Japan's Postwar Reforestation Bet Now Drives a National Hay Fever Crisis

Postwar Japan stripped its mountains for fuel, then rebuilt them by planting fast-growing sugi (Japanese cedar) and hinoki (Japanese cypress) across roughly 10 million hectares — a fifth of the country. Seventy years on, those monoculture plantations have matured past the 30-year mark and now blanket cities in lightweight pollen each spring. Around 43% of Japanese now suffer moderate-to-severe hay fever, far above UK and US rates, with peak-season economic losses estimated at $1.6bn per day from sick leave and reduced spending.

In 2023 the government declared allergies a national social problem and set a target of cutting pollen 50% within 30 years, starting with a 20% reduction in sugi plantations over a decade. Roughly 980,000 hectares have been designated for logging and replanting, some with low-pollen sugi cultivars and some with broadleaf species. Local pilots in Kobe, Nishiawakura and Gunma are converting plantations back to mixed forests, wetlands and meadows, with monitoring already showing returning wildlife.

The scale of the task is daunting: Japan is 68% forested, a third of that monoculture, and simply felling trees risks landslides and undermines climate targets. Even if the 20% goal is met, 80% of the problem plantations remain — meaning relief for allergy sufferers is, at best, decades away.