“We haven’t seen red dragonflies recently.”
We hear such claims in various regions nationwide. Researchers who conducted dragonfly habitat surveys also say the number of dragonflies born in rice fields is declining drastically. They attribute the decrease to the changes in farming and watering methods, as well as pesticide applications to parts of rice fields, but details are unknown. It is necessary to find a way to maintain biodiversity while avoiding putting excessive burden on the agricultural industry.
Dragonflies flying about in a cluster in the twilight are a common sight in the countryside. However, many research papers site drops in the number of dragonflies, and many farmers must be feeling the same way. It is not easy to explain the exact causes, because it is difficult to precisely grasp how much the number declined and when the decrease started.
Red dragonflies lay eggs in rice fields in autumn, and when the fields are flooded in spring, the eggs hatch into naiads. They grow up eating worm fish and in summer they crawl up the rice plants and emerge.
It is true that the environment for naiads, which live in flooded fields, are becoming harsher, as more farmers are adopting rice planting on dry fields to make midsummer drainage easier or changing to upland crops.
At the same time, many point out the effect of pesticides. Newly-developed pesticides are designed to destroy only the selected harmful insects while minimizing unnecessary influence on the environment. New pesticides are registered on condition that their effects on biodiversity are small. However, unlike conventional pesticides, such pesticides are used in low concentration and their effects last for a long period of time, and some believe that such pesticide applications may be causing adverse effects on dragonflies.
It is not easy to come to conclusions on how to apply pesticides. For example, applying pesticides on nursery boxes have largely reduced farmers’ labor burdens. It is not realistic to immediately ban such application across the board, when its effects on biodiversity are yet unclear.
Experts say that reduction in dragonflies can be prevented by changing the timing of pesticide application according to districts or using different types of pesticides. The Environment Ministry plans to start a nationwide survey this year on the effects of pesticides on dragonflies. It is the first time for the ministry to conduct such a survey, and we hope it will lead to new findings.
We also hope farmers themselves will come up with ways to conduct biodiversity-friendly farming in cooperation with pesticide manufacturers. People are not asking only for low-priced, good-tasting rice. They must be looking for rice grown in paddy fields where biodiversity and unique landscapes are preserved. No matter how much rice we eat, we cannot increase the number of dragonflies around us if the rice is imported from the United States or China. We want to make this incident an opportunity to pose a question to the Japanese people. “Will you still ask for imported rice?”
(June 1, 2014)