Hokkaido's warming climate brings cockroaches to regions once too cold for them

In all his five decades of living in Hokkaido, Makoto Watanabe cannot recall ever being confronted by a cockroach.

“When I was a university student in Tokyo 30 years ago, I used to see them in my accommodation and I absolutely hated them,” Watanabe told This Week in Asia.

“Since I moved back here, I have always thought that one of the big advantages of living in a place where it is so cold for much of that year is that there are far fewer insects, but cockroaches in particular,” said Watanabe, an academic who lives in the town of Eniwa.

But Hokkaido has changed in those 30 years. According to Japan Meteorological Agency statistics, the average daytime temperature across the nation’s most northerly main island is 23 degrees Celsius (73.4 degrees Fahrenheit), rising to 29 degrees in major cities such as Sapporo, in the summer. That is 1.5 degrees higher than three decades ago.

More recently, localised summer temperatures have spiked as high as 35 degrees, a figure that was unthinkable even a decade ago.

Winter temperatures have also become milder, with the mean average at minus 3.7 degrees in January 1996, but up to minus 2 degrees in January this year.