麻豆传媒

In recent years, a tidal flat?— a landing zone for migratory birds — in Nagoya has seen massive amounts of plastic waste washed ashore after flowing out of rivers.

The Nagoya City Institute for Environmental Sciences in 2021 started looking into the?Fujimae tidal flat’s plastic waste pollution?and how microplastics might enter the bodies of wildlife and adversely affect?ecosystems.

The tidal flat, situated at the innermost part of the Ise Bay, straddles Nagoya and the village of Tobishima in Aichi Prefecture and is known as a vital stopover for migratory birds such as sandpipers and plovers.

In 1981, Nagoya announced a plan to turn the tidal flat into a landfill as existing garbage disposal sites were running out of space, but it gave up on the idea in 1999 following strong local opposition. The city then declared a state of emergency for garbage disposal, which prompted residents and businesses to work on sorting and reducing waste.

In 2002, the Fujimae tidal flat was registered as a wetland of international importance under the Ramsar Convention and has since then been protected as a wetland hosting diverse wildlife.

One day in mid-May, some 60 volunteers for a beach cleanup saw the tidal flat littered with countless plastic fragments of different colors — red, white and translucent — and various sizes, ranging from ones that can be picked up by hand to those that are difficult to identify unless examined very closely.

Wild birds look for food on a tidal flat in Nagoya during low tide. | CHUNICHI SHIMBUN

“It’s going to be tough if we think about picking up every one of them,” said a 60-year-old man as he gathered the debris. “We wouldn’t be able to leave even after two hours.”

Microplastics are defined as plastic fragments measuring 5 millimeters or less in size. They are formed when big plastic items such as plastic bags and empty fertilizer coating shells flow into the rivers or oceans and break up into small particles, driven by water flow and ultraviolet rays of sunlight.

Kazuhiro Banno, the 75-year-old leader of the cleanup campaign who has more than 20 years of experience cleaning up the Fujimae tidal flat, said, “Compared with the past, we are seeing less of conspicuous household waste, but small pieces of plastic waste has become an issue over the last couple of years.”

In response calls for action on the matter, the Nagoya City Institute for Environmental Sciences has been collecting and sorting items washed up on the tidal flat since 2021 by scooping up its surface every year in an area measuring 15 square centimeters and 1 centimeter?deep.

It found that approximately 10% to 30% of the total mass of the debris, including soil and wood, was plastic. In research done in 2025, the institute collected 2,864 pieces of plastic debris, of which roughly 98% were microplastics.

According to the institute, pieces of trash that drift from rivers and oceans are said to be more likely to gather on tidal flats due to the daily rise and fall of the tide.

The Fujimae tidal flat is located at the mouth of the Shonai River, the Shin River and the Nikko River. As such, waste flowing out of the three rivers tends to accumulate at the tidal flat.

The institute plans to do research on the three rivers as well in order to identify the sources of the plastic waste found in the Fujimae tidal flat, as well as assess how they impact wildlife and the environment.

“I can’t help but think (microplastics affecting the tidal flat) is a microcosm of our daily life, in which we rely on plastics that are low-priced, lightweight and hygienic,” Banno said.

According to Satoshi Chiba, a visiting professor at Yokkaichi University who specializes in coastal marine environmental science and is well-versed in marine debris, if wildlife mistakenly consume plastics, their digestive tract’s?nutrient absorption would become?hampered and they would also suffer from the toxic effects of pollutants adsorbed onto plastics.

In an experiment that involved feeding 3-millimeter-long zooplanktons with 20-micrometer microbeads, both the egg sizes and hatching rate of the zooplanktons were reduced as a result.

Chiba, who analyzed the mud at the Fujimae tidal flat in 2022, also found that?the larger the number of pieces of plastic discovered, the smaller the sizes of microplastics tended to be. He believes plastic waste becomes more fragmented over time.

If planktons and small fish consume microplastics, there is a risk of migratory birds eating them, which would result in a wider spread of the microplastics.

Chiba said no conclusion has yet been reached over the causal relationship between the density of microplastics and its impact on wildlife. Still, he pointed out, “The smaller the particles the easier it is for them to be absorbed into the bodies, meaning they could affect the entire ecosystem.”

He also said it becomes more difficult to collect microplastics if they are more fragmented.

“First and foremost, it is important for society as a whole to seriously take measures not to make plastic items of visible sizes flow out into the sea,” he said.