Japan faces a persistent health challenge tied directly to its forests. More than 40 percent of the population experiences hay fever, known locally as kafunsho, with symptoms that often begin in January and extend through early May. The issue stems from trees planted decades ago to meet urgent housing needs after World War II.
Postwar Planting Created the Current Problem
After the war, Japan needed millions of new homes. Officials promoted fast-growing sugi and hinoki trees across the country to supply timber quickly. These species now dominate planted forests. Sugi makes up about 40 percent of cultivated areas, while hinoki accounts for another 25 percent. Together they represent two-thirds of Japan’s managed woodlands. Forests overall cover roughly 70 percent of the nation, with 41 percent consisting of planted stands.
Daily Life Disrupted for Millions
Mariko Aoki, a secretary at Japan’s National Diet, described the seasonal toll. Her symptoms start with an itchy nose right after the New Year. They intensify in March with sneezing, a runny nose, and irritated eyes and throat. The discomfort continues until shortly before Golden Week in late April and early May. Rates of kafunsho in Japan run nearly double those reported in the United States.
Warming Extends the Pollen Season
Rising temperatures have shifted the timing of pollen release. Sugi trees now begin producing pollen earlier in the year than in previous decades. This change lengthens the overall allergy season and increases its intensity for many residents. The combination of widespread planting and changing climate has turned a once-limited issue into a nationwide concern.
Government Plan Focuses on Replacement
In 2023 officials announced a targeted response. The strategy calls for removing 20 percent of existing sugi trees and shifting future plantings toward varieties that produce little or no pollen. The approach aims to reduce airborne allergens while maintaining forest cover and timber resources. Implementation will involve both public lands and coordination with private forest owners. Progress will depend on steady funding and long-term commitment across multiple planting cycles. The effort reflects a practical attempt to address a health burden rooted in earlier policy choices. Many residents and visitors will watch how quickly the new approach alters spring conditions across the country.
