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Joshin’etsukogen NP, Niigata / Nagano
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Naeba’s broad, level summit is a volcanic gift: late lava flows made a plateau where roughly 3,000 ponds formed. Sediment studies suggest they began about 7,000 years ago, likely as snowfall increased.
One explanation links 苗場山 (“seedling field”) to ponds resembling rice nurseries. Yet a regional-history study finds the name rare in nearby Akiyama and Sakae records before Edo times, when rice farming there was uncommon.
A core from the summit wetland preserves 12 visible Holocene ash layers. Some mix ash from several volcanoes or were reworked later—so this quiet bog is also a record of eruptions across the region.
Peat builds here at about 1 mm a year, while the soil stays strongly acidic and nutrient-poor. Among the wetland’s specialists is sundew, a tiny plant that catches insects.
The ponds are not identical underwater: a study of Naeba’s pools found that different amounts of suspended organic matter were associated with different dominant species of tiny crustacean plankton.
A Ministry of the Environment ranger found some summit boardwalk planks slightly tilted, likely shifted by moving snow. The paths are there to protect the fragile wetland plants beneath them.
