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Aso-Kuju NP, Oita
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A local tale gives Tadewara a peppery twist: Asahi Chōja supposedly loved aotade, or willow smartweed, said to have grown here. A local guide described its bite and suggested it with somen noodles.
About 6,300 years ago, volcanic ash and rock debris dammed the Shiramizu River, helping form the basin beneath Tadewara. Today, mountain springs keep the marsh supplied with water.
The Ramsar listing recognizes a rare or representative wetland type—not a huge waterbird flock. It pairs Tadewara’s 38 hectares with nearby Bogatsuru’s 53 hectares as one 91-hectare site.
Takahaya minnows live in Tadewara’s spring-fed water, even though almost no creatures thrive in nearby Shiramizu River. Sulfur from Mount Io makes the river highly acidic; the marsh has a different water source.
After the spring burn, Tadewara turns black—then yellow violets flower across the charred ground. The carefully timed fires clear old growth and help keep the grassland from turning into woodland.
The spring burn takes autumn preparation: local workers cut a firebreak about 10 metres wide around the marsh, let the grass dry for roughly 2 weeks, then burn that barrier to help control the main fire.
Burning once helped maintain grass for grazing and livestock feed. As fewer farms needed the grass, local and company volunteers continued the tradition to protect Tadewara’s open landscape and wetland habitat.
The vivid blue globe thistle, higotai, looks like one round flower, but its head is packed with many tiny blooms. The Ministry of the Environment links the plant’s continental origins to Japan’s Ice Age land connection.
In early August, tiny mizuotogiri flowers open at around 3 p.m. and last only until sunset. Their small size makes this brief afternoon display an easy one to overlook.
Team Tadewara began in 2015 after local elementary pupils said they wanted to protect the marsh. Its young members help plan activities, including children’s guiding and camera surveys of wildlife.
Near the marsh entrance is a statue of Heiji, a female Akita who became a self-appointed guide dog in the Kuju mountains. She accompanied hikers for 14 years and remains a local favorite.
Tadewara’s conservation work includes removing invasive cutleaf coneflower, or ōhanngonsō, which can spread densely and crowd out native wetland plants. Local groups and volunteers help tackle the intruder.
