The Shibayachi wetland harbors a rich variety of marsh plants, typical of lowland mires. It is a rare wetland which remained undestoryed in an urban area. Its isolation from the rest of vegetation helped the preservation of its genuine flora since old times. For this reason, the government designated this wetland a national natural treasure in September 1936.
As many as 73 species of marsh plants such as nohanashobu (iris ensata var. spontanea) and sundew are present and many water birds such as waterhens, little grebes and Indian spot-billed duck visit here. Looking into the water, we find another world with small insects such as whirligig beetles, diving beetles and dragonfly nymphs.
Dragonfly nymphs spend a couple of years under the water before emergence. Male and Female dragonflies mate while flying in the air and female dragonflies lay eggs in the water. They are born in water and, after flying high in autumn, go back dead to the mother water in winter. They are not the only ones to repeat the perennial cycle of life and death in the Shibayachi wetland.