Survey of Impact of the Great East Japan Earthquake on the Natural Environment in Tohoku Coastal Regions

Abstract

The impacts of the Great East Japan Earthquake that occurred on March 11, 2011, to the natural environment in the coastal area were surveyed in April 2012 to March 2016 by Biodiversity Center of Japan, Ministry of the Environment. Sand dunes and coastal forests received direct impacts from the tsunami, while some new hygrophyte communities were generated from buried seeds in the remains of rice paddies. Although natural recoveries of vegetation (e.g., from open water to wet grassland) were observed at some areas, artificial impacts such as reconstruction projects turned wetland plant communities into artificial bare land. Some places (e.g., reclaimed lake) were turned back to original environment by the comparison with the land cover of 100 years before the earthquake. Many shorelines that had receded due to erosion accompanied with the tsunami had made early recovery except for some river mouth bars and pocket beaches. Distribution of seaweed (Phaeophyceae spp.) seemed to have little impacts. On the other hand, seagrass (Zostera spp.), which generally grow on the sediment of sand and silt, had heavy impact because the tsunami swiped the sediment away although many cases of recovery of seagrass beds were observed 4 years after the earthquake. Moreover, fauna and flora survey in key sites and monitoring on pre-surveyed sites of tidal flats, seagrass beds, seaweed beds, and seabird breeding sites have been conducted. According to the series of the surveys, the living organisms were seemed to be adapted to the natural disturbance although some were still in the middle of recovery process. All of the data of these survey results were archived and are disclosed at “Shiokaze Natural Environment Log” .