Effectiveness of Wildlife-Friendly Farming on Aquatic Macroinvertebrate Diversity on Sado Island in Japan

Abstract

Paddy fields are important as alternative wetland habitats for a range of aquatic and semi-aquatic wildlife that once inhabited floodplain habitats. However, depopulation and aging in rural communities have led to the loss of biodiversity across rural areas of Japan. In Japan, wildlife-friendly farming is typically implemented using charismatic wildlife as an icon, and much attention has been given as a means for restoring paddy field biodiversity. Sado Island in central Japan is among the leading areas for such wildlife-friendly farming in terms of the implemented area. Nevertheless, scientific evaluation is largely lacking for the effectiveness of wildlife-friendly farming on paddy field biodiversity. Using four aquatic macroinvertebrate taxa as indicator groups, we surveyed over 300 paddy fields in winter and summer across Sado Island. In winter, although most indicator groups were significantly associated with the percentage of water coverage in paddy fields, winter flooding had limited effects on aquatic macroinvertebrate abundance or richness, because of large variations in water coverage among paddy fields. In contrast, implementing diversion ditches provided additional habitats for aquatic macroinvertebrates that prefer deep-water habitats, resulting in the separation of macroinvertebrate composition between paddy fields and their adjacent ditches in both winter and summer. Furthermore, agrochemical reduction and fallow flooding were effective in enhancing aquatic macroinvertebrate abundance and richness in summer. Overall, diverse practices of wildlife-friendly farming contributed to the enhancement of aquatic macroinvertebrate diversity on Sado Island.KeywordsEnvironmentally friendly farmingPaddy fieldRice agricultureBiodiversityGIAHSEcological restorationBenthic macroinvertebrate