With COP 10, the international conference on biodiversity held in Nagoya last fall, still fresh in memory, Japanese residents now face a prime example of the importance of biodiversity in nature — the arrival once again of the hay fever season.

Before World War II, Japanese homes used charcoal for heating but switched to oil after the war and demand for trees associated with charcoal production steeply declined. Therefore, in the 1950s and 1960s it was national policy to plant forests of Japanese cedar trees (sugi) and Japanese cypress trees (hinoki), as they grew rapidly and produced hardwood for housing. With trade liberalization, however, cheaper hardwoods from Southeast Asia flooded in and the cedar and cypress forests were left to grow unchecked, emitting masses of pollen each spring.

This year the pollen crop is expected to be unusually large because of the record high temperatures last summer — two to 10 times greater in volume than last year, depending on the area. In response Japanese newspapers have published “pollen front” maps; pollen forecasts are included daily in the morning editions and are updated frequently on various websites. Special displays in drugstores and convenience stores feature a variety of masks (a new one pledges not to smudge makeup), goggles, and nasal creams and gels to keep out pollen. Air filters are popular for home use and special nonstick anti-pollen coats are also available.

The ultimate countermeasure is of course to diversity Japan’s woodlands. Efforts in this area appear to be proceeding slowly. Tokyo started a 10-year program in 2006 to cut down mature trees emitting large amounts of pollen and replace them with varieties of cedar producing much less pollen. The national Forestry Agency is also planning to start a preliminary project in Gunma Prefecture in the next fiscal year to cut down cedar and cypress trees; it hopes that allowing other trees to grow naturally in their place will reduce pollen and provide a natural habitat for more diverse plant and animal populations.

Such efforts will require at least a decade, probably several decades, to show results. In the meantime Japanese residents can only hope that the lessons learned will prevent similar ecological mistakes in the future.

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