Non-native species are a major component of global environmental change, and aquatic systems are especially vulnerable to non-native species impacts. Much of the research on aquatic non-native species impact has occurred at the local or site level. In reality, non-native species impacts play out across multiple spatial scales on heterogeneous landscapes. How can we ‘scale up’ our understanding of site-level impacts to the broader landscape scale? To address this disconnect, we synthesize our current understanding of key components of landscape-scale non-native species impacts: geographic range, abundance, and local impacts. Most aquatic non-native species have small ranges, while a few have large ranges. However, aquatic non-native species are often far from saturated on landscapes, and occurrence records are often woefully incomplete. Aquatic non-native species are often at low abundances where they are present, reaching high abundance in a small number of locations. Finally, local-scale impact can be estimated from abundance, but this requires knowledge of the abundance–impact relationship. Considering these multiple components enables understanding of non-native species impacts at broader spatial scales. Although the landscape-level impacts of aquatic non-native species may be high, the spatial distribution of site-level impacts is uneven, and highly impacted sites may be relatively uncommon. This heterogeneity in impacts provides an opportunity to optimize and prioritize non-native species management and prevention efforts.
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Thanks to the colleagues who have contributed to the research and ideas presented herein: Matt Kornis, Alison Mikulyuk, Jake Walsh, Mona Papes, Sapna Sharma, Julian Olden, and Tony Ricciardi. Alison Mikulyuk provided maps. Special thanks to colleagues at the Wisconsin Department of Natural Resources: Scott Van Egeren, Bob Wakeman, Maureen Ferry, and Tim Asplund. This work was supported by the Wisconsin Department of Natural Resources and the National Science Foundation (#CNH-0909281 and #DEB-1440297, NTL-LTER).
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