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Surge in low-quality rice, industry losses if Japan climate change unchecked: research

Immature white grains, left, and regular rice grains, right, are seen in this photo taken on Oct. 3, 2019. (Mainichi/Aya Iguchi)

TOKYO -- If climate change continues at its present rate, harvests of koshihikari, the main rice strain farmed in Japan, are expected to yield around twice the ratio of poor-quality grains in the 2040s than they do now, according to a research team with members from Ibaraki University and other institutions.

The team's findings, which estimate that a consequent drop in prices could bring losses to as high as 44.2 billion yen (around $404 million) across the country, were published in a journal specializing in environmental science.

If average daily temperatures during the about two-week-long grain filling period after ears of rice emerge, reach 26 to 27 degrees Celsius or more, the crop's starch content is reduced. This then leads to greater numbers of grains with a white, cloudy appearance which sees them referred to as "immature white grains."

Immature white grains are considered low-quality produce. If rice grain inspections required by law find over 30% of the product to be of a lower standard, then rice must be sold at a quality rating of 2 or lower, depending on its appearance and other factors. There have also been suggestions that a high proportion of immature white grains affects the taste of rice.

To arrive at its findings, the team put together a hypothesis in which rice is cultivated across all of Japan. They then forecast the rate of immature white grains' appearances per kilometer square.

Their results found that by the end of the 2020s, the rate of occurrence would shift to an average of 6 to 7% nationally. Japan's average August temperatures are projected to rise to a high of 27 degrees C in the 2040s if no strict measures are taken to stop climate change from continuing at its current pace. Under those circumstances, the rate of immature white grains would approximately double, rising to 12.6%.

Additionally, the team analyzed actual inspection results where rates of immature white grains topped 16.9%, and hypothesized that the crop was then given a quality rating of 2. Based on their theory, regions where the average harvest of koshihikari is labeled second-rate or lower were limited just to parts of areas concentrated in western Japan by the 2020s.

But by the 2040s the issue would spread widely, affecting large swaths of eastern Japan -- especially coastal plain regions. Including prefectures such as Niigata in central Japan, a traditional rice belt, the ratio of low-quality produce areas would account for 30% or more of all rice paddies across Japan. It is estimated that the consequent rise in low-quality rice classifications would bring losses in the industry to 44.2 billion yen per year, more than five times their current amount.

With the effects of climate change on the agriculture industry already apparent, development of high-temperature-resistant strains of rice and other schemes are already going ahead in various regions of Japan.

Yuji Masutomi, a member of the research team and an associate professor of agricultural meteorology at Ibaraki University in the eastern Japan prefecture of the same name said, "Some regions have a greater tendency toward producing immature white grains, so it is important to choose areas to prioritize preventative measures. We want our predictive results to be effective for investigations into short- and mid-to-long-term countermeasures."

(Japanese original by Ai Oba, Science & Environment News Department)

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