Effects of rice-field abandonment rates on bird communities in mixed farmland–woodland landscapes in Japan

Abstract

Abstract Farmland abandonment can be a significant driver of biodiversity change in many parts of the world. Knowledge of the ecological impact of farmland abandonment at the landscape scale is particularly limited in Asia. We investigated how rice-field abandonment impacts bird diversity (i.e., species richness and composition) during the breeding and wintering seasons. Birds were surveyed in 31 grids (1\xa0×\xa01\xa0km) in rice ecosystems in central Japan, 16 of which were dominated by farmland while the others were surrounded by woodland. In each landscape type, survey grids were selected to ensure a broad range of abandonment rates, from fully cultivated to largely abandoned sites. Multi-species occupancy models showed that occupancy probabilities were associated with linear and quadratic terms of the abandonment rate, resulting in the highest predicted community-level occupancies and species richness at moderate abandonment rates (51.5–71%, depending on the season and surrounding landscapes, with the highest percentage in woodland landscapes in winter). Community composition was most associated with surrounding landscapes (i.e., woodland or farmland), followed by the abandonment rate. These results indicate the importance of habitat heterogeneity, related to moderate levels of farmland abandonment, in enhancing bird diversity in both farmland and woodland landscapes. Our findings illustrate the necessity for quantitative measures of farmland abandonment at landscape scales for understanding their nonlinear effects on farmland biodiversity. We suggest that agri-environmental schemes should consider the benefits of enhancing farmland mosaics at landscape scales, especially for small-scale farming in areas where farmland abandonment is increasing.