Habitat area and connectivity support cavity-nesting bees in vineyards more than organic management

Abstract

The expansion and intensification of agriculture are the main causes of current insect declines. Pollinators like cavity-nesting bees can be limited by reduced nesting and feeding opportunities in farmland. As insects constitute the bulk of terrestrial biodiversity and fulfill important ecological functions, there is an urgent need to identify ways to combine agricultural land use and insect conservation. Perennial crops like grapevine can provide permanent habitats for numerous beneficial organisms including various pollinators. With their dominating character in viticultural areas and >7 million ha covered by vines globally, their potential to contribute to nature conservation should be more widely considered. We compared effects of organic management, inter-row vegetation characteristics and landscape parameters on the abundance and species richness of cavity-nesting bees in Central German vineyards. In a paired study design, we assessed cavity-nesting bees in 15 pairs of organically and conventionally managed vineyards along a gradient of landscape complexity. We found that organic management, even though it enhanced flower availability in the vineyards, was only partially beneficial for cavity-nesting bee abundance. Abundance and species richness were enhanced by either semi-natural habitat area or proximity of woody elements like hedges or forest remnants, most likely due to the nesting demands of this particular group of pollinators. We conclude that vineyards can help to sustain cavity-nesting bee abundance, given that landscapes are managed accordingly. We recommend maintaining or establishing woody elements between vineyards, which is likely to also benefit additional groups of organisms such as breeding birds in viticultural landscapes.