More than 40% of Japan’s population suffers from hay fever, prompting the government to replace pollen heavy forests with low pollen tree varieties as climate change lengthens the annual allergy season.
Japan is turning to low and no pollen tree varieties as it seeks to tackle a nationwide hay fever crisis linked largely to two species planted extensively after the Second World War.
More than 40% of Japan’s population now suffers from hay fever, locally known as kafunsho according to a report by Mongabay. The condition causes symptoms including sneezing, runny noses, itchy eyes and throat irritation, with symptoms typically intensifying during the spring pollen season.
Two tree species sugi (Cryptomeria japonica) commonly known as Japanese cedar, and hinoki (Chamaecyparis obtusa) or Japanese cypress are considered the main sources of the pollen driving the problem.
Post-war forests fuel allergy burden
Japan extensive plantations of sugi and hinoki were established largely after the Second World War when the country needed large quantities of timber to rebuild homes and infrastructure.
Forests now cover about 70% of Japan land area, with approximately 41% consisting of planted forests. Sugi accounts for around 40% of planted forests, while hinoki represents another 25%.
As a result, roughly two thirds of Japan’s cultivated forests are dominated by species that produce allergenic pollen.
Climate change is adding to the problem. Rising temperatures have caused sugi trees to release pollen earlier, contributing to longer and potentially more intense pollen seasons.
Government targets 20% reduction in sugi forests
In response the Japanese government announced a plan in 2023 to cut down 20% of the sugi trees planted across approximately 4.3 million hectares of forest by 2033.
Most of Japan’s planted sugi trees are now more than 20 years old and have reached an age at which they can be harvested for timber.
Makoto Nakamura, assistant director of the wood industry division at Japan’s Ministry of Agriculture, Forestry and Fisheries, said trees would be removed as they become suitable for use as lumber.
Trees harvested in mountainous areas or deep inside forests are expected to be replaced with locally appropriate species. Trees located closer to roads and timber processing facilities will instead be replaced with newer sugi varieties that produce little or no pollen.
More than 30 low pollen varieties developed
Japanese researchers have developed more than 30 sugi strains designed to produce very little or no pollen.
Toyama prefecture on Japan’s west coast has already planted around 100,000 low pollen saplings in a single year, demonstrating the potential for large scale replacement.
However, expanding the programme nationwide presents significant challenges. Japan’s forestry sector is facing severe labour shortages, making it difficult to harvest existing plantations and establish replacement forests on the scale required.
Timber demand poses another challenge
Japan also faces a declining domestic home construction industry creating uncertainty over demand for the timber generated through the large scale removal of mature sugi trees.
This leaves authorities facing a dual challenge reducing the pollen burden without creating an oversupply of timber that the domestic market cannot absorb.
The Japanese government strategy therefore combines forest management, development of low pollen tree varieties and efforts to find new uses and markets for timber.
The programme reflects how an environmental and public health problem rooted in decades of forest policy is now being addressed through changes in both forestry practices and tree breeding, while climate change adds further pressure by altering the timing and severity of pollen seasons.