What does WWII have to do with Japan’s worsening allergy crisis?

It was the best time. It was the worst time.

Millions of people in Japan celebrate the arrival of spring every year with their delicate cherry blossoms. But the change of season also brings many miserable months of incessant sneezing and nasal congestion.

The hay fever or pollen allergy It has such an impact on Japan that Prime Minister Fumio Kishida in April described it as “a social problem” and instructed his ministers to seek an answer.

Taro Yamada, a parliamentarian from the ruling party, recently declared: “Pollen allergy would be the national disease.”

It is enough to compare Japan with other countries to see the magnitude of the problem.

In the United States, about 8% of the population suffers from hay fever. In other countries between 10 and 30%.

In Japan, on the other hand, hay fever or “kafunsho” (pollen disease in Japanese) affects 42.5% of the populationaccording to a 2019 study by Japan’s Ministry of the Environment.

The percentage, double what it was 20 years ago, currently equates to more than 50 million people.

And the Japan Forestry Agency estimated that pollen allergy causes economic losses of at least $2.2 billion a year, including medical bills and reduced worker productivity.

Why is hay fever so widespread in the Asian country?

The answer lies largely in Japan’s forests and in a story that began more than 70 years ago.

cedars and cypresses

Allergic rhinitis or hay fever is a disease in which the nasal mucosa becomes inflamed and irritated.

The term “hay fever” comes from the 19th century, when the smell of hay was thought to have an irritating effect. But then it was discovered that the disease had nothing to do with fever or hay, but with an allergy to pollen.

Symptoms include sneezing, itchy nose, stuffy nose, runny nose, and watery eyes.

Pollen grains from many plants cause allergic reactions. But in Japan, the problem mainly arises in the forests of two tree species: cedars and cypresses.

This is shown by the same study by the Ministry of the Environment from 2019 38.8% of the Japanese have an allergy to Japanese cedar pollen (Japanese cryptomery), Japan’s national tree known locally as “sugi”.

And 25% of the population suffers from an allergy to the pollen of the Japanese cypress or hinoki (Chamaecyparis obtusa).

People with these allergies may have never seen a cedar or cypress tree before.

The clouds of pollen coming from the woods move with the wind over great distances.

Both Japanese cedar and cypress are native trees to the country and have been part of the landscape for hundreds of years.

That they ultimately contributed to a “national disease” is due to the policies adopted after World War II.

The “Herculean” task of reconstruction

“During World War II, Japan’s forests were cut down and destroyed,” Iwao Uehara, a professor in Tokyo University of Agriculture’s Department of Forestry, told BBC Mundo.

Due to the scarcity of wood after the war, large quantities of cedars and cypresses were planted, because they grow relatively fast, with a straight trunk”.

David Fedman, a historian at the University of California-Irvine, is a specialist in the environmental history of Japan and author of the book “Seeds of Control: Japan’s Forestry Empire in Colonial Korea.”

“One of the most pressing material needs immediately after the war was material for urban reconstruction in Japan,” Fedman told BBC Mundo.

“It is worth remembering here the incendiary bombing campaign that destroyed Japan’s largely wooden buildings in the closing months of World War II.”

“Therefore, the occupation authorities facing a mammoth task of urban reconstruction, as well as a serious shortage of timber and forest resources as a result of Japan’s mobilization for total war.”

The occupation of Japan by the victorious Allies of the war lasted until 1952. In the following years, cedar plantations expanded.

In some cases, several natural forests have even been cleared to replace cedar monocultures, explains Professor Uehara.

“In this way, cedar and cypress plantations grew throughout the country and were carried out on a large scale, even in mountainous areas that were not suitable for these species.”

“Japanese cedar today makes up 45% of planted forests in Japan, and cypress trees 25%added Uehara.

Individual actions were added to state policy.

“People also believed that planting cedars and cypresses would benefit Japan. There was even a song encouraging people to plant cedar and cypress trees.”

non-viable plantations

The vast plantations of cedar and cypress trees became a bad thing in the following decades.

“Cultivation and maintenance of cedar plantations is a labour-intensive task. In the 1950s and early 1960s, there was an abundance of cheap labor, so widespread cedar planting made sense,” Fedman said.

Changes in other industrial and agricultural sectors in the late 1960s and 1970s made cedar an increasingly less viable forest businesshe added.

Changes in the lumber market had serious consequences for cedar lumber.

“I explain them in detail at the end of my book ‘Seeds of Control’. The bottom line is that the economy of domestic logging has become prohibitively expensive. Cheap gaizai (“wood from abroad”) was increasingly importedthereby crippling a significant number of domestic logging activities.”

The lack of exploitation of the local timber caused the cedar forests to become denser and the trees taller, exacerbating the pollen cloud problem.

It is estimated that cedar forests currently cover 12% of Japan’s territory.

Not just the woods

The Japanese Ministry of the Environment estimated in early spring that the amount of circulating cedar pollen by 2023 would be the highest in 10 years.

For Professor Uehara, however, there’s something we shouldn’t forget: cedar and cypress forests aren’t the only “culprits” of Japan’s hay fever crisis.

Other factors exacerbate the pollen allergy problem and have a global impact.

One of them is the pollution in cities.

For example, a study in Switzerland found that some pollutants bind to pollen particles, increasing the allergic response.

And other pollutants can damage the surface of the pollen causing it to break into small fragments.

Climate change also affects the pollen seasonwhich not only starts earlier, but also lasts longer.

There is some evidence that plants produce more pollen and faster when the temperature is higher.

A study this year in the United States found that between 1990 and 2018, the length of the pollen season in North America increased by at least 20 days and the concentration of pollen in the air increased by 21%. According to the authors, this is largely due to global warming.

A lesson for the world

Prime Minister Fumio Kishida warned that Japan’s hay fever crisis “will not be solved overnight and will require sustained efforts”.

A panel of ministers must propose concrete measures in June.

The government has already identified some actions, according to local press: cutting down cedar forests and replacing them with varieties of that species that produce less pollen, using artificial intelligence to make warnings about pollen levels more accurate, and improving medical treatments.

For Professor Uehara, Japan’s post-war hay fever and forest crisis holds a profound and global lesson: Destroying biodiversity can have unforeseen consequences decades later.

“The biggest problem is the artificial planting of a tree species. The main measure should be to promote mixed forests of cedar and other species,” he told BBC Mundo.

“The richness of biodiversity and the hay crisis are inversely related.”

Uehara recalled a line from a “famous seventh-century Japanese volume of poetry called Manyoshu: ‘Pollen flies in the spring, spring has come.'”

“So this pollen problem has been around for 1,400 years!”

“In my opinion, the most basic response to the hay fever problem is to be in harmony with nature.”