News - South China Morning Post
· collected 2026-09-06 · by Julian Ryall
Japan's Hokkaido island is experiencing an unexpected surge in cockroach populations due to rising temperatures and warmer winters caused by global warming. According to Japan Meteorological Agency statistics, the average daytime temperature on the island has increased by 1.5 degrees Celsius over the past three decades. Local resident Makoto Watanabe, who previously considered Hokkaido too cold for cockroaches, now encounters them regularly in his home town of Eniwa. The warmer temperatures have allowed cockroaches to thrive in what was once a relatively inhospitable environment for them.
Written by the local model on 2026-09-06,
using this article's own text rather than the other coverage of the
same event (that is the story summary below).
Story summary
Hokkaido, Japan's northernmost island, has seen a significant surge in cockroach populations due to rising temperatures and "artificial environments" such as buildings and homes. According to the Japan Meteorological Agency, the average daytime temperature on Hokkaido has risen by 1.5 degrees Celsius over the past 30 years, reaching up to 35 degrees Celsius in some areas during summer. This warming trend is attributed to global warming. Residents like Makoto Watanabe, who lives in the town of Eniwa, have noticed the increase in cockroach populations, with some recalling that they were rarely seen on the island even 30 years ago when it was considered too cold for them to thrive.
Written for “Pest Infestation in Japan” on 2026-09-07,
grounded in this article and the 0 other(s) covering the same event.
Why this leaning score
The model judged this article politically coded and scored it +0.35, but every quote it verified points left, so the score is not published.
Written under an earlier scoring contract, which gave a paragraph
rather than checkable quotes. Re-analysing this article replaces it.
Leaning score withheld for article 5539: score contradicts its own evidence · logged 2026-09-06
Japan’s Hokkaido battles cockroach surge amid global warming
asserted
Hokkaido → battle → warming
Rising temperatures and ‘artificial environments’ enable the insects to thrive in a region once considered too hostile for them, experts say
In all his five decades of living in Hokkaido, Makoto Watanabe cannot recall ever being confronted by a cockroach.
asserted
Watanabe → rise → 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.
asserted
Watanabe → use → 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.
asserted
who → move → Eniwa
But Hokkaido has changed in those 30 years.
asserted
Hokkaido → change → 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.
uncertain
temperature → accord → summer
More recently, localised summer temperatures have spiked as high as 35 degrees, a figure that was unthinkable even a decade ago.
asserted
that → spike → degrees
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.
asserted
average → become → January
