Mr. Asada is just one of many growers in Shizuoka, one of Japan's largest wasabi-growing（山葵种植）regions, who must face rising challenges from global warming and the effect of untended forests. Already. these hazards have gradually weakened the centuries-old culture of wasabi in the area and damaged the future of one of the area's most important agricultural products and its tourism business.
Over the last decade, the number of wasabi produced in Shizuoka has dropped by close to 55 percent, according to the Department of Agriculture, Forestry and Fisheries. The wasabi that comes in tubes and packets is actually a mixture of wasabi and horseradish（辣根）—or includes no wasabi at all. These days. almost only expensive restaurants have access to fresh wasabi. giving their customers a chance to experience the unique flavor and traditional culture of wasabi.
Wasabi plants grow up in spring water that flows down from the mountains, helping to improve their flavor and sweetness. Over time. local growers say, the spring water has worsened in quality due to a large number of cypress trees which grow like crazy in the untended forests.
Global warming has upset the balance even further. The delicate wasabi plants, which take more than a year to be full-grown, do best in conditions no higher than about 70 degrees Fahrenheit. In recent years, heat waves in Japan have regularly pushed temperatures into the 90s and even above 100 degrees. causing more stems to rot.
Government researchers and local growers have started to experiment with crossbreeding in an effort to develop better wasabi varieties that will grow strong even in the rising heat. The challenge is that. unlike with other crops such as cucumbers or tomatoes. getting seeds and growing seedlings from wasabi requires advanced technology. Most growers rely on specialized companies to clone seedlings in labs and greenhouses. Crossbreeding new varieties needs difficult pollination（授粉）efforts, and most of all. time.
