Reconciling the control of the native invasive Jacobaea aquatica and ecosystem multifunctionality in wet grasslands

Grasslands are managed to provide multiple goods and services. During recent decades, abandonment of marginal grasslands and intensification of the most productive sites resulted in biodiversity losses and reduced ecosystem services (ESs). Moreover, invasion by unwanted plants impaired ESs, as seen in Jacobaea aquatica, a poisonous native invader in pre-alpine grasslands of Central Europe. Invasion by this plant compromises fodder quality and endangers animal health, resulting in abandonment of grassland use. We tested different management regimes to reduce J. aquatica in wet grasslands of Southern Germany and assessed how its regulation affects grassland multifunctionality. We monitored indicators associated with productivity and conservation, such as the abundance of J. aquatica, forage quality, yield, abundance of specialists, and pollinator-relevant plants. Intensive management favoured multifunctionality by promoting productivity and biodiversity, yet also increasing the abundance of J. aquatica. Reduced management regulates J. aquatica cover close to an acceptable threshold while also reducing ESs. Thus, we conclude that moderate management strikes a balance between the control of the poisonous plant and the supply of grassland multifunctionality.