By BRUCE BARCOTT, OnEarth magazine
On a Saturday morning in lateNovember in Kotzebue, Alaska, a village 33 miles north of the Arctic Circle, two Inupiat men nursed cups of coffee at the Bayside Inn. They stared out a window at Kotzebue Sound, an arm of the Chukchi Sea at the southern edge of the Arctic Ocean. Outside it was 35 degrees and raining. “Too warm,” said one of the men.
To get a sense of how that experiment is unfolding, it’s helpful to take a look at one of the most fundamental acts of life: eating, the passage of energy from one living organism to another. Predators and prey form a food chain, plant to insect to rodent to carnivore to apex predator. Those chains interlock to form webs. “To protect Nature,” the conservation biologist Stuart Pimm wrote in his seminal book "Food Webs," “we must have some understanding of her complexities, for which the food web is the basic description.”
Basic is an apt word. Many Arctic organisms are extremophiles — specialists adapted to thrive at temperatures so low they would kill most other species. It’s a club with few members. Species diversity is low, so Arctic food webs are simple. And in the age of climate change, simple is not a good thing to be.
“The more complicated and interconnected the food web, the less damage you can expect if one or two species are lost,” explains Deborah Bronk, a biological oceanographer and specialist in nutrient cycling at the Virginia Institute of Marine Science at the College of William & Mary. “In these very simple food chains, if you lose one species you can really mess up the whole thing.” Complexity yields resilience.
Without resilience, there’s risk of a crash. Scientists who study trophic cascades, in which the loss of a single species sets off a reaction throughout the food web, report that this sort of crash generally happens in low-diversity ecosystems, where one or a few species exert great influence.
That describes the Arctic marine and coastal food web.
During the past few years a number of disturbing reports from the Arctic have appeared in scientific journals. Increasingly acidic seawater may be affecting the ability of crustaceans to form their shells. Warmer-water fish are invading waters traditionally inhabited by cold-water fish. More seal pupping dens are collapsing because of earlier springs and diminished snow cover. Starving polar bears have been seen scavenging berries, grass, moss, and goose eggs. As ice disappears, walrus colonies are increasingly hauling out on land, where polar bears—also on land because of the lack of ice — have been observed attacking them. Humans, a big part of the Arctic food web, are experiencing impacts as well. Their hunting seasons are changing, their travel routes becoming more dangerous and unpredictable. The resilience of the Arctic food web is now being tested. To paraphrase Brendan Kelly: In an ecosystem perfectly adapted to sea ice, snowfall, and permafrost, what happens when those elements begin to disappear?
Kotzebue seemed like a good place to find out. Its 3,200 residents — almost three-quarters of them Inupiat — aren’t mere observers. As Caleb Pungowiyi told me, people in Kotzebue are acutely aware that ice and snow are to the Arctic what soil and rain are to the temperate latitudes.
“We depend on ice freezing up in the fall and the snow accumulating on top of it in fall and early winter” for everything to work, he said. “But now we’re seeing a lot less of both.”
It all depends on ice
Standing in the rain on Kotzebue’s Front Street, a gravel boulevard that curves along the shore, Pungowiyi surveyed Kotzebue Sound. The frozen expanse usually buzzed with snowmobiles. On that day it was silent. “Ice should be a lot thicker,” he said. “Most folks would be out ice fishing for cod and smelt here on the bay.”
What worried Pungowiyi, though, was the action within the ice itself.
Arctic sea ice is a living platform. “When the ice forms, it sustains many things in its own food web,” he explained. “It harbors nutrients and microscopic things. There’s food in there for tiny organisms and little animals. Krill graze on the ice. The ice becomes a critical part of the productivity of the Arctic Ocean.”
What makes that possible are brine channels, networks of needle-thin cracks and tubes that allow hundreds of species of bacteria, fungi, and other single- and multicelled organisms to thrive within the ice. Even during the full darkness of the Arctic winter, bacteria survive by feeding on specks of waste from algae and other organic material trapped in the ice. Sea ice nurtures such a varied menagerie that astrobiologists study it to see how extraterrestrial life might survive in extreme environments.
The real action happens in spring, when the reemergence of daylight triggers a bloom of ice algae, which begins as a thin web and can grow into 10-foot-long strands that sway like curtains from the underside of the ice. If ice is the soil of the polar sea, ice algae are its most important plant — the organic machine that converts the sun’s energy into food.
The ice algae fuel explosive growth among tiny zooplankton, which feed on them. Larger zooplankton like amphipods, pteropods, copepods, and krill all feed on the algae and the smaller zooplankton. At this lower level of the food web, the shrinking summer ice pack is beginning to change things, but not in the way you might expect. Winter sea ice still forms, but ever later in the season, and come spring the algae strands still grow. What’s changing is the chemistry of the sea itself. In particular, ocean acidification is making it more difficult for shelled plankton to form their shells.
Scientists have long believed that sea ice acts like a giant pool cover, limiting the Arctic Ocean’s uptake of atmospheric CO2. Although some researchers question that assumption, it’s true that as summer ice cover has retreated, Arctic waters have become more acidic. And the process is going to accelerate, because cold water takes up CO2 more readily than warmer water. That’s bad news for creatures like shelled pteropods, an abundant and critical food source in the Arctic, because as the ocean acidifies, it becomes more difficult for them to grow their shells.
On the pH scale of 0 to 14, neutral is 7 — pure freshwater. Zero is like battery acid. Most seawater is somewhere around 8, slightly alkaline.Pteropods, pea-size mollusks known as “sea butterflies,” grow their shells by absorbing aragonite. But as seawater acidifies, it becomes undersaturated in calcite and aragonite, forms of calcium carbonate vital to shell formation.
Several years ago, Victoria Fabry, an oceanographer at California State University at San Marcos, noticed that if you drop pteropods in extremely acidified seawater, their shells would begin to dissolve. In 2008, Steeve Comeau, a researcher with France’s Laboratoire d’Océanographie de Villefranche, scooped up some Arctic Ocean pteropods off the coast of Svalbard, Norway. He maintained a control group at the natural water pH of 8.09 and kept a second group in seawater lowered to 7.78, a level of acidity that climate models predict will occur in parts of the Arctic Ocean by 2029. Over six hours, both groups continued to grow their shells — but the pteropods in the more acidic water grew 28 percent more slowly.
The year 2029 may seem remote, but as climate change continues to speed up, long-range predictions have a way of becoming short range. For example, a paper published in March 2009 by scientists at the University of Berne, Switzerland, predicted that aragonite undersaturation would start turning up in Arctic surface waters around the year 2016. But just eight months later, Canadian researchers announced that it was already happening. They had discovered mildly acidified seawater — strong enough to cause concern for pteropods — in the summer of 2008 in the Arctic Ocean above the Canadian archipelago.
That acidified seawater shows up only during summer, when the ocean north of Canada is ice free. But climate modelers predict that aragonite undersaturation will become more widespread. As more of the Arctic Ocean becomes ice free in summer, more acidic seawater may make it harder and harder for some of the most critical feedstocks of the Arctic ecosystem to form the shells that keep them alive.
The amazing blood of the Arctic cod
The Arctic Ocean is so cold that only a handful of fish and marine mammals can survive there. Subsurface temperatures range from 37.4 degrees Fahrenheit on a warm summer day to 28.76 degrees, the freezing point of seawater. In those extreme conditions, one fish species in the center of the Arctic food web is uniquely equipped to thrive: the Arctic cod.
A slender and smaller cousin of the Pacific and Atlantic cod, the Arctic cod is often seen near the underside of the ice, feeding on pteropods, copepods, krill, worms, and small fish. It uses cracks and seams in the ice much as tropical fish use a coral reef: as a refuge from predators. Its survival in these heat-sapping waters depends on two things: blood and fat.
Arctic cod blood is a biological marvel. The fish survives thanks to a special protein that acts as an antifreeze, preventing the blood from crystallizing at temperatures below freezing. As for the fat, it is hard to overstate its importance to the health of the entire Arctic food web. Pound for pound, Arctic cod contain nearly twice the energy of groundfish like pollock, which thrive in the subarctic region of the North Pacific. For animals in the Arctic, where every calorie is dearly earned and spent, that’s a massive bang for the buck.
The Bering Strait acts as the border between the Pacific and the Arctic Ocean. But man-made distinctions mean little in the biological world. What really separates Arctic from subarctic species is the Bering Sea cold pool, a tongue of near-freezing seawater that constantly expands and recedes south from the strait. During warmer summer months, some subarctic species like pollock and flounder can move into Arctic waters, but the winter cold pool eventually drives them back south.
Since the early 1980s, though, the cold pool has been in retreat. Rising air temperatures and the shrinking ice pack have pushed warmer waters more than 140 miles north of the cold pool’s mid-century baseline. At least 23 species in the Bering Sea have marched north, following the warming water. Pollock and arrowtooth flounder migrated 30 miles north. Arctic cod retreated, unable to compete with larger subarctic species.
Not all the news is bad, however. Arctic cod represent a most critical nexus point in the Arctic food web, and their place in the ecosystem has so far been well protected by both human and natural systems. In the past four years, the cold pool has regained some of its lost ground (possibly because of a shift in the Pacific Decadal Oscillation, an El Niño–like pattern of climate variability), but over the long term, fisheries scientists expect the cold pool to continue its northward retreat. There is a limit, though. “Above a certain latitude it still gets dark and cold enough in winter for seasonal ice to form, and that creates the cold pool,” says Franz Mueter, a University of Alaska fisheries biologist who studies the state’s Arctic and subarctic marine systems. “It’s going to be a long time before you see the full year-round expansion of Bering Sea groundfish into the Arctic.”
Also in the Arctic cod’s favor: a fishing ban. To prevent a free-for-all in newly ice-free waters, the North Pacific Fishery Management Council in 2009 banned all large-scale commercial fishing in American territorial waters above the Bering Strait. Perhaps most important, the ban covers not just fish but “all other forms of marine animals and plant life.” That may forestall the kind of trouble now brewing in the waters around Antarctica, where a fast-growing industrial krill fishery (it’s sold as food for farmed salmon and pressed into oil for omega-3 supplements) threatens the base of the food chain in the southern ocean. Krill are less abundant in the Arctic, but the growing demand for the crustaceans could lead krill processors to turn their eyes to northern waters.
“Fishermen are frontiersmen,” said Caleb Pungowiyi, who was among those who fought for the ban. “They want to expand their territory. Before you allow any industrialized fisheries in the Arctic, you need to know the science on the stocks, how they can be sustainably fished.”
The ban isn’t written in stone. It’s designed to prohibit fishing until biologists can get a better handle on the Arctic Ocean. But for now at least the Arctic cod —a nd the creatures it eats — won’t have to dodge any trawl nets.
Why the seals need snow
To follow the web to the next trophic level — seals — I hopped a plane to Fairbanks, about 400 miles east of Kotzebue, and met with Brendan Kelly at the University of Alaska. Kelly has been studying Arctic pinnipeds (seals and walrus) for more than 30 years. I caught up to him in a forest of white spruce at the edge of the campus, where he was training one of his seal-sniffing Labradors. Every spring Kelly uses a team of dogs to locate ringed seal pupping dens, which are hidden in snow caves on sea ice.
“Nachiq!” he called out, using the Iñupiaq word for ringed seal. “Find the nachiq.” A young Lab bounded through the trees, trying to pick up the scent of a seal flipper Kelly had hidden. The dog found the flipper and presented the slobbery treasure to the professor.
“See these growth rings?” Kelly said, pointing to faint stripes on the inch-long flipper claws. “They indicate this seal was…let’s see…5, 6…7 years old!”
Ringed seals are small, as seals go, but they are the most numerous and widely distributed pinnipeds in the Arctic. They’re one of the few animals whose range extends from Alaska’s Aleutian Islands, in the North Pacific, all the way to the North Pole. They eat just about anything in the water column — worms to pteropods and krill — but they prefer fish like Arctic cod.
The ringed seal’s numerical and territorial success can be chalked up to those sharp, tough claws. “They use them to maintain breathing holes in the ice,” Kelly told me. During autumn and winter, a ringed seal will maintain six or more breathing holes, sometimes visiting them several times a day to poke and scratch away the ice.
Ringed seals can claw through ice, but they can’t create ice. Or snow. Two weeks after we spoke, the National Oceanic and Atmospheric Administration (NOAA) proposed listing both ringed seals and bearded seals as threatened under the Endangered Species Act — a proposal based in large part upon Kelly’s research. The two species would be the first after the polar bear to be listed as a direct result of global warming. NOAA, which is responsible for threatened and endangered marine species, is expected to make its final decision on the listing later this year.
How did the ringed seal go from healthy and abundant to threatened, seemingly overnight? Loss of sea ice, of course — but also loss of snow.
Ice is important to ringed seals because they almost never come ashore. They use sea ice for resting, molting, escaping killer whales, and nursing their young. “The seal’s situation with ice is kind of analogous to a large population of fish in a lake,” Kelly explained. “Start draining the lake, and at any given point the fish may remain numerous. But so long as the lake continues to drain, you reasonably would have to conclude that the fish are threatened.
“It would be unwise to wait until the fish were in low numbers to conclude that further draining was a serious conservation concern,” he added.
The surprise with seals is how reliant they are on snow cover. In early spring, a pregnant ringed seal will hollow out a snow cave around one of her breathing holes. “They can haul up onto the ice and still remain completely encapsulated in the snow,” Kelly said. Ringed seals give birth and nurse their pups in these cozy subnivean — that is, under snow — lairs. Outside it can be a killing 60 or 70 degrees below zero Fahrenheit, but in the lair it’s a comfortable 23 degrees above.
Of course, carving out a snow cave requires deep snow. “And that,” said Brendan Kelly, “is the problem.”
Arctic snow cover in June — when seal pups still need the protection of their lairs — is about half what it was 45 years ago. Rain and warmer temperatures in the spring bring an earlier snowmelt, which destroys the lairs and exposes the pups to extreme cold and predators like polar bears, Arctic foxes, and even ravens. With their powerful sense of smell, polar bears can sniff out intact lairs, too, but it takes time for them to dig through the snow, giving pups a chance to escape. In years when lack of snow cover has forced ringed seals to raise pups in the open, nearly every pup has been eaten.
A large portion of the Alaskan Arctic snowfall comes in late autumn, in November and December storms. When snow falls on ice, it sticks and accumulates. But during a warm autumn, it falls on open water.
Nearly an inch of rain fell on Kotzebue during my five-day visit. Instead of falling as 10 inches of snow, that precipitation was all lost as water. Worse, the warm air and rain melted three feet of existing snowpack, leaving a net loss of nearly four feet—that much less snow for pupping lairs six months from now. Come spring, that weather anomaly could be a death sentence for a seal pup.
The bears’ race against time
Ringed seals and other ice-associated pinnipeds aren’t merely the polar bear’s prey. They’re its raison d’être. Fossil and DNA records suggest that the white bears began diverging from brown bears around 200,000 years ago. “Some brown bear populations figured out that all these little sausages were available out there on the ice,” said Kelly, “and with their powerful noses, the bears could easily smell out the seals.”
Brown bears, especially the North American grizzly subspecies, are famously omnivorous. Their food web ranges from roots and berries to salmon and deer. Diet largely determines their size. The Kodiak subspecies is the largest — they rival polar bears in size — because Kodiaks consume massive amounts of southwestern Alaska’s protein- and fat-rich salmon.
Polar bears, by contrast, subsist almost entirely on Arctic ice seals, chiefly ringed and bearded seals. No other food comes close to providing the amounts of fat the bear needs to survive the Arctic’s extreme cold. “To a polar bear, seals are giant fat pills swimming around out there,” says Steven Amstrup, a former U.S. Geological Survey wildlife biologist who is now the chief scientist for Polar Bears International. Amstrup has been studying the Alaskan population for more than 30 years. The Department of the Interior relied heavily on his research when it conferred threatened status on the bear in May 2008. Amstrup has predicted that two-thirds of the world’s polar bears could disappear by 2050 if greenhouse gas emissions continue to climb at their current rate.
If polar bears evolved from brown bears, and brown bears thrive in a land-based food web, it’s natural to wonder whether polar bears could adapt by expanding their diet. Researchers have, over the years, recorded a number of instances of gastronomic experimentation by these innately curious creatures. They have been seen feeding on white whales, narwhals, walrus, little auks, Brent geese, thick-billed murres, and ptarmigan. Biologists in Svalbard, the Arctic archipelago north of Norway, have reported polar bears stalking and killing reindeer. During late autumn, when the bears of Canada’s Hudson Bay gather near the water’s edge in Churchill, Manitoba, to await freeze-up, they’ve been observed eating berries, grass, moss, lichen, and marine algae. Canadian researchers recently reported that in the springtime the Hudson Bay bears are increasingly raiding eggs and chicks from the nests of snow geese and thick-billed murre.
The polar bear’s food web may be expanding, but experts like Amstrup see the bear’s behavior as an expression of desperation, the equivalent of a polar explorer eating his shoes. Fat is the key. Even if skinnier, less insulated polar bears were to survive, reproductive rates would plummet. Female polar bears only bear cubs when their bodies have sufficient fat stores; when the fat’s not there, the bear’s body reabsorbs the embryo.
Looking for the polar bear to survive by expanding its food web, Amstrup concluded, was a fool’s gambit. “We just don’t see any evidence that suggests there’s any prey on land that’s abundant enough to support polar bears in anything like their current population,” he says.
Could polar bears adapt through interbreeding? Reports of polar bear–grizzly hybrids obtained from hunters in the Canadian Arctic have raised questions about a possible increase in interspecies breeding driven by climate change. A recent article by Kelly in Nature highlighted confirmed reports of two “grolar bears.” One was a second-generation hybrid, which indicates that the cross-species bears can survive and reproduce. “The rapid disappearance of the Arctic ice cap is removing the barrier that’s kept a number of species isolated from each other for at least 10,000 years,” Kelly told me. Pinnipeds, he believes, are especially strong candidates for hybridization, because many species have a similar number of chromosomes. “By melting the seasonal ice cap,” he said, “we’re speeding up evolution.”
Does that leave a way out for the polar bear? They are spending more time ashore, after all, where they’re likely to encounter brown bears. Prior to the mid-1990s, more than 60 percent of the Beaufort Sea population of polar bears along Alaska’s northern rim denned on sea ice. Now about the same proportion den on land.
Both Amstrup and Kelly say that scenario is unlikely. “Polar bears will starve long before they’re flooded by grizzly genes,” Amstrup told me.
“People often talk about species adapting to climate change,” Kelly added. “But the kind of adaptation that’s necessary is a change toward genes that fit the new climatic environment better than the old genes. Individuals don’t adapt genetically. Populations do. That requires generations, which requires time. Bears, seals, whales — these are long-lived animals. They need centuries to adapt. But we’re talking about losing the Arctic summer sea ice in a matter of a few decades. So the time for adaptive response may not be there.”
The human habitat
Back in Kotzebue, water ran off roofs as if poured from pitchers. The warm rain made the sea ice so dangerous that the town’s radio station, KOTZ, broadcast a public warning. “We have a matter of life and death with the thin ice,” the announcer said.
At the Nullagvik Hotel, a once-proud establishment frayed with rough use, William Berikoff waited for a bush pilot to take him home to Noatak, a village across the sound and up a recently unfrozen river. He had come across the ice a few days earlier on his snowmobile. Now, like many, he was stranded. “Nobody’s going anywhere,” he told me. “Ice is too soft. Hit a weak spot and ptuu,” he said, his hand tracing the arc of a snowmobile sinking to the seafloor.
I walked down Kotzebue’s slushy Front Street to Alex and Siikauraq Whiting’s house, a modern rambler with an Arctic Cat snowmobile parked out front. Alex is the environmental specialist for the Kotzebue tribal government. His wife is the mayor of the Northwest Arctic Borough, a county-level municipality that encompasses an area the size of Indiana. For more than a decade, Alex has been both using modern scientific tools and tapping the memories of elders to mark the effects of climate change in the Arctic.
“Come on in,” Alex said. “I’m cooking some moose stew for lunch.”
He stirred the stew while Siikauraq finished up a phone call. “This is where the food web meets the pot,” Alex said, lifting a spoon to his lips.
People in Kotzebue are extreme locavores. More than two-thirds of their diet comes from the Arctic Ocean and the frozen tundra. The average Kotzebue household harvests 3,000 to 5,000 pounds of wild meat, fish, and eggs every year. That represents more than one million pounds of biomass. “Caribou and moose, those are our beef,” Siikauraq told me. “This moose that Alex harvested, we’ve got 400 pounds of it in our freezer. It’s what we use in tacos, hamburgers, and spaghetti sauce.”
Alex set a bowl of moose stew before me. It tasted like mild venison.
“Our traditional foods are a big part of our culture and identity,” Siikauraq said. “Our elders, when they are sick, they don’t want microwaved pizza. They want fish broth. They want food from the land and sea. I feel it myself. The other day I was desperate for seal oil, my body just craved it. It’s not just food. It’s a medicine for your soul.”
“Seal oil?” I said.
“You should try it,” she said, putting some frozen white fat on the stove to melt. Alex hadn’t hunted seal in a while, so her supply came from a friend.
A lot of food gets distributed like that in the Arctic. John Chase, a colleague of Alex’s, often hunts caribou. “Sometimes I’ll trade the meat for herring eggs or halibut,” he told me one day, “but mostly I give itaway to the elderly folks.”
The subsistence harvest isn’t just about culture. Economics plays a big part. Shipping costs are so prohibitive that a gallon of milk costs $9.79 at the AC Value Center on Bison Street. Most families, like the Whitings, fill their freezers with wild caribou, moose, and seal meat.
The warming of the Arctic, especially the late freeze-up of sea ice, hasn’t cut humans out of the food web. But it has warped things. Seal hunters, who work from skiffs, now have a longer autumn season. The late freeze-up means ice fishers miss the big smelt run in early autumn. On Kotzebue Sound, incomplete freezing can allow storm winds to push loose ice on top of other ice, causing it to stack and refreeze into piles similar to pressure ridges. That makes travel by snowmobile and dog team rougher and riskier.
In native villages like Kivalina and Point Hope, just up the coast from Kotzebue, people use ice cellars (root cellars dug into the permafrost) to store frozen whalemeat and muktuk (whale blubber). Now those staple foods are beginning to turn rancid as the permafrost thaws. Locals can either forgo the food or invest in chest freezers. But diesel-generated electricity costs 50 cents per kilowatt hour — about four times what most people pay in the Lower 48. The ice cellars are — well, were — free.
The most fragile web
In "The Diversity of Life," E. O. Wilson described the removal of a single bird species from a temperate marsh as a way of illustrating the resilience of a complex food web. “That food chain is broken, but the ecosystem remains intact, more or less,” he wrote. “The reason is that each species in the chain is linked to additional chains.” The larger web can absorb the loss of a single link.
That may not be so true in the Arctic. The world’s most biodiverse temperate and tropical forests can contain 10,000 to 45,000 species of vascular plants. In the Arctic, there are about 2,200. In Central America, there are more than 2,800 species of non-fish vertebrates (mammals, birds, reptiles, and amphibians). In the Arctic, there are 322. Nearly an entire trophic level — seals — is dependent on ice, so if the ice goes away, so do the seals. Polar bears depend on three species of seal for survival. That’s it. There is not a lot of redundancy built into the system.
Much of what we know about food webs comes from the study of past top-down interruptions. In the American West, ranchers and farmers extirpated the gray wolf, resulting in a boom in deer and elk populations, which in turn changed vegetation patterns across the landscape.
What we’re seeing now is something new. Near the top of the Arctic food web, polar bears and ice seals are facing dire pressures from humans, but not from hunters with rifles. Our industrial gases are undermining the top of the food web by destroying habitat, melting the sea ice and thinning the snow cover. That results in few direct hits, of course. Some adult bears starve, but mostly it’s an invisible decimation of the next generation. Skinny polar bears don’t produce cubs. Ringed seal pups without snow cover get eaten.
At the bottom of the food web, where species populations are usually checked more by food supply than by predation, the pulse of change is faint but ominous and steadily quickening. The base of the Arctic cod’s food supply — pteropods and other plankton — are finding it more difficult all the time to create shells from seawater. At a certain point, pteropod larvae may be unable to form them at all, and then they will simply wither and die. Whether other plankton, more adaptable to acidified seawater, are able to take their place in the food web remains to be seen.
In Kotzebue today, all that’s visible to the naked eye is the rain. Incessant, warm, dreary rain. It came down in a light spatter as the Whitings and I sat through the afternoon, talking and eating celery dipped in seal oil. Thicker and more buttery than olive oil, it has a gamey tang that reminds you it came from a wild creature raised on fish. It hits the body like a shot of pure fat. In the Arctic a shot of pure fat is a shot of energy, of survival.
We finished off the seal oil. Daylight bled out of the sky and the rain continued to fall, melting more snow with each passing minute.
For more, see Infographic: The fraying Arctic food web.
This article is provided by NRDC's OnEarth magazine. It appears in the magazine's Spring 2011 issue and online at onearth.org.