Impact of an environment-friendly rice-production method on the population density of Pelophylax nigromaculatus frogs

Frogs play crucial roles in ecosystems as both predator and prey within food webs. The decline in their populations is attributed, in part, to modern, intensive rice farming practices. In the Tajima region of Hyogo Prefecture, Japan, a subset of farmers has embraced a “white stork friendly farming” (WSFF) method since 2003, which promotes environment-friendly rice production to preserve and restore biodiversity while aiding the reintroduction of the Oriental White Stork (Ciconia boyciana) into the ecosystem. Here, we hypothesize that the WSFF method has a positive impact on the conservation of black-spotted pond frog (Pelophylax nigromaculatus) populations inhabiting paddy fields. To test this hypothesis, we evaluated the influence of the WSFF method on the population density of P. nigromaculatus. Using a line transect method, we identified and quantified individual frogs observed on the paddy field levees in June 2016. Subsequently, we analyzed the effects of rice production using the WSFF method and land-use factors on the frogs’ population density. Our findings indicate that P. nigromaculatus population density increased with the expansion of paddy-field areas managed under the WSFF method within a 100 m radius of the paddy-field center. These results suggest that rice production following the WSFF method has a positive impact on the conservation of this frog species.