Like a scene from a made-for-TV horror movie, more than 70 beach-goers were attacked on Christmas Day when a sudden influx of piranhas swarmed the crowded waters of bathers seeking a respite from the unusually high 100-degree temperatures on the Rambla Catalunya beach in Rosario, Argentina. Seven children lost parts of fingers and toes to the sharp-toothed creatures. Then, just this past weekend, the same carnivorous fish attacked again, injuring 10 downstream in the same river near Buenos Aires.
To be sure, the legends about man-eating piranhas are notoriously overblown—compare, for instance, the numbers in these attacks against the 800,000 Americans who annually need medical treatment for dog bites, and the piranha “threat” begins to pale a bit.
But that doesn’t mean that we won’t be seeing—and feeling—more of them and their kith and their kin in the future.
Across the globe, scientists say, an increasingly warm planet has forced animal populations to abandon their usual hunting grounds in a search of food or a more comfortable habitat, clashing with humans in the process. Bears are lumbering into towns, jellyfish are arriving at coastlines, mosquitoes are swarming northward, and storms are pushing tigers and humans into close proximity. Rising temperatures and environmental decline wrought by climate change makes it seem like a full-fledged animal kingdom revolt is just a couple notches in the thermometer away—and it might be.
Argentine officials theorized that a spike in the weather and a shortage of the piranha’s normal prey sparked the attack, which have apparently been on the rise recently. And biologists say climate change has been destroying the piranha’s home, the Paraná River for years. But it could just be humans and animals are learning what it feels like to step on each others toes.
The American coastline is similarly vulnerable to the underwater predators. In 2012, researchers at the Department of Natural Resources in South Carolina drafted a report predicting an invasion of non-native species like piranha and Asian swamp eels on their coasts in the coming decades due to rising global temperatures. Changes in climate have also contributed to a movement of jellyfish closer to the shoreline in Spain as warm water attracts them and a lack of rainfall dilutes the natural salt water barrier that kept them away from the beach. Inventive solutions to protect beach-goers from jellyfish stings include a jellyfish-shredding underwater robot, and experiments by researchers that could make jellyfish more palatable to humans.
Above water, unnatural animal and human interactions continue to rise. In American bear territory, the lumbering creatures are suddenly roaming out of their normal radius, inspired by a lack of snow and food. A warm winter in the Sierra Nevadas this year has brought black bears—normally content to hibernate from December to March—scampering around populated areas of Lake Tahoe and Yosemite National Park. An uptick in sightings even included a bear ambling across the ski slopes during the Far West Masters race in Tahoe, where a small number of bears have permanently eschewed hibernation in favor of scavenging.
Food and water scarcity during California’s drought, possibly the state’s worst in a century, has also forced the bears out of their normal roaming area and into more populated urban regions closer to humans. This past July, foothill communities in California experienced a sudden tripling of bear sightings, as the animals searched for food after the winter drought. But their wandering ways can be fatal for the bears. In December, Tahoe rangers put down a particularly curious 260-pounder after he ransacked several cars and one home, as they are sometimes forced to do with bears who grow too accustomed to foraging near populated areas for food.
According to Terry Root, a biologist at the Stanford University, creatures adapted to previous changes in climate by migrating. Now, the temperatures are changing faster than ever and there are more roadblocks in their way. “In the past, plants and animals have not had to skirt around areas that humans were occupying,” she says. “Now they have to scoot around farms and highways.”
Though fatal black bear attacks are rare, they are rising as human population increases, according to a 2011 study that examined all deadly attacks in Alaska. The study also noted that bear attacks mostly occurred during August, when bears are gearing up for hibernation and seeking food. “[W]e don't know exactly why there have been more attacks in Canada and Alaska,” Stephen Herrero, professor emeritus at the University of Calgary, said in a statement, “but we speculate that it could be because bears in those areas are living in less productive habitat with periodic food stress, which may predispose some bears to consider people as prey.”
Their all-white relatives are venturing out in similarly dangerous fashion. In colder climates, melting arctic plates has forced polar bears to abandon their ice floes for dry land hunting. And towns on the edge of their range have and will experience more interaction as the bears arrive to scavenge. Sightings in Russia, Canada, and Alaska have been on the rise. In November, two people were mauled in an unusual polar bear attack in the center of a town near Hudson Bay in Canada. The boldness of these encounters has police and scientists nervous. "When we see bears attacking people, that is a very good sign that these are bears that are on the edge," Tom Smith, a wildlife biologist at Brigham Young University, told +The Guardian, noting that a lack of nutrition prompts such risky behavior in the creatures. One bear, he said, recently traveled 250 miles inland to find food—an incredible distance considering the five-mile stretch of coastline within which they normally range. (It's worth noting that on Wednesday of this week, the average temperature in Alaska was higher than in any state in the continental U.S.)
But these sharp-toothed invaders are just a small issue compared to the barely visible creatures swarming northward, according to Miles Grant, senior communications manager at the National Wildlife Federation (NWF). Malarial mosquitoes and Lyme disease-spreading ticks are thriving in the ever-warming climate, arriving in swarms to historically colder regions. “When people think of global warming, they think of far away polar bears and distant glaciers, but the real problem are bugs coming into our backyards,” Grant says.
Between 2001 and 2011, confirmed cases of Lyme disease multiplied by five across the U.K. And according to the World Health Organization (WHO), just a two to three-degree Celsius uptick would bump up the number of people at risk of transmitting malaria by 3 to 5 percent—that’s several hundred million more possible cases. “Trying to get rid of some of these creatures is a herculean task,” Grant says, noting that while mosquitoes and ticks are migrating, the bugs’ enemies are not. The cost of combating these swarms to prevent a public health crisis could be enormous, he adds.
Natural disasters sparked by atmospheric changes can also trigger an animal’s instinct to venture out of its home. In 2008, Cyclone Sidr destroyed the Bengal tiger’s mangrove habitats in the Sundarban forests of Bangladesh, forcing the felines into India to search for food. The monsoon season that year saw six tiger attacks, despite the normal rarity of such incidents in that season. Crocodiles also clashed with humans in the area after migrating into the more densely populated higher ground to escape the floodwaters. A booming population in India has contributed to numerous deaths by wild animal. In July 2011 alone, 16 people were attacked by leopards in rural Indian villages on the edge of forest reserves—a sign of the interspecies neighbors being pushed too close together.
Thankfully, our favorite jaw-clamping horror film villains are yet to make the list of animals that humans will be clashing with more frequently in the future. Despite two years of increased shark attacks in Hawaii and despite media postulation of a connection with climate change, it’s impossible yet to tell if there’s a direct correlation between the attacks and changing temperatures.
“Some species of shark’s movement is greatly affected by ocean temperatures, so we expect that to push animals into areas they haven’t been before,” says Professor Christopher Lowe, director of the California State University Long Beach’s Shark Lab. But scientists have not yet concluded how climate change influences shark migration or even why they attack humans at all. Though, as populations and temperatures rise, he notes, “we’re putting more and more people in the ocean than ever before,” which increases the likelihood of an interaction.
A barrage of animals lashing out due to man-made temperature spikes is a predictable future dystopia of the utmost irony. But as you start building an apocalyptic bunker, don't forget who's to blame for this increasingly dangerous behavior. “We got to sit back and realize that humans are causing it and because we’re causing it, we’re able to stop it,” Stanford's Root says. “We just have to have the political will to do that.”
"Those 1970s 'when nature attacks!' movies never concluded with '… and then we gradually cut carbon pollution and the spiders left William Shatner alone,'" jokes the NWF’s Grant in an email. "But in real life, that’s what we need to do to protect ourselves."