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| ISBN-13: | 9781610917179 |
|---|---|
| Publisher: | Island Press |
| Publication date: | 10/04/2016 |
| Pages: | 216 |
| Product dimensions: | 5.90(w) x 8.90(h) x 1.00(d) |
About the Author
Read an Excerpt
Future Arctic
Field Notes from a World on the Edge
By Edward Struzik
ISLAND PRESS
Copyright © 2015 Edward StruzikAll rights reserved.
ISBN: 978-1-61091-717-9
CHAPTER 1
Eight-Foot-Long Beavers, Scimitar Cats, and Woolly Mammoths
What the Past Tells Us about the Future Arctic
At Ballast Brook, on the north end of Banks Island in the Canadian Arctic Archipelago, the trunk of a spruce tree emerges from the eroding permafrost. Although it looks as if this tree might have died only two or three years ago, it has been entombed in an icy grave of peat and gravel for the past three million to five million years. This tree is a remnant of a boreal forest that once covered this stark tundra landscape.
In the summer of 1967, geologist Len Hills was hiking along this plateau at Ballast Brook when he spotted a large, fossilized bone protruding from the surface not far from that tree. It was cold, wet, and snowing at the time. Hills picked up the specimen, put it in his bag, and carried on without really knowing what he had found that day. Being a palynologist, he was more interested in finding the spores and pollen from the ancient plants that once grew here than what might have walked on four legs.
Hills didn't give the discovery another thought until Dale Russell, a paleontologist with the Canadian Museum of Nature, telephoned him some ten years later and asked whether he had ever come across some Cretaceous-era bones during his explorations in the High Arctic.
Hills thought it an odd request. At the time, very few scientists seriously considered the possibility that Tyrannosaurus rex and other dinosaurs had ever ventured anywhere near the polar world. It had never occurred to him that one or more of the unidentified fossils he had picked up during his many research expeditions to the Arctic could be that of a "terrible lizard."
Back in his lab, Hills searched for, and found, the fossil he had picked up at Ballast Brook that day. He gave it a wash and then had a good laugh when he and his colleagues finally figured out what it was. The fossil was not that of a dinosaur; rather, it was the shinbone of a woolly mammoth, a giant elephant-like animal that once lived in the Arctic.
For some time, no one knew what to make of that specimen or another mammoth fossil that was found on Melville Island to the northeast. Paleontologists knew that these big, hairy, elephant-like animals had lived in the Arctic at one time, but no one thought that their range extended beyond the north coast of the Yukon and Alaska on to the Arctic islands.
In time, paleontologist Richard Harington, the man who dated the fossil bone, came up with an explanation that seemed to satisfy most everyone then. Harington, arguably the world's most respected Ice Age paleontologist, suggested that Banks Island and parts of southwestern Melville Island were once part of the northeastern limit of Beringia, a verdant mass of lowland that periodically connected Arctic Russia to Arctic North America when sea levels were much lower than they are today because most of Earth's water was locked up in glaciers.
Over a period of tens of thousands of years, Harington suggested, most of those woolly mammoths that migrated across this continent sized lowland would have slowly moved southeast into Canada until massive sheets of ice that periodically expanded northwestward from the Hudson Bay region stopped them. He thought that some of them, however, may have stayed behind or retreated north across the ice sheets that connected the mainland to Banks Island when sea levels were so low.
Even today, many scientists assume that much of Banks Island and other parts of the western Arctic Archipelago were largely ice-free through the last period of glaciation and at least partially ice-free for hundreds of thousands of years before that. You can almost see it in the soft, verdant look of this treeless tundra on a warmish summer day. In places such as the Thomsen River valley, the sedge- and grass-covered terrain looks as if it had never been scoured by the sharp edges and heavy weight of ice that expanded to its Ice Age maximum 18,000 years ago before petering out 7,000 years later.
For most of his forty-year career conducting research in the Arctic, scientist John England also thought that Banks Island was a relatively undisturbed relic of an ancient world. Sometime in the 1990s, however, he and a handful of colleagues in the paleoenvironmental community saw something in the accumulation of geological evidence that suggested that this theory might be flawed.
England and I were standing on the tundra at Ballast Brook, the site of Hills's mammoth bone find, in the summer of 2012 when he described to me how he saw it all unfold. It was cold and bleak that day in August, just as it might have been when Hills had been there more than four decades earlier. England was waving his arms, much like a sketch artist might do in a courtroom, drawing a picture of a monstrous sheet of ice moving north from the mainland in super-slow motion, churning up granite and gravel, sand and stone, and possibly the bones of animals that may have died in its path (Figure 1.1). Banks Island may have been home to woolly mammoths and other Ice Age animals at one point in time, he told me, but if it had been, the animals were eventually displaced by this big sheet of ice.
"If there was such a population, it is surprising that no additional evidence has been found of any other animals like it," he said. "One bone on Melville, one on Banks? And the Melville sample was found below marine limit, the height of the postglacial sea level that inundated the land after ice retreat." He offered a different interpretation of the evidence: "That mammoth bone could have been rafted in by sea ice long after the animal from which it was derived, lived," he added. "How far away is anyone's guess."
England didn't arrive at this theory lightly.
The truth about how Banks Island and other parts of the Arctic have been shaped by climate, glaciers, and ice sheets has been germinating, evolving, and constantly changing as a result of the research that he, Harington, and many other scientists have been conducting in the circumpolar world. It all it points to a region that has undergone massive changes over the eons.
For the longest time, putting together the pieces of the puzzle to get a picture of the past proved to be elusive because radiocarbon dating is generally not reliable for dating anything more than 50,000 years old. Additionally, many important pieces of the puzzle were buried in permafrost, snowpack, and riverbeds in the most inaccessible parts of the world. Those that were found offered only a snapshot, not necessarily strong evidence of the land's complex evolution.
No one in Hills's day, however, expected this once very blurry picture of the past to unfold as clearly as it has. Two Smithsonian scientists, Charles Schuchert and David White, returned from Greenland in 1897 bearing fossils that suggested that the Arctic wasn't always covered in snow and ice and that it was once a tropical paradise forested by giant sequoia–like trees rising up from an undergrowth of luxuriant ferns, tangled vines, and flowerless plants. Foremost among the discoveries that have transformed our understanding of the Arctic as a warm climate since then is Mary Dawson and Robert West's excavation of a rich vein of varied life-forms at Strathcona Fiord on Ellesmere Island in 1970s. In among the rocks, gravel, and peat they dug and sifted through, these American scientists found fossil fragments of alligators, giant tortoises, snakes, lizards, tapirs, hippos, and rhino-like animals that lived 55 million years ago in a climate that was similar to what is experienced today in Georgia and the Florida Everglades.
Equally important were the tree trunks that helicopter pilot Paul Tudge saw sticking out of the ground on Axel Heiberg Island in the High Arctic in 1985. The trees turned out to be more than 10 million years younger than the creatures Dawson and West had unearthed. Some of the dawn redwoods that paleobotanists James Basinger and Jane Francis later found were more than 16 feet long and 8 feet wide. The various nuts, seeds, and cones they collected were so perfectly preserved that they looked as if they had recently fallen to the ground. Several specimens still held the sap they oozed before a catastrophic flood buried and preserved them in an anaerobic tomb of sand. A single tooth found by paleontologists Jaelyn Eberle and John Storer some time later indicated that here was a world that was lush enough to sustain brontotheres, a rhino-like animal that was found in large numbers across Asia and North America.
In the years that followed, a picture of an enduringly warm Arctic came into sharper focus. Brontotheres, we now know, continued to thrive in a mixed conifer forest on and around Devon Island, located to the west of Baffin Bay from Greenland's coast, for several more million years. Four and a half million years ago, miniature beavers and three-toed horses lived in an upland environment at Strathcona Fiord where they were constantly on the lookout for ancestral bears, weasel-like carnivores, and Eurasian badgers that lurked in the adjoining forests 4.5 million years ago. And thanks to a recent discovery by Natalia Rybczynski, we also know that camels lived in the same region in larch-dominated wetlands a million years later.
As warm and verdant as the Arctic was for most of the past 100 million years, a trend to cooling began to take place shortly after smaller mammals replaced the dinosaurs 65 million years ago. The gradual buildup of glaciers and ice sheets that followed 20 million years later signaled the beginning of the end of the brontotheres. By the time miniature beavers had staked their claim at the north end of Ellesmere Island, a vicious cycling of advancing and retreating glaciers had begun to take hold, killing off vast swaths of forests throughout the Arctic Archipelago and northern mainland, including those that grew out of the ground at Ballast Brook.
I had trouble picturing this scenario until I spent several weeks with Jim Basinger at Axel Heiberg and then with Dick Harington at Strathcona Fiord, excavating fossils from stark hillsides of frozen peat and gravel. In both places, it seemed as though the summer was never going to come. The surrounding mountainsides were dusted with a fresh veil of snow, and a wickedly cold wind periodically swept snow squalls and sleet across sea ice that showed no sign of melting. Sifting through the peat on a high hilltop one day with Harington, I picked out a twig that had the bite of a beaver on its tip. Harington took it in hand, looked at it, and then pointed to the glaciers in the distance.
Starting sometime around 2.6 million years ago, he explained, summers could no longer melt the ice and snow that winters produced, and glaciers continued to grow in volume. Weighed down by the mounting snow, these rivers of ice began to slowly slide forward down mountainsides before plowing through forests and fanning across open plains.
So much of the world's water was locked up in ice and snow during most of this so-called Ice Age that sea levels dropped to levels that were up to 400 feet lower than they are today. In time, the shallow submarine world that connected Arctic Russia to Arctic North America was revealed. Attracted to the succulent grasses that rose up from these verdant lowlands, Asian animals like the mammoth, saiga antelope, and steppe bison eventually crossed over to new lands, where they were met by scimitar cats, short-faced bears, and other North American predators.
On one hand, this enormous land bridge functioned as a gateway to new ranges for terrestrial animals, but on the other hand, it was a barrier that blocked whales, walrus, seals, and other marine mammals from migrating back and forth between the Arctic and North Pacific Oceans. The presence of this continent-sized land mass also put an end to the relatively warm freshwater that poured heat and nutrients from the North Pacific into the Arctic Ocean. The Arctic not only got colder, it got drier because so little moisture rose up from what little open water there may have been at the time. Additionally, the mounting sheets of ice reflected the heat of the sun back into the atmosphere.
As cold as it was for most of the past 2.6 million years, there were brief periods of intense warming. During these interludes, giant ground sloths migrated north to the Arctic from South America as did camels, pigs (peccaries), horses, American mastodons, and beavers the size of grizzly bears that lived farther north.
When the warming ended and the ice sheets returned, some of these animals found refuge in places such as the Old Crow Flats of the Yukon that were too dry and cold to grow ice. In time, though, most of the animals were unable to withstand the rapid-fire cycles of cooling and warming that followed. Among the thirteen species of mammals that Harington unearthed at Gold Run Creek in the west-central part of the Yukon Territory in the 1970s, seven of them — the giant short-faced bear, American Beringian lion, American mastodon, woolly mammoth, horse, helmeted musk ox, steppe bison — are extinct. Two others, the American badger and the black-footed ferret, are no longer found in the Arctic.
What we have today are the survivors: a mere 11 Arctic bird species, 357 types of vascular plants, 12 terrestrial mammals, 3 Arctic whales, and a handful of other marine mammals that have found a way to live in the Arctic year-round.
If the past tells us anything about the future, it's that the current migration of deer, cougar, coyote, killer whales, and Pacific salmon into the Arctic is nothing new. Nor is the apparent decline of Arctic animals such as the polar bear, ivory gull, and caribou.
Taking this long view, Yukon paleontologist Grant Zazula believes there is much we can learn from this picture of the past that has been emerging. But he also believes that extinctions, local extirpations, and the like create opportunities for evolution. "Extinction," he argues, "is essential for evolution to be possible. Environmental change works like that too. It might be detrimental to one critter, like warming climates and forest expansion was for woolly mammoths, but it created a great opportunity for giant ground sloths to multiply and expand."
Zazula suggests that we should be careful in predicting who the winners and losers will be over the next 100 years. Many scientists, he points out, think that caribou will be hit hardest by climate-induced landscape changes that are expected to wipe out as much as 89 percent of their habitat. But if the history of caribou tells us anything, he says, it's that caribou managed to find refugia in the Arctic through several periods of glaciation over the past 1.6 million years. The same, he says, can be said about bison, which hung on until 400 years ago when something — no one knows what exactly — wiped out the last of them in the Yukon and Alaska.
Even the woolly mammoth almost made it. Scientist Duane Froese, working with Zazula, geneticist James Haile, and other scientists from Australia, Scotland, England, and the United States, recently found evidence along the Yukon River in Alaska that suggests that the woolly mammoth lived several thousand years longer than previously thought in so-called ghost ranges of the western Arctic.
It wasn't just climate and changing landscapes that killed off the last of the woolly mammoths. Theoretically, humans who crossed the Beringian land bridge 15,000 years or more ago contributed to demise of the woolly mammoth. The prospect of human influence on mammoth populations was nicely articulated in 2011 by palaeoecologist Glen MacDonald and his colleagues at the University of California, Los Angeles after they analyzed radiocarbon dates for mammoth specimens, archeological sites, and prehistoric plants and trees. Mammoth populations, they concluded, didn't go out with a big bang as some had previously thought. Instead, their numbers gradually declined as the Ice Age gave way to a warmer, wetter climate that transformed steppe lands into peat bogs, shrublands, and conifer forests. As the populations shrank into areas that were still covered by grasses and sedges, hunting by both humans and predators took its toll. Slow breeders that they were, the mammoths didn't have the reproductive ability to get out of this predator pit they were in.
The take-home message, says Zazula, who published a wider ranging paper on the subject with a long list of like-minded scientists, including lead author Eline D. Lorenzen, is that each species responds differently to the effects of climatic shifts, habitat redistribution, and human encroachment. Using ancient DNA, species distribution models, and the human fossil record, they concluded that climate change could in itself explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, but it appears that a combination of climatic and anthropogenic effects is responsible for the extinction of others, including Eurasian steppe bison and wild horse. Interestingly, they found no genetic signature or any distinctive range dynamics that distinguished extinct from surviving species.
The big difference between now and then is that there are a lot more people living in or working in the Arctic. And they are not just hunting with spears and bows as they did when the first people ventured into the Arctic world at Yana River in Siberia 35,000 years ago. The prehistoric technology that they brought with them when they made their way across Asia, into Beringia, and then to the Arctic Islands pales in comparison to what people in the North use today. Even then, it seems, they may have helped drive some Ice Age mammal populations that had been pushed to the edge by climate change to extinction. What we consider to be normal wasn't part of the past history of the Arctic.
Today as well, humans are building roads to mine sites, drilling for oil and gas on land and offshore, shipping resources in and out of the region, setting up military bases, and growing their populations in places that may provide refuges for caribou and other Arctic animals that might have trouble adapting to changing land and seascapes.
(Continues...)
Excerpted from Future Arctic by Edward Struzik. Copyright © 2015 Edward Struzik. Excerpted by permission of ISLAND PRESS.
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Table of Contents
IntroductionChapter 1: Eight-Foot-Long Beavers, Scimitar Cats, and Wooly Mammoths: What the Past Tells Us about the Future Arctic
Chapter 2: Oil and Ice
Chapter 3: The Arctic Ocean: A Sleeping Giant Wakes Up
Chapter 4: Stormy Arctic: The New Normal
Chapter 5: The Arctic Melting Pot
Chapter 6: Lords of the Arctic No More
Chapter 7: Caribou at the Crossroads
Chapter 8: Paradise Lost
Chapter 9: Drill, Baby, Drill
Chapter 10: The Need for An Arctic Treaty
Chapter 11: Conclusion
Acknowledgments
About the Author