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Pleistocene Park




A group of scientists plans to bring bison, oxen and tigers to a controlled environment in the Far East to attempt to recreate the mammoth steppe that existed there tens of thousands of years ago.


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CHERSKY, FAR EAST - Like a frog hopping from lily pad to lily pad, Sergei Zimov strides from one clump of marsh plants to the next, perching wobbly for a moment on each sedge knob rooted in the subterranean frozen layers of the earth. Occasionally he misjudges a cluster's firmness and his foot plunges into the marsh water, his leg disappearing up to the knee. Within minutes, however, Zimov has reached higher ground and the carpet of mosses, lichens, birch bushes and scattered larches characteristic of the mixed tundra-taiga landscape of the region above the Arctic Circle. It is this starkly beautiful, wild land permeated with the fragrance of alpine sage that Zimov wants to see torn up and populated.


Zimov is no Soviet-style planner intent on draining the marsh and putting up drab high rises: He's an ecologist and director of a lonely science outpost in Chersky, an area in the northeasternmost reaches of Russia. Zimov points to a tangle of birch and willows several dozen meters away, a mosquito settling on his dirty-blond mane. Two agents of his destruction are picking their way across a ridge. They are young male Yakutian horses, off-white and pepper-flecked like the color of snow near a Moscow highway. Zimov expects that dozens of these horses, along with moose, reindeer and a herd of bison imported from Canada, will rip up the moss that covers the tundra. Mosses thrive in areas that aren't disturbed by animals or erosion. But grasses do well in such a dynamic environment, and thus, Zimov hopes, the animals in a few years will have banished the current ecosystem from a 24-square-kilometer preserve, supplanting it with a grassland resembling that which existed here during the last ice age.


The idea is to reconstruct at least a small chunk of the mammoth steppe, a vibrant ecosystem teeming with mammoths, bison and other grazers that dominated much of Siberia before vanishing after the frigid Pleistocene Epoch ended 11,000 years ago. Humans arose during the Pleistocene, which spanned hundreds of thousands of years and saw North America and Europe scoured by the grinding advances and retreats of glaciers during one ice age after another. In creating what Zimov calls "Pleistocene Park," he and two U.S. ecologists - Terry and Mimi Chapin, a husband-and-wife team at the University of Alaska - are embarking on an ambitious experiment that aims to test theories about what forces shaped, maintained and ultimately vanquished a long-gone ecosystem.


The project may also save a vanishing breed. It marks the first attempt to restock Siberia with bison, a species that went extinct in this region at least 2,000 years ago. The researchers plan to import a plucky survivor from northern Canada, a rare subspecies called the wood bison. "If all the wood bison in Canada were to disappear," Zimov says, "we could give some back." The plan rates high on aesthetic grounds. "It makes sense to reintroduce species that have been recently extirpated by human hunting or habitat encroachment," says Paul Koch, a specialist on Pleistocene-era mammals at the University of California, Santa Cruz. "It's just planetary hygiene."


Koch and others point out that the project's main goal - restoring the mammoth steppe - could be doomed because of missing elements that are impossible to reproduce: the namesake mammoths, of course, and certain climatic features of the Pleistocene, such as cooler temperatures and less carbon dioxide in the air. "You still don't have analogs for climate," says Russell Graham, curator of vertebrate paleontology at the Denver Museum of Natural History. Still, experts say the experiment is important, and some are calling it a watershed in efforts to study lost ecosystems. "It's a very exciting idea," says Paul Martin, who studies Pleistocene extinctions at the University of Arizona.


Weather is at the crux of the debate over whether Pleistocene Park will succeed. Most experts argue that Siberia in the Pleistocene was much drier than it is in today's epoch, the Holocene, which includes all of recorded history. They point to Pleistocene sediments, which harbor pollen and other remnants of grasses that thrive in dry soil. These grasses, in turn, fed an array of large herbivores, including mammoths, steppe bison, horses, moose, reindeer and woolly rhinos. Most scientists believe that a sudden and severe climate shift at the end of the Pleistocene - a warmup of about 5 degrees Celsius in just 20 years - set in motion a vast and inexorable turnover in which marsh-loving mosses and sedge conquered the circumpolar regions. This warming altered weather patterns, they say, bringing more rain and snow to Siberia and allowing plants that thrive in wet conditions to overcome the drier grasslands. That shift is believed to have spelled doom for large herbivores. The low-nutrient mosses, coupled with a new actor on the scene - primitive human hunters - drove mammoths, steppe bison and woolly rhinos to extinction.


Although Zimov agrees with much of that scenario, he contends that one key point is flawed. Climate change probably did not alter the balance of power among plants, he says. Zimov, whose staff at the Northeast Scientific Station has spent two decades probing Pleistocene sediments, argues that this rich soil only appears drier than today's soil. The region did not get less precipitation during the Pleistocene than it does today, he argues. Rather, the grasses were much better than mosses at sucking water from the soil and releasing it into the air. Besides, he says, the Chersky region hardly gets a soaking these days: It receives less than 20 centimeters of precipitation a year.


Terry Chapin recalls being "intrigued" by Zimov's ideas when they first met at a conference in Oregon in 1991. But he was also "somewhat skeptical," he says, before looking at a computer model Zimov had developed to predict how steppe or moss ecosystems might have thrived under various ecological or climatic regimes. In a seminal paper in the November 1995 issue of The American Naturalist, Zimov, the Chapins and three colleagues argue that with higher precipitation levels factored into the equation, the Pleistocene climate could have supported today's mosses just as well as it did the mammoth steppe.


What instead drove the transition to an emptier, moss-covered landscape, they say, was the demise of the aggressively hunted big grazers. By churning up the ground with their hooves, bison and otherheavyweights could have prevented mosses from gaining more than a weak toehold on the landscape. The grazers' dung provided fertilizer for grasses that, in turn, nourished the animals. With the gradual disappearance of big herbivores, the ground was disturbed less and grew poorer in nutrients. Such conditions, the researchers argue, could have ushered in mosses and exacerbated the herbivores' decline. Zimov points out that mammoth-steppe grasses persist today in areas of Siberia rich in nutrients - along rivers and streams, for instance - or in areas where mosses were disturbed by buildings, roads and other human activities. "We don't have this ecosystem now for the simple reason that we don't have enough animals," he says.


Zimov hatched Pleistocene Park as a way to test his contrarian views - in particular, that a herd of bison, along with the other grazers, ought to inflict enough punishment on mosses to allow grasses to mount a comeback. Northern Siberia's climate is too harsh for North American plains bison or European bison. But a subspecies called wood bison (Bison bison athabascae) should survive in the park. Larger, darker and with a more pronounced hump than its southern cousins, the wood bison was presumed extinct until a small herd was discovered in northern Canada in 1959. Wood bison are thought to be the closest living relative to the extinct steppe bison.


Zimov and the Chapins intend to fly in 25 to 28 bison from Canada to Chersky and acclimatize them in a fenced-off section of Pleistocene Park. The bison would be mostly young cows and a few young bulls to ensure "the maximum rate of reproduction," Zimov says. Within a few years, the growing herd would range freely in an existing national reserve that encompasses the park. Then, several years from now, bison would be allowed to roam in the 500,000 square kilometers of lowlands between Siberia's Indigirka and Kolyma rivers, a remarkable transformation for a region haunted by the memory of Stalin-era prison camps.


Although endorsing the project, experts point out shortcomings that could undermine its success. "If this is really going to work, they may have to try something much more daring and ecologically risky," says the University of California's Koch. He predicts that bison and other grazers won't disturb the mosses enough. The mammoths and woolly rhinos, he says, were critical to maintaining the Pleistocene steppe by clearing snow, rooting up vegetation and knocking down bushes and small trees. With those species long extinct, Koch argues that it would make sense to introduce the closest living relatives - Asian elephants and white rhinos - if these more southerly species were able to adapt to the Siberian climate. "My guess is that most contemporary ecologists and conservation biologists would become apoplectic at the thought of releasing exotic living organisms of this size and ecological consequence," he says. While it may be too early to undertake such an effort given the insufficient state of knowledge about these species, Koch says, "if we don't act soon we may not get the chance."


Such a plan might also seem a fantasy in the grim realities of Russia's downward spiral. Daniil Berman, an entomologist at the Institute for Biological Problems of the North in Magadan, says with affection, "Sergei is crazy to build Pleistocene Park in our economic situation." But he and others marvel at how Zimov has prevailed so far despite the odds. Anticipating in the early 1990s the inflation that would make rubles essentially worthless, Zimov went on a spending spree, buying everything from wood for posts to a heavy duty tractor for clearing land for a fence. "Zimov has a brilliant speculative mind, and on the other hand he is a man of action," says Andrei Sher, a Pleistocene expert at the Severtsov Institute of Ecology and Evolution in Moscow.


Zimov also won important allies in the government of Sakha, the vast Siberian republic formerly called Yakutia. Aware that Sakha could neither rely on subsidies from Moscow nor revenue from extracting its abundant but costly nonrenewable resources - gold, diamonds, oil and natural gas - Sakha president Mikhail Nikolayev has, out of necessity, embraced wildlife stewardship. "In Yakutia, the density of animals is very small," says Zimov. "What will the Yakutian people eat?" The answer could be wood bison and other herbivores that, Zimov hopes, will someday thrive on a reconstructed steppe and could be hunted in a regulated manner. And while it may be difficult logistically for Russians - let alone foreigners - to get to Chersky, Zimov predicts that adventure tourists flocking to Pleistocene Park could boost the region's fortunes. "I hope the density of animals in 20 years will be the same as in the Serengeti," he says.


Last spring Zimov took the first steps toward populating the park, buying 32 wild Yakutian horses with funds from the Sakha government and bringing them about 1,000 kilometers east to Chersky. This breed can put on a thick layer of body fat during the summer and fall that gets them through winter. And he is just finishing building a fence around the marsh in which the bison will adjust to their new climate. Heeding the "Field of Dreams" mantra "if you build it, he will come," Zimov is now waiting for the main player, the bison, to show up. To cover the estimated $330,000 cost of readying, shipping and acclimatizing roughly 30 bison, Zimov and the Chapins have applied for a grant from the Turner Foundation, a nonprofit organization established by American TV magnate and bison lover Ted Turner. The researchers expect to hear by Christmas: If they get their wish, the bison could arrive as early as March 1999.


If the bison take to their new environment, Zimov has plans to reintroduce other animals that could make the ecosystem balanced and self-sustaining. For starters, he plans to bring in musk oxen, already restored to central Siberia's remote Taimyr Peninsula. And he would like to bolster the ranks of predators to help keep the herbivore populations healthy. Already the park is home to a wolf family, but Zimov also hopes to add big cats - such as the Siberian or the Amur tiger - that would act as surrogates for extinct Pleistocene lions. As Berman points out, "this is not Pleistocene Park. This is Holocene Park with many Pleistocene elements."


Zimov probably will never see mammoths cavorting in his imperfect facsimile of the steppe. But the ecosystem he does end up creating is likely to keep researchers busy for decades to come. "Scientists are tired of discussing the greenhouse effect," Zimov says. "Now, maybe it will be interesting for them to discuss ecosystem reconstruction." The University of Arizona's Martin already predicts the experiment "is going to have a revolutionary effect on how we think about designing nature."


Richard Stone is a deputy news editor of Science Magazine.
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