Balancing grazing and biodiversity : arthropod responses to modern cattle farming practices

Abstract

Ruminant production exerts severe pressure on ecosystems through land use change for pasture and fodder production, contributing to biodiversity loss, disruption of natural biogeochemical fluxes, and climate change. Whereas ruminant production can support biodiversity that has co-evolved with grasslands and grazing animals, the values of temporary grasslands are poorly understood. In this study, we assessed the effects of grazing regimes practised on modern cattle farms, including no grazing, on the abundance, biomass, and taxonomic richness of aerial and ground-dwelling arthropods. We assessed the potential value of organic management compared to grazing on conventional farms, and the role of vegetation structure on the pastures. We sampled arthropods in temporary pastures and silage grasslands, spring cereal fields, and in farmyards on 43 dairy and suckler cow farms in Finland. We show that grazing benefits the richness of ground-dwelling arthropods in fields, and the benefits were most evident at extensive levels of grazing at the farm scale. Grazing had no significant benefits for the biomass of ground-dwelling arthropods or relative abundance of aerial arthropods over field vegetation. Grazed rotational grasslands had similar levels of arthropods as mown grasslands or cereal crops, except for a higher richness of ground-dwelling arthropods. Taxonomic richness of ground-dwelling arthropods was higher on organic farms than conventional, but only at low grazing intensities. Although our study suggests several ways in which livestock farmers can maintain and increase arthropod populations on their farms, these may be associated with some reduction in production output on modern farms oriented towards high yields