March 3, 2011
The Faces of Climate Change
Global warming creates a new set of threats to species around the world
by Karen E. Lange
Behind the dire predictions of species extinctions, individual animals are already struggling to cope with a climate transformed. Long in retreat from growing human numbers, now they must adapt to the results of global warming: radically altered habitats, diminished food sources, new predators, and increased risk of disease. It’s up to us to save those who remain.
In the early 1990s, researchers trying to save endangered monk seals in the Northwestern Hawaiian Islands watched puzzled as a growing number of the animals suffered and died. First, a tiny islet the seals had depended on to haul out, give birth, and nurse pups washed away, forcing the group to move to a less protected spot where sharks attacked. The researchers found pups with bite wounds and back flippers torn off, dead pups, and pieces of pups—when the sharks left anything at all.
Then, surviving pups who had formerly been plump and extraordinarily healthy started losing more and more of their fat, says Tim Ragen, who helped conduct the research and now heads the federal Marine Mammal Commission. “As pups lost weight, they lost girth. Bones protruded. They had less energy,” says Ragen. “Eventually, they got to the point where they could no longer forage. We saw them lying on the beach wasting away—and then they died."
Scientists tried to save the seals by hand-feeding them, fattening them up, and moving them to better locations—with mixed success. Starting at a place called French Frigate Shoals, first-year survival rates for juveniles dropped from 90 percent or better to no more than 30.
Part of the reason, Ragen and others now believe, may have been climate change. Global warming could be to blame for the sea level rise and the disappearance of the islet underwater. And it could have hurt the seals in another way: Recent studies in the Central Pacific Ocean have revealed a dramatic drop in productivity—the food available to creatures in the ecosystem. Over a relatively short period, climate change may well have joined with other human-caused threats to alter the monk seals’ habitat and food supply in ways to which the animals could not adjust.
“To survive, an animal must maintain a positive energy balance—take in at least enough energy to support itself and its growth and reproduction,” says Ragen. If they cannot, he adds, “they lose their energy reserves, their ability to forage, and their ability to maintain their health and condition. Eventually, they cannot support life itself and they die.”
The U.N.’s Intergovernmental Panel on Climate Change estimates that 20 to 30 percent of species are at risk of extinction due to global warming. As alarming as those projections are, they mask the individual plights of animals in radically changed environments. For many of these animals, a man-made problem has become a natural disaster. On the level of individual creatures, gut-wrenching dramas are playing out. Unlike Hollywood scenarios of apocalyptic climate change, the devastation is taking place off-screen, out of view of most of the world’s people. Animals are struggling and, often, failing to survive. And the losses aren’t in some future time. They’re happening now.
Global warming is striking polar regions—and animals—first and hardest, as snow and ice melt earlier and reappear later, reflecting less of the sun’s light and uncovering expanses of darker land and ocean that absorb more heat. In the Arctic, temperatures have risen at almost twice the rate as elsewhere on Earth. Polar bears have become the poster child for animals threatened by climate change.
Recent TV commercials featuring the plight of polar bears have made it look as if they are in danger of drowning. Actually, it’s more complex. Sea ice is melting sooner, leaving bears fewer and smaller platforms from which to hunt ringed seals, their primary prey; they need to kill an average of 45 a year to survive, according to a study by polar bear expert Ian Stirling and researcher Nils Are Øritsland. With shrinking opportunities to hunt and fewer ringed seals to prey on, polar bears are going hungry—sometimes even turning up in towns looking for food. Fewer females are in good enough condition to reproduce and fewer young bears are surviving into adulthood. Adding to the stress on the species is unrelenting pressure from trophy hunters, who shoot hundreds of bears each year for rugs and other home décor. For individuals, it’s a story of weight loss, increasingly rare pregnancies, and malnourished young who often don’t survive. In a word: Starvation.
Wildlife photographer Daniel J. Cox has witnessed the gruesome results of starvation firsthand. Filming in Canada last year, he came upon an emaciated polar bear mother and her two malnourished cubs huddled in a snow bank against the wind. The mother barely had enough energy to drive off another bear who approached, presumably to eat her young. Then, as Cox filmed, one cub rose up and went into convulsions. The mother lay listless, helpless, as her cub was dying.
This sad scene is being replayed across other Arctic species. Walruses, for example. Until now, these big, bulky creatures have conserved energy by riding pieces of ice to scattered shallow water feeding grounds where they forage on clams, crabs, and other invertebrates. Diminished ice forces walruses to swim farther out to find food, depleting their energy and fat reserves.
During the summer of 2004, the sea ice retreated particularly fast from the Western Arctic, and researchers spotted calves swimming in deep waters by themselves or in pairs, apparently unable to keep up with their mothers and the rapidly receding ice. Usually, marine mammals approach research vessels out of curiosity and then swim away again, says Carin Ashjian, an associate scientist at Woods Hole Oceanographic Institution. But these calves stayed beside the ship, barking, for hours.
“We realized we were witnessing something that wasn’t normal,” Ashjian says. “ … They should have been with their mothers—they were nursing. We all felt bad. But there wasn’t anything that we could do.”
Increasingly, when exhausted walruses look for a place to rest, they must turn to land because there’s no sea ice to be found. Tens of thousands now crowd together on narrow beaches along the coasts of Alaska and Russia. If the animals are spooked, they stampede toward the water in a killer rush that leaves the smallest crushed, suffocated, or crippled with broken bones. The U.S. Fish and Wildlife Service and U.S. Geological Survey have documented hundreds dead. Reports from Russia tell of thousands.
South of the Arctic, scientists are starting to see evidence that global warming will hurt many bird species. In Europe, 75 percent of common bird species studied by scientists are declining in numbers because of climate change, according to a 2009 report published in the journal Public Library of Science ONE. Exactly why isn’t clear. Presumably, climate change is causing them to lose habitat. Some scientists expect that global warming will also throw off the delicate timing of bird migrations. Birds will continue to fly north at their usual time, while their food supply—swarms of newly hatched insects, say—peaks ever earlier. In such a scenario, by the time birds arrive or their young hatch, the mainstays of their diet are long gone.
Animals who depend on small and specific food supplies and habitats—often already threatened or partially destroyed by human activities—will have the smallest safety net. In North America, researchers are worried about “specialist” birds with particular diets or habitat requirements: The common nighthawk, for example, has already disappeared from much of the northeastern United States; scientists suspect this ground-nester’s absence in the region can be blamed on a drop in the number of gravel roofs that once served as nesting sites. The birds are still found in Southwest grasslands, but researchers fear that a combination of increased drought and fire will disrupt populations of insects that sustain them.
Until recently, animals have generally adapted as the Earth's climate turned warmer or cooler, dryer or wetter. But change is coming too fast now. In the mountains, global warming is shrinking the already meager ranges of animals who live on the slopes. As temperatures rise, shifting habitats uphill, animals can’t always move with them. Wolverines adapted to deep snow packs and cool year-round temperatures may find they have nowhere to go as the air warms and snow melts entirely from peaks such as those in Montana’s Glacier National Park (see "Spirit of the Wolverine"). Pikas, little round-eared, rabbit-like creatures who live on rocky slopes called taluses, may not find the right terrain farther up the mountainside.
To give such animals a way out, people will have to provide natural corridors allowing them to move between increasingly isolated fragments of habitat and, when necessary, travel long distances to new hunting or feeding or breeding grounds, says Michael Soulé, who is known as the father of conservation biology and serves as the Wildlands Network’s vice president of conservation science. “Maintaining the capacity for creatures to move is going to be essential if we’re going to save much of nature on this planet.” With climate change, he says, “things will become less predictable and more extreme. Some places there’ll be floods and hurricanes. Other places there’ll be more drought. A lot more animals will suffer. A lot more will go extinct.”
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At this point, global warming can’t be immediately stopped. But its pace can be slowed. And both the size of future temperature increases as well as the number of years before the world reaches a new equilibrium can be reduced. This is what must happen in order for species to be able to adapt and endure, according to a 2009 report from the International Union for Conservation of Nature. Polar bears, for example, could survive across most of their current range if greenhouse gas emissions peak by 2020, then drop substantially, says a December report in the journal Nature. The bears’ survival will also require an end to trophy hunting. “We still have the physical ability to achieve these targets … if only we have the political and social will,” says Steven Amstrup, lead author of the study and a senior scientist at Polar Bears International. “If polar bears are written off, much of life on Earth as we know it is also written off.”
Already, Ragen says, scientists are regularly confronting exactly the wrong kind of surprise: evidence that climate change is causing even greater environmental devastation than expected. The human species needs to bring its population growth and CO2 output in check, and do so quickly, he says, or the planet will suffer a terrible and irreversible loss.
“Eventually, we are going to be sustainable,” he says, explaining that human beings will be forced to adjust their lifestyles so they and the planet can survive. “The question is: ‘What will be left when we get there?’ ”