Assisted colonization: evaluating contrasting management actions (and values) in the face of uncertainty

In their recent Opinion article in Trends in Ecology & Evolution, Ricciardi and Simberloff argue that assisted colonization is not an appropriate management option because the impacts of introduced species are too difficult to predict, and can have harmful consequences for recipient ecosystems, including the extinction of native species. Invoking the precautionary principle, the authors argue that alternative conservation tactics must be pursued, even for species faced with extinction in their native range. We concur with the authors that there are risks associated with introducing species outside of their current range. However, we disagree that these risks are so great that assisted colonization should not be considered among possible management options.