The world’s tragedies often have images that end up defining them: A five-year old screaming in Iraq after her parents were killed by U.S. soldiers. A starving child being stalked by a vulture during a ruthless famine in Sudan. 
 
 A video released this week of an extremely emaciated polar bear has served as a similar purpose: as a rallying cry and stand-in for a largely unmitigated environmental disaster. 
 
 The video was shot by Paul Nicklen, a nature photographer and contributor to the National Geographic magazine for the last 17 years. He is also a biologist by training and the co-founder of Sea Legacy, a nonprofit that uses storytelling and images to advocate for the environment. 
 
 Nicklen’s video, which he shot on a trip for Sea Legacy, depicts an emaciated polar bear, its coat patchy, seemingly near death on an island in a Canadian territory inside the Arctic Circle. It searches for food in a rusted garbage can and chews what Nicklen said was an old snowmobile seat. 
 
 And it struck a nerve. It was viewed more than 3.5 million times in posts on Nicklen’s and National Geographic’s Instagram feeds, according to metrics on the photo sharing site, before picking up news coverage from around the world. 
 
 If you have any conscience at all, this video of a starving polar bear will break your heart. We cannot look away. https://t.co/6xPkl45FLp — Maryn McKenna (@marynmck) December 9, 2017 
 
 In his caption with the video, Nicklen wrote that his team’s members were “pushing through their tears” while documenting the bear. 
 
 “It’s a soul-crushing scene that still haunts me, but I know we need to share both the beautiful and the heartbreaking if we are going to break down the walls of apathy,” he wrote. “This is what starvation looks like. The muscles atrophy. No energy. It’s a slow, painful death.” 
 
 [Without action on climate change, say goodbye to polar bears] 
 
 The photo was shot on Somerset Island in the upper reaches of Canada. Nicklen and his team saw the bear and shot the video from about 400 feet away, he said. Nicklen, 49, who grew up in the region on nearby Baffin Island, said that he had never seen a bear in such poor condition before. 
 
 “We stood there crying — filming with tears rolling down our cheeks,” he told National Geographic. 
 
 He said that the intent behind the footage, which is set over a mournful soundtrack, was not purely journalistic. The trip he was on was part of a push to drive home the issue of climate change with Sea Legacy. Though he said that he had no definitive proof that the bear’s condition was connected to the global phenomenon, he said he wanted to show people what a starving bear looked like and let them draw their own conclusions. 
 
 “We are a visual species,” Nicklen said in a phone interview. “He should have been a dominant bear. Why he was dying, I don’t know.” 
 
 A shot of another emaciated polar bear taken by a photographer in 2015 raised similar questions. 
 
 Polar bears face an existential threat from climate change due to the loss of habitat from melting sea ice, scientists believe. The populations of some 25,000 polar bears in 19 locations worldwide are forecast to decline by as much as a third in the coming decades. As their hunting and breeding grounds shrink, polar bears face an increased threat of starvation. 
 
 More than any other animal, polar bears have become the poster animal for climate change. Former vice president Al Gore used a cartoon of an exhausted, endlessly swimming polar bear to illustrate the impact humans were having on the sea ice where the bears once hunted. And studies and government agencies continue to warn that climate change could make polar bears extinct by 2050. 
 
 A paper published in July said that the higher global temperatures go, the more likely polar bears are to interact with humans — and possibly attack and eat them. 
 
 Some expressed skepticism that anything could be gleaned about the environment from one image. A commenter on the National Geographic’s Facebook page wondered about the bear’s age, when the footage was taken and what an autopsy would show. 
 
 Donald Moore, the director of Oregon Zoo, a senior science adviser to Smithsonian National Zoo and an expert on polar bears, said he couldn’t tell much more about the bear’s age or condition from the video except its extreme skinniness. But he said that starvation was one of the results of the polar bear’s loss of icy habitats. 
 
 “These polar bears should be riding ice somewhere,” he said. “We have seen more and more very thin polar bears in the Arctic in recent years as climate change increases in intensity and opens up more water.” 
 
 He said that the population of polar bears in the wild has declined about 20 percent over the last decade or so. Bears need an immense amount of food, he said, about an average of a seal a week. 
 
 Nicklen said that while most people were supportive of the photo, a small percentage had been offended that he had not taken more action by feeding the bear, trying to save it or putting it out of its apparent misery. 
 
 “It’s not like we travel around with 200-300 of pounds of seal meat when we’re walking around in the Arctic,” Nicklen said. “We knew it was going to be gut wrenching and intense and horrible.” 
 
 Cleve R. Wootson Jr. contributed to this report. 
 
 Read more: 
 
 Polar bears hurt by climate change are more likely to turn to a new food source — humans 
 
 The most accurate climate change models predict the most alarming consequences, study finds 
 
 First a polar bear petted a dog. Then a polar bear did what polar bears do: Ate a dog. 
 
 Love in the time of climate change: Grizzlies and polar bears are now mating ||||| A hard-to-watch video from Canada's Baffin Islands shows an emaciated polar bear in what were likely the last few hours of its life. 
 
 National Geographic photographer Paul Nicklen captured the sad sight on video and posted it online Dec. 5. The video shows the bear staggering toward a trash can and searching in vain for something to eat. It ends with the bear resting on the ground, exhausted. [Gallery: Stunning Photos of Polar Bears in the Arctic] 
 
 Nicklen told National Geographic he wants the footage of the dying bear to communicate the consequences of climate change. 
 
 "When scientists say bears are going extinct, I want people to realize what it looks like. Bears are going to starve to death," Nicklen said. "This is what a starving bear looks like." 
 
 Polar bears depend on sea ice to hunt seals, which fuel the bears with their blubbery, energy-rich meat. As the climate warms, the Arctic has been particularly hard-hit. Arctic sea ice reaches its maximum extents in late winter, typically around March, and melts in the summer, hitting its minimums around September. In recent years, ice has been forming later, melting sooner and covering less area. Record or near-record lows in ice extent have become standard each March, when the Arctic should be at its most frosted-over. 
 
 Here, a polar bear stands on the island of Spitsbergen, part of the Svalbard archipelago, bordering the Arctic Ocean and the Norwegian and Greenland Seas. Credit: Prisma Bildagentur/UIG via Getty Images 
 
 In March 2016, NASA scientist Walt Meier told Live Science that the Arctic has lost about half its volume at its maximum extents since record-keeping began. November 2017 saw an average sea-ice extent of 3.65 million square miles (9.46 million square kilometers), according to the National Snow and Ice Data Center, the third-lowest November extent on average since 1979. 
 
 For polar bears, the loss of sea ice means the loss of hunting grounds. The International Union for Conservation of Nature lists the bears (Ursus maritimus) as "vulnerable," largely because of the loss of sea ice. Already, scientists have found that the loss of ice means polar bears must swim farther for food, a fact that puts cubs, in particular, at risk. Bears must also travel longer distances on foot over sea ice as the drift of the ice increases alongside melt, according to a 2017 study by the U.S. Geological Survey. Another study of bears fitted with tracking collars near Hudson Bay found that bears now spend more time on land, arriving earlier in the summer and leaving later in the fall, a pattern that means their seal-hunting season is limited. 
 
 Though polar bears do shift their diet to snow goose eggs, caribou and other terrestrial meals when on land, a 2015 study published in the journal Frontiers in Ecology and the Environment found that the calories from these sources aren't enough to offset what the polar bears burn in foraging. 
 
 Of course, there is no way to know whether any given bear would have starved without climate change, or what the history of the bear in the video is. 
 
 Shrinking sea ice is causing polar bears to starve more often, but "[y]ou can't say that any one individual is starving because of climate change," Steven Amstrup, chief scientist at Polar Bears International, told Live Science in 2015 after a heart-wrenching photo of a skeletal polar bear circulated online. That's because polar bears do starve in the wild on a regular basis. As apex predators, they have no natural enemies to put them out of their misery when they become too old or injured to hunt, Amstrup explained. 
 
 Nevertheless, Nicklen's video shows what this looks like for bears that have an increasingly hard time hanging on in warming conditions. He filmed the video with tears rolling down his cheeks, he told National Geographic. 
 
 He's been asked why he didn't do something to help, he said, but it's illegal to feed wild polar bears in Canada, and there was little he could have done even if it weren't. 
 
 "[I]t's not like I walk around with a tranquilizer gun or 400 pounds of seal meat," Nicklen said. 
 
 Original article on Live Science.
– An estimated 2.5 billion people saw the image: a starving polar bear struggling across an Arctic landscape. "The mission was a success, but there was a problem: We had lost control of the narrative," writes Cristina Mittermeier in National Geographic. Accompanied by a photographic team, she snapped shots of the dying bear last year while colleague Paul Nicklen shot video—all part of their "mission to capture images that communicate the urgency of climate change," she writes. "When Paul posted the video on Instagram, he wrote, 'This is what starvation looks like.'" He also wondered if all 25,000 polar bears would die like this and urged people to reduce their carbon footprint. But he didn't say climate change had killed this bear. That nuance vanished when National Geographic posted the video with the subtitles "This is what climate change looks like" and the Washington Post ran a dramatic headline about "gut-wrenching" images. People also responded dramatically, expressing gratitude for validation of climate science, anger the crew hadn't fed the bear, or a stubborn refusal to acknowledge global warming. "Perhaps we made a mistake in not telling the full story—that we were looking for a picture that foretold the future and that we didn’t know what had happened to this particular polar bear," she writes. Yet a fast-warming Arctic means bears will be stranded on land, unable to pursue prey, so the photo makes sense. The trick for next time? Make sure "our intentions are clear and the narrative remains our own."