The Steady Decline of Hamanako Lake Clams—Japan's Search for a Circular Economy (May 2001)

The Steady Decline of Hamanako Lake Clams—Japan's Search for a Circular Economy (May 2001)

In May 2001, Lake Hamana's once-abundant clam resources were rapidly declining, severely impacting the local aquatic environment. The primary cause was the disruption of the delicate brackish water ecosystem balance, resulting from a combination of factors: deteriorating water quality since the 1990s, domestic wastewater discharge, red tides, worsening bottom sediment conditions, and years of overfishing. Bivalves are highly sensitive to environmental changes, making the drastic decline in clams a crucial indicator symbolizing the impact on the lake's ecosystem. This period coincided with national policy emphasizing the construction of a circular society, and Lake Hamana's problems gained significant social attention as a concrete example prompting consideration of resource sustainability. Local governments and fishing cooperatives advanced initiatives like water quality improvement, tidal flat restoration, and juvenile shellfish cultivation, prompting discussions on the need
to reexamine the relationship between humans and nature. Yet, the lakeshore in the late 1970s was astonishingly rich: large clams littered the shallow waters near Kanzanji Temple, cherry shells could be gathered along the coast, and natural oysters thrived on the rocky shores at low tide. Near the National Hospital stood pear orchards; the mountain stream at Okuyamadera Temple teemed with stream crabs; and around Lake Sanaru, even residential areas echoed with the chorus of cicadas. It was an era when pollution was becoming a problem, yet it was also a rich time when nature's vitality could be felt as part of the everyday landscape.