Every spring, there is an illness that torments many Japanese people. It is a pollen allergy known in Japan as ‘kafunsho’. As roughly 40% of the population report suffering from pollen allergies, ‘kafunsho’ is also called a ‘national disease’. The pollen allergies experienced by Japanese people are mainly caused by pollen from plants such as Japanese cedar and cypress. They primarily cause symptoms like sneezing, runny nose, and nasal congestion.

On the 5th, the Asahi Shimbun reported that the surge in pollen allergy patients in Japan has occurred over the past 60 years, with the first patient caused by cedar pollen reported in 1964. Since then, cases due to cedar pollen have increased rapidly; according to a survey of otolaryngologists nationwide and their families, the share rose from about 20% of the total population in 1998 to about 30% in 2008 and about 40% in 2019. The prevalence is so high that pollen forecast services have even emerged.

This rise to the level of a national disease is largely due to changes in forests, which cover 70% of Japan’s land. In Japan’s artificial forests totaling about 10 million㏊ (hectares; 1 hectare is 10,000㎡), Japanese cedar accounts for 44%. Cypress is next at 25%.

The high proportion of cedar and cypress in Japan’s artificial forests stems from the period of rapid economic growth, when fast-growing conifers were planted in large numbers instead of broadleaf trees for use as timber. However, as cheap timber was imported from overseas and domestic forestry stagnated, most of the cedars planted across Japan were left unharvested.

Japanese cedar begins to release large amounts of pollen once it is more than 20 years old, and Asahi reported that Japan’s artificial forests are now filled with cedars that shed abundant pollen. Abumi Michiko, head of the Tokyo Metropolitan Government’s Forestry Division, told Asahi, “Most of the trees have never been felled since they were planted after the war.”

Of course, the Japanese government is not simply standing by. It is implementing measures such as logging old cedars while replanting with low-pollen varieties. The goal is to reduce by 20% the area of cedar stands over 20 years old that produce heavy pollen. The government plans to expand the annual logging area from about 50,000㏊ to 70,000㏊.

However, given that cedar accounts for 44% of the 10 million㏊ of artificial forests, mere tens of thousands㏊ per year is far too little to achieve the goal of reducing pollen allergies. In particular, many artificial forests are small private holdings under 5㏊, and even when the national or local governments try to proceed with cedar logging, many owners do not cooperate. Although logging cedar imposes no financial burden on ownersand they can even earn income by selling the timberthe area of private forests actually being felled amounts to only 40~60㏊ per year.

Abumi said to Asahi, “I hope plantation owners will make greater use of the (logging) system,” adding, “I would like consumers to use more wood in daily life so that more trees can be felled.”