved, again, some important successes with individual species and individual protected areas.

But the trend that we see is unambiguously headed in the wrong direction. We see increasing loss of habitat, erosion of soils. We see over-harvesting of species, whether it's in the seas like bluefin tuna or in meat, in tropical forests that are now for a commercial harvest instead of just sustainable hunting.

And so all of these things are continuing to be a problem. But again, a lot of it is the complexities of trying to coordinate efforts across political boundaries.

There are, again, some successes in this way. There are some trans-boundary parks. There are agreements between nations, sometimes to address specific threats. But this is something that is very difficult, and we're trying to balance that, of course, at the same time that the U.N. is focused on poverty alleviation and other equally important issues.

RAEBURN: Dr. Barnosky, do you feel the same way? Do you likewise think this is a fairly depressing report?

Dr. BARNOSKY: Well, it is a depressing report. We would like to - you know, I think that most people, if you just ask them, are not going to say I'd love to see biodiversity disappear. And I think part of the big problem is it's not on people's radar screens.

So I would agree 100 percent that the first step is getting it to a profile where people understand and realize why biodiversity is important, and secondly, working across nations and globally to make something positive happen out of what will be a very negative situation if we all continue just going our own way and doing business as usual.

RAEBURN: Are we seeing a mass extinction, or is that overstating the case?

Dr. BARNOSKY: It's - I dont think it's overstating the case. Here's what we know. We know that rates of extinction that we're seeing today, should they continue for a couple of centuries, would probably put us into a true mass extinction.

We know we're in a very serious crisis. What we don't know is exactly how that compares to the other five times in Earth history where we've seen huge crashes in biodiversity. But we can be pretty sure that we're on that trajectory and that it really is time to do something.

RAEBURN: All right, now, we can - what I'll do is I'll bring on another guest to take this down into a bit of a microcosm here. One of the challenges in all of this, I think, is trying to figure out how climate change affects a local species or a particular species in a particular area. Is the habitat for that species drying up? Is it becoming too warm or too cold or too acidic or whatever might be happening?

Global warming and climate change has particular effects, I think, in every different spot. So let's talk to Barry Sinervo, who's a professor in the Department of Ecology and Evolutionary Biology at the University of California, Santa Cruz. He joins us on the phone from France. Welcome to SCIENCE FRIDAY, Dr. Sinervo.

Dr. BARRY SINERVO (University of California, Santa Cruz): Greetings from France, Paul.

RAEBURN: Greetings from France. Thats a rather nice climate right there, wherever you are in France.

Dr. SINERVO: Well, it's kind of drizzly and dreary right now.

(Soundbite of laughter)

RAEBURN: Not such a nice - okay, good. I feel better then. So tell us a little bit about your new study on lizards in Mexico, what's happening with them and whether or not there might be some link to global warming.

Dr. SINERVO: Well, we started actually studying the lizards here in Europe, and then we moved over to Mexico, and we noted extinctions here in Europe occurring at an incredible rate in the last decade.

And the lizards here are actually cool-adapted, and so we thought there may be a link to climate warming, but this far north, you had to wonder. And so when we started work in Mexico, we saw exactly what we saw here in Europe, and the cool-adapted lizards at the tops of mountains were really getting affected the most.

And that, the pattern in Mexico was even more stark and clear, and the climate signature was really pretty obvious when you looked at both those places, but in particular in Mexico because we had about 200 sites that we surveyed. And so it really became...

RAEBURN: Where were these sites? Are these anyplace any of us would wander into on vacation, or are they off somewhere far away?

Dr. SINERVO: Some of them are actually pretty nice vacation spots, so in the Yucatan Peninsula and then all around Mexico City in what's known as this trans-vulcan area, where all these volcanoes are found, and then in Northern Mexico.

And so they're basically occurring all across Mexico and always at the low-elevation part of a species range and at the southern limit of the range. So that's kind of the clear signature of sort of climate or warming sort of forced effects.

RAEBURN: Okay. Now, you've determined that the population of the lizards has fallen.

Dr. SINERVO: Well, in these places it's actually collapsed completely. So these were based on surveys that my colleagues had done that are co-authors of the paper in the 1980s and '90s, and we went back to the same sites, and we found that now they were locally extinct at about 12 percent of the Mexican sites and about 30 percent of the European sites in the southern part of this lizard's range here in Europe.

RAEBURN: Now, what's going on?

Dr. SINERVO: So what happens is that climate warming has been kind of ramping up, and over the last three decades or so it's gone up by about two or three degrees C, and this is in maximum air temperatures at a very particular time of the year.

It's not averaged across the year. It's actually only in the spring, and so those two or three months in the spring where climate warming has hit these animals the hardest has actually pushed them into the red zone, and they're starting to collapse all over the world.

It's not just in Mexico and Europe, but we extended the observations with ground troops(ph) in South America, Africa - and Madagascar is a particularly devastating place right now. There's over 20 percent of the local population is going extinct, and then onto Australia. So it's kind of a five-continent-wide sort of pattern that we picked up on.

RAEBURN: So these are a lot of different species of lizards and a lot of different kinds of environments, but similar things happening.

Dr. SINERVO: Yeah, so it's absolutely parallel, in fact. Across the globe the model predicts these extinctions are really arising from the climate change effects, and it's hitting certain species harder than others because they're in places where they've evolved a cooler body temperature, and that makes them much more prone to extinctions.

RAEBURN: Now, you're talking about a rise in temperature, in Mexico anyway, of two or three degrees. That's - I mean, two or three degrees. You know, you take off your extra shirt if you're a lizard, I guess. So in other words, the point is it's not too much. Why is that slight increase having such an effect?

Dr. SINERVO: Yeah, so that's two or three degrees Celsius. So if we translate that to Fahrenheit, it's about five, and then if you - you imagine what happens in Mexico is that it's actually pretty warm right now in the Yucatan, you know, well over 30, so well over 85 and 90 there, and getting into 95, 100 at times.

And what happens is the lizards can be out, but they can only be out a fraction of the day now, and that pushes them into kind of a very difficult situation energetically.

RAEBURN: Let me stop you for just a moment because we're coming up to a break, and then you can explain that difficult situation to us. More on climate change, biodiversity, lizards and lots more. Stay with us.

(Soundbite of music)

RAEBURN: From NPR, this is SCIENCE FRIDAY. I'm Paul Raeburn. We're talking this hour about biodiversity and climate change with my guests: George Amato, director and affiliated professor at the Sackler Institute at the American Museum of Natural History here in New York City; Tony Barnosky, author of "Heatstroke: Nature in an Age of Global Warming, professor of biology at the University of California in Berkeley; and Barry Sinervo, professor in the Department of Ecology & Evolutionary Biology at the University of California, Santa Cruz.

So Barry Sinervo, you were explaining to us about the energetic situation with the lizards and why a rise of only two or three degrees can be such a problem for them.

Dr. SINERVO: Yes, so it's easiest to think of when you reference it to these extinct sites, where we now have registered local populations going extinct and where they're right on the verge of extinction.

So back in actually it's now three years ago, we put our little lizard models that register kind of the temperatures that lizards were register at these extinct sites.

RAEBURN: What's a lizard model?

Dr. SINERVO: So it's just a piece of PVC pipe, sealed off on both ends and painted gray. So it absorbs the sun's rays just as a lizard would, and then you hook it up to...

RAEBURN: So this is high-tech stuff. I could build this at a Home Depot here.

(Soundbite of laughter)

Dr. SINERVO: I did it down in the Yucatan at one of the local stores. You know, you just went in there and asked the guy for these pieces of plastic. And you hook it up to a little computer that registers the temperatures throughout the day.

Now, when we put these out at the extinct sites, what we found was that it was impossible for a lizard to be out for nine hours of the day, and the last time, it was possible to be out, say, for four hours in the day was back in 1998.

So now go to these sites that are now on the verge of extinction. They're right at that four-hour point where they're now restricted, during the spring breeding season, when females have their energetic needs the highest, by four hours a day. So that's almost a third of their day.

And at these extinct sites, they're well over that. They're up to about three-quarters of their day completely restricted. So that's what pushes them over the edge. They can't be out foraging.

RAEBURN: Can they I guess they can't evolve to change to this thing, but can they adapt, or can they do something? Do they have no strategy?

Dr. SINERVO: Well, that's what we addressed in the paper. We actually looked at the whole process of adaptation and the rapidity of climate change, and that's an incredibly interesting question and right to the heart of the matter.

What you find is that lizards, let's say, could evolve a higher body temperature, but but that takes time. And what we know about the genetics of body temperature is that it's not that heritable so that the low heritability of body temperature is what seems to constrain them.

And you think of adaptation as, you know, allowing an animal to adapt to a new optimum. But in this case, because the optimum has shifted so quickly, too many individuals have to die selective deaths to essentially evolve that new optimum that you basically end up in a population that's in negative decline for about 30 years. And at some point, it just snaps and goes extinct.

RAEBURN: Tony Barnosky at Berkeley, do you know of other examples of this kind of thing? Are there other local extinctions or near-extinctions like this that seem to be related to temperature change?

Dr. BARNOSKY: Yeah, I think there clearly are, and it's not just lizards. For example, there was a recent study in Yellowstone Park that was looking at amphibians, which documented a very similar sort of phenomenon, that is in the northern range of Yellowstone, three-quarter of the amphibian species experienced very significant population declines and in some cases local extinctions due to essentially warming and drying over the past couple of decades.

In Yosemite National Park, people here at University of California at Berkeley, in the Museum of Zoology here, have looked at how mammals have responded to climate change over the past 100 years, and they've seen similar sorts of effects, though not quite as dramatic, but the mammals are disappearing in places and shifting around where they live, just as one would expect given the kinds of climate changes that took place there, the sort of warming that took place.

So I think what Barry has so elegantly shown here is a mechanism behind a very broad-spread phenomenon that's affecting many different kinds of animals all over the world.

RAEBURN: So Barry Sinervo, it's going to be with other animals, it might be other aspects of their lifestyle, you might say, that cause the problem, there are likely to be other examples where this small temperature rise could affect other species, too.

Dr. SINERVO: Oh, absolutely. Tony has hit the nail on the head. Our paper only talks about the lizards because it's so easy to prove that with the lizards because, you know, there's a generation of physiological ecologists who gave me the tools to kind of go out and figure out this stuff.

But it's more difficult, say, with amphibians because there's two things going on. There are temperature effects but also sort of drought effects, and so that makes it double hard to figure out whether it's climate change or some other factors. But with the lizards, it's really simple.

Though, you know, we're seeing it happen with all the major vertebrate groups from, you know, the frogs or if you go to, say, Mesoamerica just south of Mexico, we're losing salamanders along elevational gradients. So it's just happening everywhere for all of the major vertebrate groups, and it's probably happening for others, it's just these are the ones that are big and easy to follow.

RAEBURN: Well, thanks so much for being with us, Barry Sinervo. Make sure you pick up a baguette before dinner tonight. Barry Sinervo is a professor in the Department of Ecology & Evolutionary Biology at the University of California, Santa Cruz. He has joined us on the phone from France. Thanks very much for being with us.

Dr. SINERVO: Thanks very much, Paul.

RAEBURN: Now, Dr. Amato, if as we I mentioned in the introduction, even in places like, you know, Yellowstone and Yosemite, we're losing species. Are we wasting our time with nature preserves? They're not they don't seem to be doing us much good.

Dr. AMATO: Well, we are losing species in different places. The fact of the matter is, it's somewhat unpredictable exactly what will happen with different species, though Barry's study was very elegant, again, in terms of what it demonstrated with the lizards.

I think what it forces us, though, to do is think in a much more complicated way about how to preserve biodiversity. We know that simply putting a fence around a protected area and leaving it alone and hoping everything will be okay is not going to be a successful strategy. We are going to have to take into consideration things like climate change and other elements, actually.

And so, things like creating reserves that go across a great altitudinal gradient, so creating reserves that go essentially from the mountaintop to the lowlands will be important, allowing some species to be able to move their range up and down to be able to adapt, to some degree, to those kinds of changes.

Creating corridors that actually link areas from north to south will become important so that we can create opportunities, again, for species to be able to deal with this. And also some intensive management, literally moving animals and plants between reserves are probably going to be something that we are going to need to do.

RAEBURN: Yeah, that anticipates my next question. Is it possible to do that? Are we going to discover that we can do that, and it helps some species, or again, is that going to be like, you know, saving four species and losing 4,000 or something?

Dr. AMATO: Well, we won't be able to individually intensively manage all species. I mean, that would just be an impossible task, though there are plenty of examples of individual sort of iconic species, like large carnivores. For instances, tigers are a good example of a species that will probably have to be intensively managed, genetically and demographically, if that particular apex predator is going to persist in its systems.

But more, it will be sort of systems biology. Tony talked about integrative biology, but it really is sort of bringing together all of these various elements to better inform us in terms of making management decisions, restoring certain areas that have degraded or been somehow damaged from human activities, again thinking more comprehensively, systems-based.

You know, do we have the microbial communities? Do we have the pollinators? Do we have sort of a full complement of species for all of the ecological processes? These are things that are going to have to be taken into consider if we're going to maintain elements of biodiversity into the future.

RAEBURN: Let's take a call now. We have a minute here. We have Alicia(ph) from Mountain View. Are you there, Alicia?

ALICIA (Caller): Yes, I'm here.

RAEBURN: I'm pronouncing your name correctly?


RAEBURN: Okay, so go ahead.

ALICIA: Okay, I worked in some public policy things, actually over 30 years ago, related to city design, and I actually I really admire (unintelligible) work on nature in the cities. And cities have heat islands.

But I was aware at that time that a lot of things that we're experiencing with, you know, now I mean, I was aware that there were predictions all the way back in the 1920s about human population and how we actually exceeded the carrying capacity of the Earth in the 1920s for our own population, and now we're well beyond that, and we have the whole population-doubling phenomenon.

So it's interesting to me that all of this stuff about extinction is seen as news, when the reality is that a lot of scientists have been predicting this for a long time. And we've really failed to start to put in place rational public policy that helps people be aware of our responsibility with our population, to try to control how many children we have. In the same way...

RAEBURN: All right. Let me jump in to a couple of those issues that you already raised. Tony Barnosky, is true that we've known about this for a long time and that we're more guilty than we seem?

Prof. BARNOSKY: Well, it is true that people have, over the pass few decades, put together population models that demonstrate that as the number of people on Earth increase, there are few resources available to other species, so you might expect that the number of other species will decrease. There's a couple of different ways to look at that. So here's sort of the big picture perspective. Earth has a fixed amount of resources. We can actually trace the trade-off in use of those resources between people and other big animals going back hundreds of thousands of years. And what we find is that when - about 10,000 years ago, when people populations began to increase very dramatically...

RAEBURN: Around the invention of agriculture around that time, right?

Dr. BARNOSKY: Correct. There was a major crash in the number of species, a lot of extinctions of species of similar body size. That opened up a lot of new ecological space that was then filled by people over the ensuing few thousand years. Now, interestingly, we got back up to that pre-crash biomass in terms of large animals. But then, when we hit the Industrial Revolution, we exponentially began to shoot past it and are still doing so. So what happened there is we began to mine fossil energy out of the ground, putting new ecological energy into the system, which allowed us to grow our populations. And as we did that, we actually didn't affect extinctions of other species too much. Now we've grown past that point to where we are beginning to cause more extinctions once again.

So I think that, you know, there are several issues in there but sort of the key one is we found a way to augment ecological energy which got us through a period and kept biodiversity stable. Now we've shot past that, and unless we think about how we manage nature and how we manage ourselves, I would say that we are heading into many more extinctions.

RAEBURN: All right. I hope that helps, Elisa. Thanks for calling. Okay. So George Amato, one of the things that we thought about as we were preparing for the show was the idea of farm animals. Now, some farm animals are a contributor to global warming, I guess maybe a significant contributor. What about the survival of agriculture and farm animals? Is that an issue that we should be concerned about?

Dr. AMATO: It's interesting. It's another related issue in terms of the loss of genetic diversity. I mean, when we talk about the loss of biodiversity, we're really talking about the loss of genetic diversity on the planet across species and across really phylogenetic and evolutionary history. But even on a very narrow scale, even the genetic diversity that's arisen over years in terms of strains of crops and breeds of animals, there was a lot of genetic diversity that sort have arose out of that for species that were adapted locally, adapted to different kinds of conditions.

As modern agriculture has expanded, we've moved to this sort of factory farms where we either plant a single type of a single crop or we're able to produced large numbers of essentially genetically similar or identical animals. And in many ways that's yet another threat in terms of loss of genetic diversity, in terms of a disease that could affect one of those species, or even a healthier environment where we would be growing crops and raising animals that are more better adapted to sort of an integrative agriculture landscape. And so that's another important issue we should be thinking about.

RAEBURN: Let me pause for just a moment to remind everybody - I'm Paul Raeburn and this is SCIENCE FRIDAY from NPR.

Okay. So I mean, we wouldnt expect then that - serious disruptions in industrial agriculture because of the sort of technology and flexibility involved?

Dr. AMATO: Well, I think it is of concern and this is something that there's a lot of discussion. And this is really an interesting topic in and of itself, you know, genetically modified crops, genetically modified foods, the loss of genetic diversity from rare breeds and rare strains, and I think a lot of attention needs to be paid to that. However, in many ways, you know, I think that when we look at that connection to biodiversity, it's really been a lot of sort of poor agricultural practices that have contributed significantly to the loss of biodiversity, and that's something we need to think about.

But it's also the ecological services that come from more natural or less human-dominated landscapes. Again, before I mention pollinators - and they're a really great example of an ecosystem service that we need to actually have functioning agriculture in most cases, and yet little attention has been paid to the impacts of pesticides or land use practices on pollinators and other species that provide these ecosystem services.

This is something that we're going to need to think about very carefully if we're going to have sustainable agriculture. And it's a case for conserving biodiversity beyond its beauty and its diversity but in terms of its necessity for us to be able to have healthy human populations.

RAEBURN: Right. That's the one thing I think we'll get to after our next break, is what is the effect on human populations beside lizards and frogs. In the meantime, let's take a quick question from Gary in Kalamazoo, if I can find the right button here. I think we got him. Gary, are you with us?

GARY (Caller): Hi. Yes, I am. Hi, Paul.


GARY: This is fascinating and a bit unnerving for me. I own quite a bit of land in southwest Michigan here that is home to a very large colony of eastern box turtles, another reptile that is well-known around here and probably in the east, southeast United States. And one of the things you realize as you study these over the years - I've been doing it for about 20 years - these animals live as long as a hundred years in the wild. They're just a turtle, and yet they know what to do. They can survive almost anything. In fact, they've been in almost exactly the same form that they're in today since before the dinosaurs. They've - 250 million years or if you - if you're not into evolution, before the dinosaurs. Just believe that.

(Soundbite of laughter)

GARY: But they survived what eliminated - what grew the dinosaurs and then eliminated the dinosaurs and they still function exactly and effectively the same way. To me, the most peculiar issue that I am trying to deal with, because I do own a lot of land and I'm trying to manage it...

RAEBURN: Let me stop you for just a minute.

GARY: Sure.

RAEBURN: Sorry to interrupt...


RAEBURN: ...we have a break coming up.

GARY: Yeah.

RAEBURN: We'll take our break. We'll look at frogs in the Sierras, what's happening there. Please stay with us.

(Soundbite of music)

RAEBURN: From NPR, this is SCIENCE FRIDAY. I'm Paul Raeburn.

We're talking this hour about extinction, climate change and conservation with my guests George Amato, director and professor at the American - director of the Sackler Institute of Genomics and professor at the American Museum of Natural History in New York City, and Tony Barnosky, author of "Heat Stroke: Nature in an Age of Global Warming."

So let me just see if I can sum up Gary's question for him. Box turtles, something very familiar, a sort of beloved species in some places, I don't know that those are endangered, but are we likely to see changes in the populations of those kinds of animals as well, George Amato?

Dr. AMATO: Yes. In fact, that's a very good example. Actually, our first caller brought something that's related to this to our attention and talked about thinking about conservation in an urban landscape or even a suburban landscape. And there are many lessons to be learned there that will - you know, because things are happening there even more quickly.

Box turtles are a really great example. Where I grew up in Connecticut, box turtles were common when I was a child. They do not exist in Connecticut anymore. Now, this was...

RAEBURN: Really? They're completely gone.

Dr. AMATO: They're really gone.

RAEBURN: I'm not going to pin down your age here, but what are we talking, 20 or 30 years they have disappeared?

Dr. AMATO: Well, yeah. I'm 53. But they've really disappeared. Now, the reason they've disappeared there is because the nature of how fast they reproduce and all of this. They've been harvested as pets. The way we - primarily, the way we divided our suburbs up has created so many roads and crossings that they're hit by cars. We've just created a landscape for which - even though we talked about them surviving hundreds of millions of years or similar kinds of organisms, they weren't able to survive the modern suburb.

And yet in these same suburbs we have huge increased populations of white-tailed deer and turkeys. We now have coyotes where they didn't exist when I was a kid. So you see very different impacts on different organisms as we - as things change. These are things that, again, we're going to need to take into consideration. If we're going to want organisms like turtles and some of these species that are heavily impacted by our activities, we're going to have to think about housing divisions that allow, you know, large areas of contiguous land, not just everybody living on a half acre and subdivided by roads. And these are the kinds of things that we're going to need to think about, so I think that was a very good question.

RAEBURN: Yeah. I mean, it's interesting because, of course, the flip side of this thing is all those suburbs that have wiped out the box turtles have created jobs for people and homes for people and all kinds of things, so of course nothing is easy.

Dr. AMATO: Well, I don't think anyone would suggest that they're incompatible. I mean, I think that when we think very - you know, one of the suggestions, in a sense, even in a suburban development and in many areas they've done this, is in a sense sort of cluster housing, where the houses are closer together and then there are more greenways, sort of, that are larger and sort of allow for that kind of space to take place. That's useful for recreation for people. So there's no reason that people can't have homes and that we can't modify the landscape in a way that's more amenable to keeping biodiversity here with us.

RAEBURN: All right. Let's continue our globe-trotting now. We've been in Mexico, in Michigan, in Connecticut, and I think I've forgotten one or two. We have another guest waiting in the wings. Dr. - I'm sorry - Vance Vredenburg is an assistant professor in the Department of Biology at San Francisco State University. He has been looking at frogs in the Sierra Nevada Mountains. Is that right, Dr. Vredenburg?

Dr. VANCE VREDENBURG (San Francisco State University): That's right.

RAEBURN: Welcome to SCIENCE FRIDAY. Tell us something about frogs in the mountains.

Dr. VREDENBURG: Thank you. Well, it's a pleasure to be here.

Yes, my colleagues and I have been working on frogs here in California, where we have some of the largest protected areas in the United States. Yosemite National Park, Sequoia, Kings Canyon National Parks and wilderness areas - huge areas with no roads we think of as these pristine areas. And over the last several decades we've watched as the once most common vertebrate in the high mountains, the yellow-legged frogs, have gone - have just plummeted towards extinction with over 90 percent decline.

RAEBURN: This isn't the notorious jumping frog of Mark Twain fame, is it, by any chance?

Dr. VREDENBURG: No, it's not. That was the also-threatened red-legged frog, lower elevation.

RAEBURN: Let me interrupt for just a moment to tell our listeners that Christopher Intagliata, who produced this segment, used to volunteer in the Brigg's Lab at UC Berkeley where you used to work, I think.

Dr. VREDENBURG: That's right.

RAEBURN: So now we've completely disclosed our connections here, and we can continue. So looking at the red-tailed frogs as the one you're looking at...

Dr. VREDENBURG: The yellow-legged frog.

RAEBURN: Im sorry, the yellow-legged frog. The red-legged frog is the Mark Twain frog. I'll get this. So the yellow-legged frog - tell us a little bit more about exactly what kind of study you did there.

Dr. VREDENBURG: Well, so my colleagues and I have been looking at how an emerging infectious disease has been sweeping through populations of these frogs. And this is a it's a disease that is referred to as a chytrid fungus. So it's a fungal pathogen...

RAEBURN: Chytrid.

Dr. VRENDENBURG: Chytrid, yes.

RAEBURN: Spell that for me because I...

Dr. VRENDENBURG: It's C-H-Y-T-R-I-D. Chytrid.

RAEBURN: I wouldn't have gotten that. Go ahead.

(Soundbite of laughter)

Dr. VRENDENBURG: Many people call it citrid(ph) and all these other strange things. But it's a Chytridiomycete fungi, which is an aquatic fungus. It's microscopic. It has a flagellated stage, it actually swims through the water -it's called the zoospore - that actually swims through the water and looks for a host.

In this case, the hosts are only amphibians. So it infects the skin of amphibians and has been causing massive die-offs of frogs, of - and salamanders, we think, around the world. In fact, this disease is the greatest threat to vertebrate biodiversity of any known disease with over 200 species seriously affected, and many of them believed to be extinct.

RAEBURN: You know, it's all...

Dr. VRENDENBURG: It's affecting populations and species in Central America, Australia and here in Western North America.

RAEBURN: These are all frog species though, you said.

Dr. VRENDENBURG: Frog and salamanders.

RAEBURN: Frog and salamanders. Okay. Are there other of this, what is it, chytrid? Is that the word?

Dr. VRENDENBURG: That's a good question. Yeah. They are chytridiomycete fungi. There a quite a few of them, but this is the only one that's pathogenic to vertebrates. And it was only discovered in 1998.

So this is, you know, yet another one of these emerging pathogens that's popped up around the world. And in this case, it's affecting amphibians. But one thing I try to always remind people is that 60 percent of emerging infectious diseases in humans are zoonotic, which means non-human source. And out of those, 72 percent are from wildlife. So, you know, we think it's very important for us to understand the underlying biology even in diseases in things like amphibians that maybe not every one has a direct connection to. But if we can understand the biology that leads to these massive declines and extinctions of populations, we think it's every important for us to understand that so we can make predictions about what might happen in humans.

RAEBURN: Now do we Are there any frogs that are tolerant or resistant to this, or is there any clue in any of the species about what might be done to try to fight it?

Dr. VRENDENBURG: Well, that's the - that's one of the interesting findings or our - we just published two back-to-back papers. One of them shows, in the same species, shows a massive decline of these frogs. So we showed as this -epidemic wave, we showed it moving across the landscape of frogs and basically wiping out every single population along its way.

But the second paper that we published with Cherie Briggs out of UC Berkeley -I'm sorry - out of UC Santa Barbara, showed that another population of the same species was able to survive with this fungus. So we think we've made a real breakthrough in sort of discovering a sort of lethal threshold for the disease on individual frogs. So it's not just whether they're infected or not, it's how infected are they? And we think - and we're looking at things, of course, differences in things like host immunity, and may be pathogen virulence that could explain some of those differences in survival.

RAEBURN: Now, is there a global warming connection to this or not, or we don't know yet?

Dr. VRENDENBURG: We still don't know. I mean, certainly global warning is stressing out all kinds of organisms around the world. And amphibians, many amphibians have very tight schedules in terms of what they can handle, in terms of the temperatures that they handle. And it wouldn't be surprising to find out that amphibians for example, their immune systems might be weakened by the effects of global climate change.

But there lots of factors, lots of ways that climate change could affect amphibians. And it's already been shown that drought cycles, massive drought cycles affect these guys, and of course heat shocks and those sorts of things could affect them as well.

RAEBURN: Okay. Well, thanks very much for giving us another close up view of things to fit into our larger global view of climate change. Thanks for being with us.

Dr. VREDENBURG: Thank you so much.

RAEBURN: My guest has been Vance Vredenburg, an assistant professor in the Department of Biology at San Francisco State University. He's also a research associate for the California Academy of Sciences in San Francisco and at the Museum of Vertebrate and Zoology in Berkeley.

Still with me are George Amado, professor at the American Museum of Natural History in New York, and Tony Barnosky, author of "heatstroke: Nature in an Age of Global Warming," professor at UC Berkeley

RAEBURN: Dr. Barnosky, have you seen - do you know of other examples of diseases like this that have struck populations that might be related to climate change?

Dr. BARNOSKY: The short answer to that is, no, I don't. I think that what's really amazing about the study that Vince just talked about is they were able to demonstrate how fast a disease can flash through a population and have such devastating consequences.

Now in terms of amphibians elsewhere in the world in fact, people have pointed to an interrelationship between climate change and where the chytrid fungus organism can live. So it turns out that in Central America, this pathogen likes fairly warm nights. And as nighttime temperatures have been getting warmer, higher and higher in the tropical mountains, it has shifted its range, or it's thought to have shifted its range into places where it formerly wasn't abundant and affected the frog populations there.

So I think, you know, that's another thing you need to keep in mind with these diseases, and actually any other species interactions, is it's not oftentimes the direct effect of climate change on a species, but it's the indirect effect that is caused by interactions as new species responding to a climate change perhaps move into an area.

RAEBURN: All right, we just have a couple of minutes left. George Amato, is there any way out of this mess?

Dr. AMATO: Well, I think for anyone who does conservation biology like myself has to be optimistic, at least part of the time or else this would be a very difficult endeavor to be involved in. I think the more that we learn - and we saw two very important studies today. While some of their findings are somewhat depressing, the important element is that we've gained important new insights that we can take into our conservation planning. We're getting a better understanding of the ecosystems, what their stresses - the stressors are in those systems. And that will then provide us with opportunities to think about how to ameliorate those changes.

I think that, as Tony mentioned early on, one of the very important things is that this has to be, you know, on our agenda. I mean, we're - we talk about all of the immediate crises, whether it's the banks failing or other kinds of things, and yet this is something that has to be on our agenda equally. And once it is, I think that we've learned so much, and we continue to learn so much that we really do have opportunities in terms of how we manage protected areas, how we farm, how we harvest foods, how we do planning activities, how we do resource extraction. We can do all of these things in ways that will, in a significant way, help retain elements of biodiversity.

Some of the elements, how much we can impact climate change and how quickly we can do that, it's difficult to say. I mean, we've started down a path, but that does not mean that we can't engage in a serious set of activities that can make a significant difference in retaining important elements of biodiversity.

RAEBURN: And let me take this opportunity to remind everybody I'm Paul Raeburn and this is SCIENCE FRIDAY from NPR. Tony Barnosky, are you also a professional optimist or a real genuine optimist? Do we have a way out of here?

Dr. BARNOSKY: So, you know what, I am pretty optimistic by nature. Otherwise, you can't study something like extinction. You have to see a way out. And...

RAEBURN: That's professional optimism. I don't know if that's real optimism.

Dr. BARNOSKY: So here's the real optimism...


Dr. BARNOSKY: If you think of what we've got on earth right now, there are 46 percent of earth's terrestrial landscape can still be viewed as wild places or wilderness or undisturbed in the sense that it has less than five people per square kilometer living there. It's got at least 70 percent native vegetation, and it's got that - those two conditions in tracks of land that are at least 10,000 kilometers squared. So that's a lot of good area that we have to protect. Twelve percent of that is in - already protected in - legislatively, in some form or fashion now, so that's the very half full story.

RAEBURN: We're just about out of time. Just wrap it up quickly for me, if you can.

Dr. BARNOSKY: Okay, the wrap-up is that there are things we can do to make sure we save that for the future.

RAEBURN: Okay. Good. So we'll end on a high note. We'll try to end on a high note. Thanks very much to both of you for being with us. My guests have been George Amato, director and affiliated professor at the Sackler Institute of Comparative Genomics at the American Museum of National History in New York City. Thanks for being here.

Dr. AMATO: My pleasure.

RAEBURN: And Tony Barnosky, author of "Heatstroke: Nature in an Age of Global Warming," also professor in the Department of Integrated Biology at the University of California, Berkeley. Thanks for being with us.

Dr. BARNOSKY: Yeah, thanks. It was fun.

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