Controlling invasive species in complex social landscapes

Control of biological invasions depends on the collective decisions of resource managers across invasion zones. Regions with high land-use diversity, which we refer to as "management mosaics", may be subject to severe invasions, for two main reasons. First, as land becomes increasingly subdivided, each manager assumes responsibility for a smaller portion of the total damages imposed by invasive species; the incentive to control invasives is therefore diminished. Secondly, managers opting not to control the invasion increase control costs for neighboring land managers by allowing their lands to act as an invader propagule source. Coordination among managers can help mitigate these effects, but greater numbers and a wider variety of land managers occupying a region hinder collective action. Here, we discuss the challenges posed by management mosaics, using a case study of the yellow starthistle (Centaurea solstitialis) invasion in the Sierra Nevada foothills of California. We suggest that the incorporation of management mosaic dynamics into invasive species research and management is essential for successful control of invasions, and provide recommendations to address this need.