According to experts, rising sea temperatures caused by the climate crisis have killed eight out of ten brown bear pups born this year in a remote section of northern Japan.

Acorns and pink salmon are a significant source of nutrition for nearly 500 brown bears that live on Hokkaido's Shiretoko peninsula, a Unesco World Heritage site famed for its stunning coastline and wild creatures.

According to The Guardian, in July, the average daily surface temperature of the world's oceans reached a record high and is expected to continue to increase as a result of climate change brought on by burning fossil fuels.

The global average daily sea surface temperature broke the previous record of 20.95 degrees set in 2016, according to the newspaper, which also noted that the temperatures are anticipated to rise further because March is typically when the oceans are at their hottest.

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Early this month, Katsuya Noda, a tour boat operator, discovered a malnourished bear cub urgently looking for food, turning over boulders and looking among mounds of seaweed on the peninsula's eastern shore, alarming local officials. 

Pink salmon in the Hokkaido rivers usually stay in the sea during the winter until they lay their eggs between August and October in the Shiretoko streams. Usually, the bears wait to have the salmon as they swim upstream, but a lack of river fish has forced them to swim in the sea.

Noda told the Asahi Shimbun that “some bears have grown really thin,” adding that “they are having a tough time, because there are no fish in the rivers, just like last year.”

According to experts, sea surface temperatures off Hokkaido hovered above 20 degrees Celsius from mid-July to early August 2021, 5 degrees Celsius more than the usual for that time of year.

Hokkaido University researchers have warned that if global warming continues at its current rate, marine temperatures surrounding the island might climb by up to 10 degrees Celsius by the 2090s compared to 1980s levels.

Masami Yamanaka, a researcher at the Shiretoko Nature Foundation, told the Asahi that the lack of nutrition in the cubs was devastating and a "serious" issue, noting that 70% to 80% of those born this year are already dead.

According to the Hokkaido Salmon Propagation Association, fishermen captured 482,775 pink salmon in rivers in Hokkaido, Japan's northernmost major island, compared to 23,298 last year at the same time. 

More bear attacks on humans have also been happening due to the acorn shortage, as bears seek food in inhabited areas. A total of 1,056 brown bears were caught and killed in Hokkaido in the year up to April 2022. A total of 999 brown bears were killed for fear of damage to crops or because they were feared a danger to people.

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