Recently, invasion biologists have argued that some of the skepticism expressed in the scientific and lay literatures about the risks of invasive species and other aspects of the consensus within invasion biology is a kind of science denialism. This paper presents an argument that, while some claims made by skeptics of invasion biology share important features with paradigm cases of science denialism, others express legitimate ethical concerns that, even if one disagrees, should not be dismissed as denialist. Further, this case (...) illustrates a more general point about ethical disagreement within sciences like invasion biology that constitutively pursue non-epistemic goals and values. While philosophers of science have argued that epistemic disagreement within science can be productive as heterogeneous epistemic communities “hedge their bets,” the case of invasion biology shows how non-epistemic or ethical disagreement within sciences, while carrying significant risks, can also be epistemically and non-epistemically valuable. (shrink)