The strange reason why bears are attacking people in Japan

It’s a scene from a nightmare: You’re shopping at the supermarket on a normal fall evening, and suddenly a hungry bear walks in and starts smashing things. 

This scene has become a reality in parts of Japan. Last year, in a city north of Tokyo, an adult bear entered an open grocery store, “rampaged” through the sushi section, and, according to a store employee, knocked over and smashed a pile of avocados. The animal became agitated and injured two people, local officials said.

Other stories of recent bear encounters in Japan come to a more harrowing end. In October, local police in Iwate Prefecture, a region in northeastern Japan, reported that a man was out foraging mushrooms in the forest when he was killed by a bear. A few months earlier in a different region, a bear killed a hiker — and data from his smartwatch later revealed frightening details surrounding his death. 

These examples point to one fact: Japan has a bear problem, at least in the north.

In 2025, bears killed more than a dozen people in the country and injured more than 200 others. That’s way up from the previous record, set in 2023, of six deaths. The threat grew so severe last fall — when bears are out looking for more food in preparation for hibernation — that the government called in the military, deploying troops to help trap bears in the northern prefecture of Akita, the epicenter of the attacks. In November, meanwhile, the US Embassy in Tokyo issued a rare “wildlife alert” warning US citizens to watch out for bears.

Most of the recent incidents involved Asiatic black bears, which are not normally aggressive, according to Hengjun Xiao, an environmental researcher at Japan’s Keio University. That makes what he describes as the recent “bear crisis” all the more extraordinary. 

So what’s going on? 

That’s a question that Xiao, a doctoral researcher, and his colleagues tried to answer in a new paper, published earlier this month. It offers a compelling answer — and a clear warning, revealing an unexpected consequence of our changing climate. 

The strange connection between clouds and bear attacks 

Scientists and spectators previously proposed a range of explanations for the uptick in fatal bear attacks. Some have suggested that as Japan’s population ages, fewer and fewer people are living and farming in the countryside around cities. That has allowed natural vegetation — i.e., bear habitat — to grow back, meaning bears are inhabiting land closer to human settlements. 

Other people have pointed out that the number of hunters in Japan is shrinking, too: There are around half as many licensed hunters in Japan today as there were in 1970. So bears are losing a predator of their own. 

These reasons are useful but incomplete — they don’t explain why black bears are attacking people, or why the number of incidents exploded so much last year.

Xiao’s study helps fill in the gaps. By analyzing climate and satellite data, Xiao found that a weather anomaly tied to climate change may explain the deadly surge.

The details are complex, but the new paper — as well as a much lengthier, unpublished study that’s currently under peer review — suggests that climate change is weakening winds, known as the westerlies, that bring dry air into Japan and prevent moist air from the Pacific from flooding in. That’s making northern Japan cloudier. 

With more clouds, less light reaches the forest. And this is key: Without light, forests fail to produce young shoots, nuts, and other foods that bears rely on, the study argues. That leaves bears hungry and likely to venture into human settlements in search of sustenance. Last year, Akita, the epicenter of bear attacks, “endured one of its darkest springs in recent memory,” the authors write, and beech trees in northern Japan produced almost no nuts.

Remarkably, this research essentially suggests that an abundance of clouds — a drop in sunlight — fueled the recent bear attacks in Japan. What’s more is that Japan should expect more of this forest-dimming phenomenon in the years to come, Xiao said, as the planet warms. 

“We are now at a critical point,” Xiao told Vox. “The bear attacks last year are just a warning. There will be more and more of this sort of thing in the future because of the increasing of clouds.”

A warning of what’s to come

Rising global temperatures impact the planet in a number of well-known ways, from fueling extreme wildfires and hurricanes to raising sea levels. But some of the consequences of climate change are more hidden — and they include a spike in human-wildlife conflict. 

Japan’s bear crisis is just one example of many, said Briana Abrahms, a researcher at the University of Washington who studies human-wildlife interactions. “This case in Japan is really indicative of a broader global pattern,” said Abrahms, who was not involved in the new research. 

A few years ago Abrahms published a paper showing how climate change is amplifying human-wildlife conflict around the world — by altering where animals live, when they’re active, and how they behave. During droughts, for example, elephants have entered villages searching for water. Forest fires, meanwhile, have pushed tigers closer to human settlements. And marine heat waves can alter whale migrations, heightening the risk of ship collisions.  

Similarly, rising temperatures can affect human behavior in ways that make us more likely to encounter wildlife, Abrahms says. When crops fail during an extreme drought, for example, farmers might instead forage for food in nearby natural forests, where they’re more likely to encounter dangerous animals like bears. 

“It’s really important for people all around the world — whether they live in the US or Japan or elsewhere — to be aware of these connections between climate events and changes in human-wildlife interactions,” Abrahms said. “Knowing that connection with climate can help us anticipate where and when conflicts are more likely to arise.”