A decision made 70 years ago to plant vast areas of Japan with just two species of trees is now backfired with pollen clouds that are causing allergies in residents, writes the British broadcaster BBC.
In February, a video went viral showing huge, smoke-like clouds billowing from Japan’s evergreen forests. It wasn’t smoke, but pollen, and the video was also a warning to the country’s residents that it’s time to stock up on face masks and allergy meds. Every spring, the streets of Japan are filled with generations of people wearing masks, the main cause of which is pollen-induced hay fever. Hay fever, or allergic rhinitis, has become a national crisis in Japan, with an estimated 43% of the population experiencing moderate to severe symptoms. By comparison, in the UK it is 26% and in the US 12-18% of the population.
In addition to discomfort, these allergies can cause insomnia, reduced concentration, and sufferers are more likely to experience other problems, such as asthma and food allergies. At the peak of the Japanese hay fever season, the economic impact, both through illness and reduced consumption, is estimated at 1.6 billion dollars per day.
The cause of allergies has little to do with poor general health or pollution, and it has nothing to do with the environment in its natural state.
The cause of hay fever is a decision made by national leaders more than 70 years ago.
During World War II, the lack of oil and gas forced the country to turn to its most abundant natural resource – forests – to heat homes and keep industrial operations running. As a result, natural forests were cut down, and the mountains around the major cities of Tokyo, Osaka, and Kobe were completely stripped of forest cover. Noriko Sato, a professor and forestry researcher at Kyushu University, said that after World War II, mountains in many regions were left bare, causing various disasters – mountains without tree cover increase the possibility of landslides and floods. Consequently, afforestation was carried out to prevent soil erosion.
In an effort to achieve rapid forest growth, the government chose to plant only two fast-growing native evergreen tree species to quickly regenerate the forests and provide timber for future needs. Therefore, Japanese cedars and Japanese cypresses were planted over large areas. Today, plantations of these trees cover about 10 million hectares, or about a fifth of Japan’s land area. The problem is that cedars and cypresses produce a lot of light pollen that reaches cities. It is the pollen, which usually spreads from monoculture plantations at the same time, that causes most seasonal allergies. The problem becomes even greater when the trees are over 30 years old and mature, which is the case for most trees planted in plantations from the last century.
Sato pointed out that pollen allergies have become a health problem throughout Japan and that the issue needs to be addressed urgently. In 2023, Japan declared allergies a national problem, and the government came up with an ambitious plan to reduce pollen levels by 50% over the next 30 years. The first step would be to reduce the area planted with cedar trees by 20%. However, changing the forests that cover 2% of the country is a major task, and simply cutting down the forest will not be enough –
new trees must also be planted to prevent soil erosion and not jeopardize Japan’s climate goals.
Walking through the cedar and cypress plantations is strange. All the trees are the same height, and the forest is almost devoid of birds and insects. The ground is covered with needles, and there is little light or sound. It is a stark contrast to Japan’s natural forests, which are saturated with life. With more tree species in the forest, the diversity of species is also greater.
Given that monoculture forests cause major problems, it is understandable why Japan is trying to replace them with something else. However, this is a challenging task, as the country is heavily forested – with 68% of its land covered by forests, Japan is one of the countries in the world with the highest percentage of forested land. About a third of this is made up of Japanese cedars and cypresses.
Even before the government’s decision in 2023, local activists and non-profit organizations had begun converting plantation forests, and in some places the benefits are already visible. Similar projects are currently being rolled out elsewhere in Japan. One of them involves restoring wetlands and grasslands in Hotani, Osaka. For example, the plan is to convert 10,000 hectares of plantation forest into grassland and mixed deciduous forests. The Japanese government has also been involved, including by marking plantation forests for logging.
When cedar and cypress plantations were planted in the 1950s and 1960s, they were not intended to remain there forever.
At the time, it was assumed that the plantations would be gradually cut down and replanted, as had happened before World War II. In the late 1960s and 1970s, Japan’s economy boomed, its big cities began to expand, and it turned out that importing wood from other countries, such as Malaysia and Indonesia, was cheaper. In 2011, Japan set a goal of relying less on wood imports and using more local resources. The use of local wood increased from 26% in 2010 to almost 42% in 2020.
Before the 1960s, Japan did not have a word for hay fever. The first case of an allergy to cedar pollen was identified in 1963, and according to researchers, it was new to the country. Now, there are hopes that a return to more diverse forests will also make it easier to breathe in the spring.
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