On the Niigata Prefecture coast of the Sea of Japan is a wetland called Sakata (spanning 76 ha), which was registered to the Ramsar List of Wetlands of International Importance in 1996. Sakata is shallow, with an average depth of 1 meter. More than 100 species of wild bird can be observed throughout the year at Sakata and close to several thousand swans and ducks migrate here, particularly in the winter. It is also a habitat for precious aquatic plants such as fox nut and mizuaoi (monochoria korsakowii), numbers of which are falling alarmingly throughout the nation.
Not only is Sakata a habitat for this diversity of wildlife, it has also been traditionally used as an agricultural basin, while also serving as a source of carp, eel and edible lotus roots and water caltrops.
In September 2009, about 170 fishing union members and local residents gathered at Sakata to hold a katabushin, which refers to a cooperative clean-up operation that local residents have conducted in Sakata since the Edo period (1603–1867).
Clean-up it is, but it is not about merely picking up trash. It involves, for example, cutting common reeds within the wetland. While reeds adsorb phosphorus and nitrogen that cause water degradation, they proliferate rapidly and when they die, they sink to the lakebed, which is when they cause water degradation. Cut reeds are reused as material for manure.
The clean-up operation also scrapes out dirt that accumulates on the lakebed. This allows water that had stagnated because of the dirt to flow and thereby improve the bed environment. Scraped dirt is used as compost on local fields.
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