Reduced diversity of farmland birds in homogenized agricultural landscape: A cross-border comparison over the former Iron Curtain

Abstract

Agricultural intensification led to a transformation of structurally complex agricultural landscapes that resulted in a subsequent loss of landscape heterogeneity. Landscape homogenization is considered a crucial process which influences farmland biodiversity; however, separating the effects of homogenization from other environmental gradients is difficult and rarely tested. This study aimed to compare farmland bird communities in two cross-border regions (Austria and the Czech Republic) across the former Iron Curtain that have a similar share of arable land and non-crop habitats, but markedly differ in landscape homogenization. Due to historical differences in political and socio-economic systems, the farmland in Austria is dominated by small-scale farming, whereas large-scale farming is characteristic of the Czech Republic. Using two independent datasets (i.e., point-counts and transect-counts), we found substantially (ca. 1.5-fold) higher abundance and species richness of farmland birds in Austria compared to the Czech Republic. Most of the farmland bird species (although not all) were significantly more abundant in Austria in comparison to the Czech Republic and none showed a reversed pattern. A positive association between landscape heterogeneity and farmland bird diversity suggests that conservation measures promoting small and fragmented crop fields over large ones and increasing field margins may be an effective measure to increase declining farmland biodiversity. Financial support for the agricultural production of small-scale farming agroecosystems may be an option.