Environment of the Seto Inkand Sea, Japan related to land and watershed activities

Abstract Enormous amounts of contaminants discharged from land and watershed areas due to human activities have been causing serious marine pollution throughout the natural water-cycling system. Fortunately, serious water and sediment pollution of Japan's coastal zone has been improved in recent years. However, mounting environmental problems are predicted to diversify and expand regionally in the years to come. Therefore, effective environmental preservation and management steps should be systematically taken with a view to protecting the material-cycling system in this integrated ecosystem of land, watershed and coastal zone. For this reason, it is indispensable that each researcher who studies land, watershed, or coastal areas mutually understands environmental problems in each research field. In this paper, the author describes the historical changes in and present state of the environment in the Seto Inland Sea, which is the largest semi-enclosed inland sea in Japan, to better understand the environmental problems of coastal zones related to land and watershed activities.