Shifting paradigms in the history of classical biological control

Classical biological control using insects has led to the partial or complete control of at least 226 invasive insect and 57 invasive weed species worldwide since 1888. However, at least ten introductions of biological control agents have led to unintended negative consequences and these cases have led to a focus on risk that came to dominate the science and practice of classical biological control by the 1990s. Based upon historical developments in the field we consider that the era of focus on benefits began in 1888 and that it was supplanted by an era in which the focus was on risks during the 1990s. This paradigm shift greatly improved the safety of biological control releases but also led to a decline in the number of introductions, probably resulting in opportunity costs. We note here the development of a third paradigm: one in which the benefits and risks of biological control are clearly and explicitly balanced so that decisions can be made that maximize benefits while minimizing risks.