Conservation of frog habitats for land consolidation projects in paddy field areas

Abstract

Recently in Japan, land consolidation projects of paddy fields have been carried out considering the environment In such projects, frogs are often selected as conservation target species. To contribute to effective conservation of frog habitats, this paper reviews the ecological characteristics of frogs inhabiting rural areas, the effects of land consolidation on frogs, and available countermeasures to conserve their habitats. Then, future related research areas are discussed. First, 13 domestic species and subspecies are summarized based on their migration characteristics between habitats and breeding sites. Second, four reasons are presented to explain potential causes of decreased frog population after such projects 1 frogs die after the topsoil of paddy fields is peeled, and existing earth agricultural canals are destroyed during construction; 2 concrete canals restrict migration among habitats 3 quantitative and qualitative changes in levees of paddy lots affect their habitats owing to land readjustment and conversion to concrete levees from earth ones; and 4 breeding and overwintering sites disappear due to reformation into well-drained paddy fields. Third, five countermeasures to conserve frog habitats are explained: 1 protecting and moving individuals before construction 2 installing lid structures to prevent individuals from falling into the concrete canals and slopes to enable frogs to escape from the canals 3 creating nature-friendly canals and biotopes to provide suitable inhabiting, breeding, and overwintering sites to frogs; 4 environmental consideration of water management and field management in the paddy fields, such as cultivating with less or no agrochemicals; and 5 dealing with alien species. In future, changes in the consolidation approach, such as the further enlargement of paddy fields and the introduction of smart agricultural technology, are expected to become increasingly common in rural areas. It is necessary to evaluate the impacts of such changes on frog habitats and to consider countermeasures against negative impacts.