Radioactive contamination in forested area in Fukushima after the nuclear power station accident in march 2011: Influences of the policy decision not to decontaminate forests on restarting of agriculture and life

The explosions of the nuclear power station at Fukushima in March 2011 released a large number of radioactive nuclides into the surrounding environment. The territory of the Fukushima prefecture is mainly covered by forests (71%). The local communities have traditionally utilized natural resources from forests in their daily lives and agricultural processes for a very long time.

Our intensive monitoring since 2011 at a forested headwater catchment in northern Fukushima have demonstrated that after the drastic redistribution of radiocesium in early years after the accident, the spatial distribution of radiocesium has become stable and most of the radiocesium is accumulated in the surface layer of the soils. As the radiocesium flowing out of the forest through the streams was less than 1% of the total fallout amount in every year, it is clarified that radioactive substances will continue to exist in the forest for many years in the future.

In the heavily contaminated areas, evacuation orders were issued by the national government. The government and local municipalities have operated decontamination processes of the living areas and agricultural fields over the past five years and canceled the evacuation order gradually from the area where the air dose rate fell below the reference value. The policies to prepare the conditions for restarting agriculture have advanced. However, even if evacuation orders are released, the return rate of residents in those areas is around 15%. One of the major reasons was that forests have not decontaminated. The local residents may consider that only decontamination of living areas and farmlands is insufficient for the comprehensive reconstruction of living and agricultural activities. Policy decisions not to decontaminate forests were made at the national level and top down enforcement was proceeded. At this decision making, linkages between forest and agriculture and life were not evaluated as important. This was presumed to be due to the absence of scientists or processes advising this importance based on scientific data. As future challenges, municipalities and residents should understand actual forest pollution levels and implement necessary forest decontamination for area by area. For this challenge, there is a need for scientists to be involved in these bottom-up activities.