Conservation Values of Abandoned Farmland for Birds: a Functional Group Approach

Abandoned farmland area has been expanding globally for decades. Studies showed that conservation value of abandoned farmland has differed among studies and regions, and thus is difficult to predict. However, predicting the effects of farmland abandonment on biodiversity remains vital to the development of appropriate conservation strategies. Here, we compared the species-, community-, and functional group-level habitat suitability of abandoned farmland for birds by comparison with active farmland (pasture, cropland, and rice paddy) and natural wetland on Hokkaido, Japan, over a study area of 400 km × 500 km. Results differed markedly between functional groups. The abundance and species richness of grassland species in abandoned farmland were higher than that in active farmland, and comparable to that in wetland. In contrast, abundance and richness of bare-ground species was highest in active farmland. For most species, interactive effects between climate variables and abandoned farmland were not significant, suggesting a consistent habitat suitability of abandoned farmland irrespective of varied climatic conditions. Our results suggest that abandoned farmland plays an important role as habitat for grassland and forest species at large scales; farmland abandonment provides a valuable alternative habitat for species whose primary habitats have been lost to agricultural expansion. Especially, abandoned farmland in warmer areas in Hokkaido would represent a potential mitigation to the negative effects of wetland loss. A functional group approach synthesizes varied species-level responses and allows for a comprehensive understanding of the habitat suitability of abandoned farmland. Adopting this approach will contribute to establishing appropriate conservation strategies.