Shared ecological knowledge about the impacts of biological invasions can facilitate the collective action necessary to achieve desired management outcomes. Since its introduction to an island archipelago in South America, the North American beaver has caused major changes to the ecosystem. We examined landowners’ mental models of how beavers impact ecosystem services in riparian areas to understand the potential to implement a large-scale eradication program. We used ethno- graphic interviews to characterize individual landowners’ perceptions about beaver-caused changes to ecosystems and landowners’ wellbeing, and examined the degree to which they are shared. While the eradication initiative focuses on ecosystem integrity, landowners considered impacts on provisioning ser- vices to be most salient. Landowners did not have a highly shared causal model of beaver impacts, which indicates a diverse knowledge system. This lack of consensus on how beavers impact riparian areas provides some optimism for garnering support for eradication, and also offers insights into challenges with mental modeling methodologies.