No more silent (and uncoloured) springs in vineyards? Experimental evidence for positive impact of alternate inter-row management on birds and butterflies.
Agricultural intensification is a main threat to biodiversity, and vineyards are particularly concerning because of their increasing extent and intensive management. Management strategies that mitigate vineyard impacts on biodiversity are urgently needed. In a major wine area in northern Italy, we tested in a 3-year experiment the effect of alternate management of vineyard ground cover (mowing or tillage depending on the usual management system adopted by each farmer). After a first year (2017) with no implementation (baseline), in the two subsequent spring-summer periods (2018 and 2019), alternate management was adopted in a varying number of sites, providing an ideal BACI design. Birds and butterflies were selected as target groups, and surveyed by means of 200-m linear transects scattered over both conventional and organic vineyards, with and without alternate management. We evaluated whether the implementation of alternate management resulted in an increase in species richness per transect. We also evaluated the effect of alternate management, year and land cover on different functional avian guilds (functional insectivores, seed eaters, potential grape eaters), considering both richness and abundance. For both birds and butterflies, we found a positive effect of alternate management on the number of species per transect. The implementation of alternate management also promoted richness and abundance of functional insectivores and abundance of seed eaters; a positive but less supported association was also found between alternate management and richness and abundance of potential grape eaters. The most relevant land cover for the supply of ecosystem services by birds was likely shrubland cover, which increased richness and abundance of insectivores and seed eaters, while not supporting potential grape eaters. Farmers reported no adverse effects of alternate management, and a positive impact on farm perception by consumers. Synthesis and applications. The very easy-to-implement alternate inter-row management has the potential to rapidly increase the suitability of vineyards for biodiversity, while enhancing ecosystem services and attractiveness of farms for nature-based recreation, contributing to their multi-functionality. Alternate management could contribute to shape, for example, new interventions within the coming Common Agricultural Policy, and its benefits may be maximized by sympathetic landscape strategies.