High nature value farmland increases taxonomic diversity, functional richness and evolutionary uniqueness of bird communities

In an attempt to mitigate the decline of biodiversity, the European Union introduced the high nature value (HNV) farmland concept into the Common Agricultural Policy (CAP). The rationale was to reinforce biodiversity conservation through the maintenance of traditional low-intensity farming systems. HNV farmland is in fact defined as a system which includes semi-natural habitats, low intensity farming and diverse, small-scale mosaics of land-use types, comprising hotspots of biological diversity. However, until now few studies have focused on the degree to which HNV farmland as defined and identified through a set of farming practices and/or farmland typologies is successful in supporting biodiversity.The values of taxonomic diversity, functional diversity and evolutionary distinctiveness of breeding bird communities between HNV and non-HNV farmland were compared in Central Italy.Bird species richness and functional richness were higher in HNV than in non-HNV farmland. HNV farmland supported bird communities 27% more unique in terms of phylogenetic diversity than non-HNV farmland. A combination of land cover composition (land use coverage) and configuration (spatial arrangement of patches) differentially affects each component of bird diversity. Variation in species richness was explained by land use composition (31%) and shared contribution between land use composition and landscape metrics (13%). The functional diversity of bird communities was little explained by changes in land cover of farmland (less than 14%). As a conclusion, I highlight that HNV farmland needs to be protected because it supports bird communities characterized by high overall bird diversity. Conservation planning should pay attention to the relative association of farmland features with each component of bird diversity.