Floating Island Restoration and Reforestation Progressing in Shingu

In Shingu City, on the Pacific coast of Wakayama Prefecture, located south of Osaka in Western Japan, there exists an island of peat floating in a pond. The peat was created by the remains of plants growing abundantly since ancient times. In the forest that has grown up on the island, clusters of rare plants of scientific significance are growing, and the island has been designated a natural monument.

In the past few decades, however, the area surrounding the pond has been developed and turned into residential land. Groundwater has been depleted, while earth and sand have eroded into the pond from the development. Consequently, the pond dried up and the floating island became stranded. The quality of the pond water had also declined due to household wastewater and sewage flowing into the pond, degrading the wetland environment and endangering the forest growing on the island.

Shingu City has been working for some years to solve these problems in cooperation with the national and prefectural governments, and eventually decided to purify the pond water by bringing in water from the Kumano River, a large river running nearby. Full-scale transmission of this water started in in September 2003. Up to 30 liters of river water per second now pours into the pond through pipes set up along a hiking trail through intervening forest.

According to research conducted in March 2004, the result has been a reduction of biological oxygen demand (BOD) from 4.7 recorded before water transmission started to 1.2 after, while turbidity improved dramatically from 20 to 5.3. The pond used to be turbid and muddy, but now small fish are seen swimming around and sphagnum moss is growing prolificly. The wetland and forest are recovering.

The floating island used to rise and fall together with the level of the pond surface. It was moved by strong winds, and swayed when a person stomped hard on its surface. Research has revealed that some areas now functioning as land used to be under water, and that the island is now only partially stranded. Thus it is expected that the island can return to something closer to its former state if the area of open water on the pond expands and the process of recovery continues.




Posted: 2004/07/16 10:08:00 AM
Japanese version