When is a “wait and see” approach to invasive species justified?

► Invasive species are classified into immediate action and a “wait and see” approach. ► Species that spread fast in a very unpredictable fashion require immediate action. ► Species that spread slowly in a predictable fashion may require a “wait and see” approach. ► Economic uncertainty has a minimal effect on policy timing and stringency. ► Spread uncertainty will delay a completely irreversible action but hasten a partially irreversible action.