One Last Stand
Sequestering tigers in nature reserves may doom them to a slow, genetic death. To save them, conservationists want to give them freedom to roam.
By by Lily Huang NEWSWEEK
Published Oct 25, 2008
From the magazine issue dated Nov 3, 2008
Alan Rabinowitz has spent nearly three decades in a pitched battle to save the world's few remaining havens for predator cats. He's turned the Coxcombe Basin in Belize into the world's first jaguar preserve, and built the largest nature reserve in Taiwan, the first national park in the Himalayas, and the world's largest tiger reserve in Burma. Nevertheless, he knows he is losing.
The problem, Rabinowitz and other leading biologists now know, is that the classic conservation strategy of preserving habitat is in fact no defense against extinction. Twenty years ago, the devastation of natural forest was a visible danger. What went unseen was the damage sustained on a larger field of battle: the gene pool. A reserve may be a refuge for wildlife, but it is also a genetic sink. When a population of large predators is confined to pristine island of wilderness over time, they fall to inbreeding, leaving the species with weaker young and fewer defenses in an environment increasingly distorted by climate change. This is the deepening lesson of wildlife conservation from the post-industrial age to the genomic age: you can't save animals without saving their homes, and you can't save species without saving their genes.
Now Rabinowitz, a long-time director at the Wildlife Conservation Society (WCS) in New York, is taking a new approach to cat conservation. Not only is he working to bring back the world's vanishing tiger populations, he is establishing passageways for those populations to mix and preserve genetic diversity. Two years ago, Rabinowitz partnered with philanthropist Tom Kaplan to form Panthera, a nonprofit firm devoted to cat conservation. Their first objective is constructing "genetic corridors," which will traverse wilderness and cultivated land alike to connect existing habitats and allow individual cats to seek new territory for prey and new populations for breeding. Think of these as a kind of underground railroad for tigers: the conductors are the cats themselves, and the endangered cargo they bear is their genes.
The task is urgent, especially for tigers. The world tiger population, estimated at 100,000 a century ago, now totals fewer than 5,000; if Rabinowitz does not identify potential corridors now, in a few years development may make planning impossible. "Twenty years from now you won't have a chance to do anything," he says. "Eventually, this forest won't exist."
The model debuted in Latin America—jaguar country—for which Rabinowitz first had the idea. Significant swaths of yet undisturbed habitat and a largely consistent political climate make Latin America relatively hospitable territory for negotiating corridors. Despite the loss of more than half of the jaguar's habitat and a poaching binge that spanned more than a century, populations have resurged and the cats are still on the move. Costa Rica led the adoption of genetic corridors last year, followed by Honduras; Panama signed corridors into law last month. Rabinowitz estimates that maintaining the corridors will give jaguars access to more than 80 percent of their historic range.
Asia, by contrast, is more peopled, more pressed to grow out of its extreme poverty, and more rigidly divided up by dissonant governments wary of their neighbors. To join eight individually willful South Asian countries by a thread of tigers will be Rabinowitz's greatest act of diplomacy. He'll need to convince governments and ordinary people that a tiger migrating across a rice plantation is only the return of a natural ecological process—and no obstruction to development.
Territory outside of official wildlife reserves belongs to what Rabinowitz calls "the human landscape," and this radical approach to saving dwindling genes is "landscape-level conservation." What sounds like a logical updating of an evolving field is in fact a rewriting of conservation's first principle: people and wildlife cannot share the same space. Where there are people, wildlife is at risk. With a combination of dogged field work and diplomatic persistence, Rabinowitz has tried as hard as anyone to make the old model work, carving out parks and reserves in countries that had no prior interest in environmental protection. "I grew up in the traditional sense of thinking that was the endpoint," he says. "You go out, set up a park, people are outside, animals are inside, and you're successful. Outside, people can do anything they want; inside, people can't do anything. For the big animals, that's not going to work for the future." The British paleontologist Richard Leakey put it more grimly earlier this year: in forcefully keeping the two worlds apart, he said, we have issued "the death certificate of far more species than we've ever realized."
Before Rabinowitz's breakthrough idea of genetic corridors, work on another kind of wildlife corridor had already begun. Nearly 20 years ago, WCS got behind the first biological corridor, connecting rainforest habitats in Mexico and Central America. The idea was to have uninterrupted rainforest from Mexico to the Panama Canal, the large tracts of existing forest joined by forest arteries. It was a beautiful vision—and so ambitious that, though signed into international treaty in 1997, it is still in the process of being carried out to this day.
Rabinowitz's genetic corridor is ambitious in a different way. He formed the idea in 2001, when another set of researchers burst onto an underground genetic railroad already up and running—and didn't realize what they'd found. With new technology for DNA processing, geneticists at the Laboratory of Genomic Diversity in Maryland learned that populations of jaguars from Mexico to Argentina did not constitute different subspecies, as previously thought. "The first thing I did," recalls Rabinowitz, "I ran over and just looked at maps of Central and South America and said, 'What have we been missing?' " The answer was that, in spite of the risks posed by development and poaching, jaguars were still moving through much of their historic range—swimming, at one point, across the Panama Canal—and mixing their genes. Each individual jaguar was a unique combination of genes from the same vast pool.
Unlike biological corridors, genetic corridors are not stretches of untouched habitat. They are compatible with agricultural development, even private ownership of land—but there's a limit to how much development a traveling tiger will tolerate. What people will tolerate is another question, but Rabinowitz believes that resistance to letting tigers or other large wildlife onto developed land is more a matter of intellectual hostility than practical concern. Tigers, like all predators whose livelihoods depend on stealth, prefer to go about unnoticed. Even in tiger habitat, says eminent field biologist George Schaller, "you can go for weeks without seeing a tiger. They don't want contact if they can help it." Rabinowitz's own backyard in New York's Hudson Valley is a thoroughfare for coyotes—a fact he only learned when he set out a camera trap and got a picture of one. The animals' natural discretion is also one reason that mountain lions have made a comeback in California's Hollywood Hills.
A tiger's home range spans up to 800 square kilometers, but a male of "dispersal age"—about two years—will travel up to 1,000 kilometers in search of fresh territory for prey and mates. Only two reserves in the world are currently large enough to accommodate dispersals on this scale—the Hukawng Valley in Burma and Thailand's Western Forest Complex—but neither have the tigers to match their capacity. India, on the other hand, holds more than half of the world's tigers in numerous isolated pockets. Genetic corridors can help populate the large reserves and make small ones more viable. According to statistical models, if just one male tiger per generation—about ten years—makes a successful crossing from one habitat to another—from India to Burma, for instance, or Laos to Vietnam—and adds his genes to a different mix, the entire species gets a new lifeline. (Simply moving tigers from one habitat is quicker, but it almost always backfires: unless you catch a male right at dispersal age, says Rabinowitz, the animal will not accept its new home and try to find its way back. In its confusion, it is also more prone to conflict with humans and livestock.)
Tigers have different names in different parts of the world. India's are the Royal Bengal; in Thailand, conservationists are fighting for the Indochinese. The Siberian tiger looms large in that frigid northeastern tundra, while the Chinese are convinced that the South China tiger is the most beautiful iteration of all. They differ along a spectrum of size, color, and thickness of coat—but with the exception of the Sumatran tiger, which is truly in a genetic class of its own, there is only one tiger species. George Amato, head of genomics research at the American Museum of Natural History, says, "If you walked from southern India to Korea, at no place would you say, 'That [kind of tiger] stopped and this one started.' " The idea behind genetic corridors is not to create artificial gene flows between isolated groups, he says, but to reconstruct "the natural evolutionary path of these animals."
Thirteen countries own a piece of the tiger's natural range. One Panthera corridor would connect several small reserves in the Western Ghats, along the coast of India. Another would run the entire length of the Indonesian island of Sumatra. Between Russia and China, the Siberian tiger has periodically shifted its haunts as populations were hunted or lost their prey. Now some tigers are moving to China again, and Rabinowitz hopes that the story of their return to native soil might overcome the Chinese government's general indifference to wildlife and help legitimize a corridor in the northeast.
By far the longest segment of the tiger genetic chain will be the Himalayan-Indomalaysian corridor: descending from the Nepalese mountains to the very toe of continental Asia, it picks through Bhutan, eastern India, Burma, Thailand, Laos, and Cambodia on its way to Malaysia. Rabinowitz knows he may have to settle for less, because countries in this region are particularly averse to any proposal that "smacks of open borders." His first supporter is the king of Bhutan, a well-liked monarch who Rabinowitz hopes will influence India and Burma.
Before he can present genetic corridors to lawmakers, though, Rabinowitz first has to know where they can go. What enabled him to so readily act on his epiphany about jaguars was a new technology springing up in all corners of conservation science: Geographic Information Systems (GIS), a technique for making intelligent maps. These maps allow Panthera's specialists to assess potential corridor terrain on multiple levels, from elevation to the density of vegetation to the proximity of human settlement and infrastructure. Combined with precise Global Positioning System satellite technology, GIS becomes a powerful tool for Panthera's detective work. Kathy Zeller and Sahil Nijhawan, the company's corridor sleuths, use a "least-cost" model to deduce pathways for jaguars: with an understanding of the animals' behavior, they measure the known obstacles to jaguar movement down to the specific types of vegetation that can help stow away a cat (corn and sugarcane fields make passable cover, vineyards are not so good). Then they dispatch teams for "groundtruthing"—checking their multi-tiered maps on the ground, interviewing local farmers and ranch hands and collecting evidence of the cats' activity. Ultimately, the proof of a successful corridor will be in the scat, showing the dispersal of an individual's DNA from one population to another. In Latin America, Rabinowitz has to find the corridors already in use, in order to protect them; in Asia, since tiger populations are by and large fragmented, he has to find plausible corridors to implement.
Jaguar corridors are easier to create than tiger corridors. The illegal, exceedingly profitable market for tiger parts continues to thrive, from unregulated Asian border towns to Bangkok to New York's Chinatown. Local villagers still hunt the tiger's prey, because unlike domesticated pork or chicken, wild pig and deer meat are free. Tigers aren't even trying to disperse, in part because they can't, and in part because they are so few, they don't need to. "Even if there's a corridor," says Rabinowitz, "you only move if you have to leave. The dispersing happens from really solid, stable populations. Unfortunately, almost none of the remaining tiger populations are close to carrying capacity." In Asia, that means Panthera has less ostensible tracks to follow in figuring out where the tigers' preferred corridors would be. What they have is scat, collected from different populations, from which they can piece together a historic DNA trail that shows where movement once took place. Genes are a record of how closely populations are related, and thus how recently groups were split. The very genes the operation is designed to save contain the key to uncovering the past corridors that Panthera needs to re-create.
The primary negotiations for tiger corridors will not hinge on whether people can live with wildlife but whether states can. Corridors aren't a hard line against development; they need protection under zoning laws to keep from being obstructed by a dam, or a highway, or a factory—but otherwise, they're usable lands. A country can have corridors if it has a land-use plan, keeping corridor zones closed to industry and major infrastructure but open to agriculture. The key to saving the big cats is not a willingness to sacrifice development but a capacity for smart management.
Tolerance is something you can teach, but for more immediate effect, you can buy it. About 150,000 people live in Burma's Hukawng Valley Tiger Reserve, which Rabinowitz created in 2004. In addition to farms there is a police station, a firehouse, a Buddhist temple, several Christian churches, and a prisoners' work camp. The residents know they live in a tiger reserve because, in exchange, they receive benefits: teachers and power generators for otherwise abandoned schools, health services and medical supplies, guards on patrol—all paid for by Panthera and WCS.
For once, conservation has a pragmatic edge. The hope, in all its poetic irony, is that the new data-rich, processor-driven science of conservation will master the environment, so we can restore the wild and let it be—even in our midst.