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Aso-Kuju NP, Oita
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In 1952, Kyushu University students tending the Asebi mountain hut near Bogatsuru rewrote a song from a Hiroshima mountain club for Kuju. Hikers still sing “Bogatsuru Sanka.”
After livestock declined, spring burning stopped in the late 1960s and shrubs overtook Bogatsuru. In 2000, 150 locals and volunteers restarted it after a 32-year gap; the burns now help keep the marsh open.
Chestnut-eared buntings nest in Bogatsuru’s summer grass. Oita Prefecture identifies the surrounding highlands as the species’ southern breeding limit within the prefecture, making this marsh an important nesting ground.
Each summer, volunteers pull non-native weeds such as fleabane by hand, one plant at a time, to protect Bogatsuru’s native marsh plants, including Japanese iris and Hankaisō.
Bogatsuru spans 53 hectares at roughly 1,200 meters, while nearby Tadewara covers 38 hectares near 1,000 meters. Together, the 2 marshes form a 91-hectare wetland site recognized internationally in 2005.
Bogatsuru formed in a basin ringed by volcanoes including Mimata, Hiji and Taisen; nearby Tadewara sits on a volcanic fan. The twin wetlands share a Ramsar listing, but their landscapes formed differently.
As peat thickens, groundwater has less influence and nutrients decline. That process places Bogatsuru between a groundwater-fed low marsh and a raised bog—the ecological transition captured by “intermediate marsh.”
