Bayer and neonicotinoids in Japan

Ryo Futahashi.
German pesticide manufacturer Bayer attempts to discredit rigorous peer-reviewed study showing its products caused a Japan fishery to collapse.


I still remember the only dragonfly I saw in the rice-fields near the Arakawa River in Saitama Prefecture, Japan in 2019. It was large, with a rust-brown body and it paused for a moment, balancing on the air, before darting away.

I had observed the rice cultivation there all year, from when the pesticides were sprayed on the crop until the harvest, and dragonflies and other insects were conspicuous by their absence.

In Japan, as in rice-fields worldwide, spraying is usually with broad-spectrum neonicotinoid pesticides or else fipronil, both developed by German chemical company Bayer. Neonicotinoids are the subject of a ban for outdoor use in the European Union and fipronil, which is now marketed by another company, has been banned in China.

Dead zone

The May 2019 newsletter of the Saitama Ecosystem Conservation Society describes how, before the introduction of these chemicals in the 1990s, numberless brilliant red akiakane or autumn darter dragonflies could be seen around rice fields in the fall.

These dragonflies, which have their larval nymph stage in the water of rice paddy fields, are an eye-catching indicator species for other water insects in the ricefield ecosystem. Some are considered by farmers as pests, and the powerful insecticides from Bayer offered a solution. But after their use many complained that the rice fields had become a dead zone except for the rice plants.

Experiments by Japanese dragonfly expert Tetsuyuki Ueda of Ishikawa Prefectural University showed how the pesticides reduced the number of surviving dragonfly nymphs to a small fraction, and that the chemicals persist for years in the soil of rice paddy fields.

In addition, the poison was getting into the rivers and accumulating in Lake Shinji in Shimane Prefecture in the west of the main Japanese island of Honshu. Lake Shinji is surrounded by rice paddy fields.

A team of Japanese scientists led by Dr Masumi Yamamuro published a study in the prestigious peer-reviewed journal Science in November 2019 showing how the important fishery there collapsed after the introduction of Bayer’s pesticides, and has not recovered. 

Nearly 300 tons of smelt was caught annually in the late 1980s, but since 1993 - when neonicotinoids were introduced in the lake watershed - the smelt catch collapsed to zero and has stayed there.

The study explored different possible reasons for the collapse and clearly demonstrated that it was due to several types of neonicotinoid poison that had killed the insects the fish feed on.


While Japan is a wealthy country with other food supplies, Yamamuro’s team said that the same thing was almost certainly happening in rice farming countries worldwide. This conclusion has chilling implications for poorer countries where Bayer does business, and the loss of a fishery can be literally life or death for local people.

Since the study was published, Bayer has completely dismissed its findings, as reported by Douglas Main writing for National Geographic.

Carlota Gomez de la Hoz, Bayer’s head of issues communications, repeated this dismissal in a statement sent to The Ecologist by email. “We would like to emphasize that the strong conclusions made in the publication are clearly not supported, as demonstrated by the observed increase in fish and eel populations during years with higher neonicotinoid sales (and assumed use).”

Gomez de la Hoz continued: “There is a consensus in the scientific community that understanding changes and causation in these environments requires considerably more intensive investigation than this publication offers. Neonicotinoid products...are safe when used according to instructions, and nothing in any study, including this one, has changed that.”

However, Yamamuro, who has a PhD from the University of Tokyo, explained by email that the strict peer review process for Science took seven months, with the journal sending the study to two anonymous reviewers, whose criticisms had to be answered before the journal would publish.


In a world that has become used to terms like “fake news” and “alternative facts”, peer-reviewed results of studies by reputed scientists must still be considered as truth when multiple reports give the same result.

The repeated claim by Bayer that the methods and conclusions of the Lake Shinji study are wrong may therefore be considered as part of a continuing disinformation campaign against scientists that criticise the company, with the sole aim of maximizing profits for shareholders. 

The disinformation technique employed against Yamamuro is similar to campaigns by climate change denialists, where single anomalous events such as a cold period in winter are cherry-picked to falsely state that a long-term global heating trend does not exist.

Bayer’s statement that in some years fish populations increased does not change the fact confirmed by the peer-review process that overall, the smelt fishery collapsed since neonicotinoids were introduced and has not recovered.

The implications are ominous. The scrupulous study by Yamamuro’s team has brought a terrifying new word into focus that is likely to be attached by future generations to Bayer in much the same way as climate change denial has been to the fossil fuel industry. The word is “trophic cascade”, describing how the loss of the insects at the bottom of the food chain leads inevitably to the collapse of everything dependent on it. 

However, Bayer has so far felt safe to ignore this hard reality, perhaps thinking that there is no economic impact, and there is no sign the company is taking the issue seriously.

On the contrary, Bayer appealed to the European Court of Justice against the European Union’s ban on all outdoor use of neonicotinoids, losing in May 2018 when the court ruled that it was an appropriate application of the precautionary principle. Peer-reviewed studies linked the chemicals to declining bee populations. These were bitterly disputed by Bayer. 

Historical parallel

In Japan, the chemicals remain in use, and Jun Hoshikawa of Act Beyond Trust, an NGO that campaigns against systemic pesticides, said that Japan has weak laws because Bayer and other pesticide manufacturers have a strong influence on the regulatory process.

Yamamuro’s team showed the effects of this combined lobbying and sales effort clearly, with sales of neonicotinoids increasing four-fold from 2000 to 2016 in Shimane Prefecture where Lake Shinji is located. The study also points to a cumulative effect of different kinds of neonicotinoid making them even more dangerous.

To the south of Lake Shinji on the west coast of the Japanese island of Kyushu, the town of Minamata and the chemical company Chisso Corporation became synonymous with horrific human consequences of a trophic cascade due to denial of chemical pollution.

For decades from the 1930s, organic mercury was discharged by Chisso into the ocean, contaminating the fish. A series of terrible birth deformities due to local people eating the fish was memorably recorded by the photographer W. Eugene Smith.

Scientific studies showed a likely link with Chisso, but the company disputed the link and refused to voluntarily stop the discharge. Eventually, under international pressure due to Smith’s photographs, the Japanese government enacted strict pollution control laws in the 1970s and the pollution, and the deformities, ended.


Is Bayer’s published Corporate Social Responsibility (CSR) policy simply in place to distract from the business of making money from ecosystem-wide devastation? The evidence points in this direction.

Bayer spokesperson Gomez de la Hoz said that Bayer’s CSR sets high standards: “Raising the bar in transparency, sustainability and engagement with all stakeholders including the scientific community with integrity and respect.” The CSR section of the company’s website also talks about their commitment to the environment, stating: “In the course of our business activities, we aim to use natural resources responsibly and respect biodiversity”.

However, the reality is one of relentlessly trying to undermine and discredit any reports, including peer-reviewed studies, that show the company’s products harm the environment.

The world depends on insects, and multiple studies show that insect populations are disappearing. Long-term studies are crucial to understanding this because insects can reproduce rapidly in response to favorable conditions, but an emerging consensus is that a mass extinction event is underway and that broad-spectrum systemic pesticides including neonicotinoids are a major cause.

University of California professor Art Shapiro, who has carried out one of the longest continuous studies of butterflies in California over 47 years, is reported as saying that a long-term decline is occurring and pinpoints a major decline that occurred in the 1990s at the same time as neonicotinoid pesticides came into widespread use. This is the same as Yamamuro’s team found in Lake Shinji and dragonfly experts have found elsewhere in Japan.

Trophic cascade

Gomez de la Hoz said: “We do acknowledge that a decline of insect abundance is currently being reported from various parts of the world.”

However, the statement also makes the claims that “there is no evidence which would point to pesticides as a key factor” and “there is no evidence of a causal link between the decline of insects and the use of neonicotinoids in agriculture.” 

I believe this is a misleading statement given the increasing number of conscientious peer-reviewed studies, such as the one by Yamamuro’s team, which show the opposite. 

Meanwhile, in a sign that a trophic cascade is indeed underway across Japan, another peer-reviewed study by Satoe Kasahara and Kazuo Koyama published in the journal Ornithological Science in 2010 shows that birds using rice fields suffered a long-term decline in numbers from 1996 to 2009.

They say that changes in cultivation methods in rice fields are a likely factor, which points to the introduction of neonicotinoids that began around 1993.


On the island of Kyushu to the south of the toxic waste site that Lake Shinji has become, protected from the chemical companies by the laws related to Aso-Kuju National Park, I learned about rice farming without pesticides.

The Kuju Home Village Nature School (Kuju Furusato Shizen Gakko), is a nature center in a protected area high in the mountains of central Kyushu which maintains traditional rice farming methods to pass them to future generations.

Walking around the grass at the edge of the rice paddy, startled frogs jump into the water. According to Hideyuki Abe of the center, eight species of dragonfly were observed in 2019 including the iconic autumn darter. The center maintains its rice field in the rhythm of the seasons as people have for two thousand years in Japan, patiently educating children and the public about what they have lost.

The red dragonflies return in the autumn, a brilliant signal that all is well with the ecosystem and the aquatic insects that form the basis of the food chain and fisheries in surrounding rivers and lakes.

Will the Japanese people wake up from the hypnotism of corporate disinformation and spin to realize what has happened and demand action, allowing the dragonflies to return to the rest of Japan?

This Author

Phil Carter is a freelance environmental journalist based in Saitama, Japan. 

Image: Autumn darter dragonfly, Sympetrum frequens. Ryo Futahashi.

More from this author