Why Has Inokashira Park Pond Turned Matcha Green?
A pond at Inokashira Park, a popular destination in Tokyo's Kichijoji area, has turned a striking matcha-like green, a phenomenon that has become particularly noticeable in 2026 and is believed to be caused by an accumulation of phytoplankton. (News On Japan)
Inokashira Park's pond in Tokyo's Kichijoji area has recently transformed into a vivid matcha green color, a striking phenomenon that has gained attention in 2026. The pond, situated within Inokashira Imperial Gift Park and spanning nearly 42,000 square meters across Musashino and Mitaka cities, exhibits this unusual hue due to an accumulation of phytoplankton.
Professor Shinichi Nakano from Kyoto University's Center for Ecological Research explains that while the change in appearance is visually striking, it does not pose a health risk when observed from a distance. However, the decomposing phytoplankton can release an unpleasant odor, making it advisable to address the issue before it becomes problematic.
The experts suggest that completely draining the pond and reducing the nutrients in the mud, which serve as sustenance for the phytoplankton, would be the most effective solution. While the park has previously carried out such complete pond-draining operations, the process is large-scale and costly. Consequently, local authorities must carefully consider the best approach to managing the issue, ideally draining the pond once a year to maintain its appeal and minimize any potential hazards.
Similar dramatic color changes in water and landscapes can be observed in various locations across Japan and globally, such as Numazu's bluish-white sea due to marine plankton, Yellowstone's Grand Prismatic Spring's spectrum of colors, Peru's Rainbow Mountain's vivid bands of red, green, and yellow, and Shark Bay's blood-red sky and landscape caused by iron oxide.
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