Land consolidation negatively affects farmland bird diversity and conservation value

Abstract

Land consolidation can negatively affect biodiversity, as it is usually followed by the expansion of arable land, a decrease in crop and land cover diversity, and an increase in the application of agrochemicals. The aim of our study was to compare the species’ composition and abundance of farmland birds, as well as habitat structure, on consolidated and non-consolidated sites in Goričko, NE Slovenia. Habitat diversity was much lower on consolidated sites compared to non-consolidated ones, with arable fields and associated habitats (e.g. grass field margins, field tracks) prevailing on the former. Non-consolidated sites held higher proportions of different types of meadows, hedgerows, solitary trees, succession and traditional orchards. Farmland bird diversity and the abundance of a majority of farmland bird species were higher on non-consolidated sites. The only two exceptions to this were the Eurasian Skylark and the Common Stonechat, which were more abundant on consolidated sites. Both of the species suffered population declines at Goričko in the period 1997–2016, bringing into question the suitability of intensively managed arable fields as their breeding and foraging habitat. Individual species’ regression analysis revealed that the most influential positive explanatory variable for the presence of Red-backed Shrike, Tree Sparrow and Common Whitethroat was non-consolidated, extensively managed mosaic landscape, whereas for the Yellowhammer this explanatory variable was superseded only by forest islands without traditional orchards. Land consolidation, as performed in Slovenia, negatively affects farmland bird diversity and its European conservation value, which is why it should not be performed on Natura 2000 sites, designated for nature conservation.