Climate change is threatening Japan's sushi culture. Here’s how

Sushi is synonymous with Japan. But this hugely popular food is under threat.

For the uninitiated, sushi is bite-sized and rice-based, often involves raw fish and is usually accompanied by sliced ginger and wasabi. Whether you’re a fan of nigiri, gunkan or temaki and buy it from the supermarket or enjoy it in a high-end restaurant, the global sushi market is big business. But climate change is starting to have an impact on the industry.

The global sushi restaurants market is predicted to grow by $2.49 billion by 2025, according to Research and Markets. While in the US alone, the market size of the sushi restaurant sector reached $22.25 billion in 2019, says Statista.

In a 2019 survey, Statista also found that just over two-fifths of Japanese people consume sushi from a shop at least once a month.

However, just because there’s a demand for sushi doesn’t mean that it can be met. In Japan, fishermen and women are worried about stock. In an article published by Reuters, people who have been fishing for years spoke of their concern over an unprecedented number of unusually fatty katsuo.

Otherwise known as skipjack tuna, the fish is a crucial part of Japanese cooking, especially when it comes to sushi. Fishermen believe that the fatty katsuo must be connected to rising water temperatures and therefore climate change. Data from local laboratories shows that the average temperature in a bay in southwest Japan - usually regarded as a profitable fishing area - had, over 40 years to 2015, risen by 2C.

This warmer water presages future problems, not least fewer katsuo. There’s also the existing issue of overfishing which has decimated fish numbers, and a reluctance of younger generations to follow their parents and grandparents into the family fishing business.

And then there are the fears over the future of wasabi amid climate change. In 2019, a particularly fierce typhoon season full of landslides and heavy rains had a catastrophic effect on Japanese wasabi farms.

As wasabi is usually grown along streams in narrow valleys, it is vulnerable to harsh weather. And, as global warming contributes to the frequency and intensity of storms, rising temperatures also risk harming wasabi production. The plants thrive in water which maintains a year-round temperature of between 10-15C. So a combination of all these climate change factors has led to an instability in the supply of wasabi.

As with so many things related to climate change, adaptability is key.

"If this unstable supply of wasabi persists, due to many factors including global warming, we will face a situation where we need to come up with other ways to overcome the problem so we don’t end up not serving raw wasabi at all," Norihito Onishi, head sales manager at a chain of Tokyo noodle restaurants, told Reuters.