Protecting the Corals
The sea outside Tosashimizu is home to more than 100 species of corals, a level of diversity that is rare this far north. The corals can thrive here because the Kuroshio (Japan Current), which flows northward along the Pacific coast of Japan, brings in warm, clear, and oxygen-rich water from the south. A notable example of the life-forms near Tosashimizu is a giant cluster of shikorosango coral (Pavona decussata) in Minokoshi Bay. Almost 50 meters long, this coral colony ranks among the most impressive in the region. But while the local climate is favorable for the corals, they also face a variety of threats.
In September 2001, extremely heavy rain caused severe landslides in southwestern Kochi Prefecture, including parts of Tosashimizu. Many of these landslides reached the sea, disrupting the marine ecosystem and destroying corals. Studies conducted after the disaster showed that forests left unattended are more susceptible to landslides than those where proper maintenance work is carried out. The forest around Tosashimizu is now being thinned regularly to increase its resilience. Local residents also clean the sea and remove excess mud to give the marine life room to breathe.