Agricultural intensification and abandonment degrade pollination services to native species via network generalization

Land intensification and abandonment are major threats to biodiversity declines in agricultural landscapes. Biodiversity declines leads to degradation of ecosystem services by altering species interaction networks. However, we still know little about the ecological processes how biodiversity declines affect ecosystem services via species interaction networks in changing agricultural landscapes. Here, we investigated quantitative 57 plant-pollinator networks in meadows around paddy terraces. We compared plant and pollinator diversity, network structure of plant-pollinator interactions, and pollination success of native and exotic plants between traditional and intensified and abandoned meadows. In the analyses, we divided plants and pollinators into life history and origin groups (native perennial, native annual, and exotic plants) and taxonomic groups (bees, syrphid and other flies, and butterflies), respectively. Intensified meadows had significantly lower native and higher exotic plant diversity than traditional meadows, whereas abandoned meadows had much lower native plant diversity. Pollinator diversity, particularly those of bees and syrphids, were significantly lower in intensified meadows, and those of all taxonomic groups were much lower in abandoned meadows. Significantly lower pollination services were observed for native perennials, while higher services were found for exotic plants via network generalization were found in both intensified and abandoned meadows, compared to traditional meadows. Moreover, the type of generalization varied between intensified and abandoned networks, likely due to the differences in scenarios of diversity loss between them. Overall, our findings suggest that both land intensification and abandonment lead to the degradation of native pollination services, despite being distinct scenarios. We recommend re-introduction of traditional extensive managements and removal of exotic plants in intensified and abandoned meadows to restore native paddy biodiversity and ecosystem services.