Assessing the landscape-dependent restoration potential of abandoned farmland using a hierarchical model of bird communities

Expansion and intensification of agriculture have led to an immense decrease in biodiversity. However, the area of abandoned farmland has been increasing globally in recent years and is expected to provide novel habitats for various organisms. Despite the promising potential for biodiversity conservation in agricultural landscapes, few studies have compared biodiversity among multiple land use types, including abandoned farmland. We examined the effects of major land use types (wetland, grassland, forest, farmland, abandoned farmland) and the surrounding landscape openness (proportion of wetland/grassland in the surrounding area) on the abundance and species richness of bird communities and four functional groups (wetland, grassland, farmland, and forest species) in the agricultural landscape of central Hokkaido in northern Japan. The abundance of wetland/grassland species in abandoned farmland tended to be intermediate between those of their original habitats (wetland and grassland) and other land uses (forest and farmland), and to be positively associated with the landscape openness. The abundance of forest species tended to be higher in forest areas than in areas with other land use types and was not associated with the landscape openness. The abundance and species richness of the bird community were predicted to be high in large abandoned farmland areas surrounded by open land. For wetland species, whereas total abundance was predicted to be primarily mediated by landscape openness, species richness was predicted to be primarily mediated by the farmland abandonment area. The abandoned farmland in our study area would not currently have a high conservation value for forest birds. However, the abandonment of farmland surrounded by open land would significantly improve the conservation of wetland/grassland birds in the agricultural landscape. Given the decline in the area of grassland, wetland, and low-intensity farmland, farmland abandonment provides an opportunity to conserve and restore the declining populations of wetland and grassland birds.