Green Covers Effectively Increase Arthropod Biodiversity in Orchards, Even at High Management Intensity

Abstract

Agri-environmental measures such as wildflower strips and green covers are a key instrument to halt biodiversity loss and enhance the delivery of biodiversity-based ecosystem services in farmland. Agri-environmental measures produce mixed biodiversity benefits and it has been hypothesized that this is partly due to the moderating effects of farm management intensity. However, contrasting hypotheses exist suggesting both positive and negative effects of management intensity on the ecological effectiveness of agri-environmental measures. To improve our understanding of the relation between farm management and effects of measures under real world conditions, we established flowering green covers in 15 Spanish stone fruit orchards varying in management intensity. In paired green cover and conventionally managed plots within the same orchards, we sampled arthropod pollinators, predators, and parasitoids, as well as flowering plants. Abundance and species richness of all functional groups was consistently higher in green covers compared to control alleys. The effectiveness of establishing green covers increased with management intensity for pollinators and flowers, but not for predators and parasitoids. Our results suggest that, depending on the target species group, agri-environmental measures are at least equally effective, if not more effective, when farm management intensity is high. Therefore, the hypothesized negative impact of high-intensity farm management on agri-environmental measure effectiveness does not justify reallocating budgets away from more intensive farms. Implementing agri-environmental measures in highly intensive farmland is valuable, especially considering their potential to provide ecosystem services, and the urgent need for action in exactly these areas where biodiversity is most severely degraded.

Keywords: green covers in stone fruit orchards, agri-environmental schemes, management intensity, beneficial arthropods