JIM LEHRER: Now: a conversation about climate change to cap this week's stories. "NewsHour" correspondent Paul Solman talks to a Nobel Prize winner about his perspective on the links between climate change and biodiversity.
DR. ERIC CHIVIAN, Center for Health and the Global Environment Director, Harvard Medical School: There are natural extinctions way before humans showed up. But it is clear that the extinction rate now is 100 to 1,000 and even more times what it was before.
PAUL SOLMAN: Medical doctor Eric Chivian who shared the 1985 Nobel Peace Prize for spotlighting the effects of a nuclear war on global health.
DR. ERIC CHIVIAN: So, this is unprecedented.
PAUL SOLMAN: He's now speaking out about the threat of climate change as director of Harvard Medical School's Center for Health and the Global Environment. Harvard's Museum of Natural History was the setting for his current warning, which has received considerable attention, that global warming presents a clear and present danger to biodiversity, the broad but ever-narrowing range of plants and animals on Earth. So, there is global warming. Let's say it is exacerbated by humans and it threatens biodiversity. But what's biodiversity ever done for me? I mean, why should I care if global warming wipes out a whole lot of species?
DR. ERIC CHIVIAN: Because species have evolved unique physiologies and biochemistries over millions of years that have an enormous amount to teach us about how our bodies work in health and in disease. Let me give you an example. Two species of what are called gastric-brooding frogs were discovered in northeastern Australia. The female swallow the fertilized eggs. The eggs hatch in her stomach, become tadpoles. And, when they reach a certain level of development, she vomits them out to continue their development into adulthood.
PAUL SOLMAN: A rather quirky version of the maternal instinct that raises a question for the curious. How did the kitty Kermits keep from being digested by mom's stomach acids?
DR. ERIC CHIVIAN: These tadpoles secreted substances that prevented their being digested. And, so, scientists were very interested in finding out what these substances were, because they may have provided treatments and maybe even prevention for peptic ulcer disease, which affects 25 million Americans.
PAUL SOLMAN: Just a few exhibits away, however, what fate soon befell these unfortunate amphibians.
DR. ERIC CHIVIAN: This is the Exploring Extinctions exhibit, the dodo extinct, the great auk extinct. And here is the gastric-brooding frog in that jar. The only frogs anywhere in the world that raise their young in their stomach are now extinct. And the compounds that these tadpoles made to keep themselves from being digested, what they were and how worked, that information is gone forever.
PAUL SOLMAN: And with it, perhaps, something a tad better than Prilosec, because of a very recent extinction attributed in part to climate change, which reminded me, given the setting, of a more famous threatened critter which happens to be another favorite example of Chivian's. So, I have been tacking kids and my grandkids to this place for decades, and so I happen to know the polar bear is right over here, right?
DR. ERIC CHIVIAN: Oh, fantastic.
PAUL SOLMAN: So, what's the deal with the polar bear?
DR. ERIC CHIVIAN: Well, polar bears have become the iconic symbol of what we are going to lose with climate change. But their medical value is almost never mentioned. Let me tell you about that. For five to seven months, they go into hibernation. If we were bed-ridden for five months, we would lose a third of our bone mass. They have substances in their blood that prevent them from losing bone, even though they are not moving around. If we understood what those substances were, which we don't, we might be able to treat and maybe even prevent osteoporosis, which kills 70,000 Americans every year, costs the U.S. economy $17 billion.
PAUL SOLMAN: Well, maybe, maybe not, but says Chivian, there's more.
DR. ERIC CHIVIAN: They also don't urinate for five to seven months or longer. If we don't urinate for a few days, we're dead. If we understood how they accomplish this miraculous feat, we might be able to treat end stage renal disease, kills 80,000 Americans a year.
PAUL SOLMAN: Again, though, an assumption. OK, then try this, says Chivian.
DR. ERIC CHIVIAN: Polar bears also become massively obese prior to hibernating, and yet they don't develop type 2 diabetes. Type 2 diabetes related to obesity in the United States is virtually epidemic now. Sixteen million Americans, 5 percent of the population, have it, kills a quarter-of-a-million people in this country every year. If we understood how polar bears became obese, but yet didn't become diabetic, we might be able to treat these people.
PAUL SOLMAN: But the skeptic in me says, you have polar bears in zoos. You study them there. We learn what are you talking about. We don't need them out in the wild.
DR. ERIC CHIVIAN: Yes, we do. We have to study polar bears in the wild. Polar bears don't go into hibernation in zoos. We have to study the physiology that allows them to not get osteoporosis, not become sick, even though they are not urinating, and not develop diabetes, even though they become obese.
PAUL SOLMAN: Besides, it turns out our record for keeping species alive in captivity isn't all that impressive. Even with the medical interest in the gastric-brooding frog, for instance, the captive population only survived for three years after becoming extinct in the wild. But it's not just a species here or there that Dr. Chivian can point to. Get a load of these guys, cone snails, coral reef dwellers being wiped out as their habitats succumb to rising ocean temperatures.
DR. ERIC CHIVIAN: Each of these cone snails makes harpoons that it fires at its prey. They coat these harpoons with a cocktail of poisons to paralyze their prey. And then they bring the paralyzed fish into their enlarged stomach to digest it. What's fascinating about these snails is that each one is thought to make 100 to 200 different poisons. There are as many as 500 to 700 species. And, so, there may be as many as 100,000, maybe even 140,000, different cone snail poisons.
PAUL SOLMAN: Now, you will have to pardon me for asking, but why should I want cone snail poison? This kills little creatures. And I assume, if there was enough of it, it would kill me, too.
DR. ERIC CHIVIAN: That's true. But if a toxin is so potent that it kills every animal that it is injected into, that means it's affecting a very fundamental aspect of the way cells function. So, we had better look in to how those toxins work, because they may be medicines for pain. They may be medicine for making our heartbeat stronger or stopping arrhythmias.
PAUL SOLMAN: In fact, several painkillers derived from cone snail poisons are currently in clinical trials. And one, Prialt, was approved for use by the FDA in 2004.
DR. ERIC CHIVIAN: It is the most effective painkiller since the discovery of the opiates in the early 1800s. It's 1,000 times more potent than morphine, but doesn't lead to tolerance. It's a huge breakthrough.
PAUL SOLMAN: And it may not be the only venom of value, says Chivian.
DR. ERIC CHIVIAN: Others are in clinical trials to protect cells in the brain from dying when they don't get enough circulation, like after a stroke or after a head injury or during open-heart surgery. And we haven't even begun to identify the thousands and tens of thousands of compounds that these cone snails make. Here we have some examples of conifers.
PAUL SOLMAN: Finally, says Chivian, there's the story of taxol. Though it comes from a free, the Pacific yew, threatened by logging, not climate change, it is an object lesson in the value of seemingly disposable species.
DR. ERIC CHIVIAN: This tree was routinely burned and discarded in old growth forests because it was small, irregularly shaped. It had no commercial value. But the National Cancer Institute and the U.S. Department of Agriculture did this massive screening of plants in the United States in the '60s to find medicines that would be useful in treating cancer. And in the bark of this runted, useless tree, they found a wonderful molecule called taxol, which, in early trials, was shown to be the most effective agent in treating ovarian cancer, one of the hardest cancers to treat.
PAUL SOLMAN: Taxol and its follow-ons are now standard treatments for cancer.
DR. ERIC CHIVIAN: So, here's a drug from a tree that we know that with deforestation we might lose. And how many other wonder drugs like taxol are there in the forest, both in the tropics and in tempered areas, that we may also be losing?
PAUL SOLMAN: And this is where Dr. Eric Chivian and colleagues have written "Sustaining Life," a book that in the end makes a selfishly human case for saving other species.
DR. ERIC CHIVIAN: Every organism has to fight infections, has to fight cancers, has to defend themselves by firing off toxins that paralyze other organisms. So, it is up to us to look at the clues that nature has provided for us. And, in those clues, we can find medicines to treat many, many human diseases. We have no choice but to preserve the living world, because our health and our lives depend on it.
PAUL SOLMAN: Spoken like the advocate Eric Chivian has long been and is now once again, trying to facilitate the ascent of man with the help of the age-old world around us, which has been experimenting with the molecules of life for a lot longer than we have.