Bioinvasions in fresh waters and the Nero dilemma.

Human-mediated invasions of organisms are causing great harm to the environment, indigenous species, national economies, and human health. Notwithstanding Elton’s (1958) prophecies, only by the mid 1980s did the negative impact of several introduced species become clear, along with the urgency to reduce the pace of bioinvasions. Often conservation biologists are faced with the Nero dilemma. Should they keep “fiddling” with their elegant experiments while biota are burning, or rather act, even before achieving a “strong verification” of their hypotheses? Indeed, we do need a comprehensive scientific understanding of the biological features, ecological effects, and spread potential of invasive species in order to be able to improve our strategies for mitigating their impacts. Abundant data have been collected during the past two decades on a growing number of case studies. The theories on bioinvasions derived from that wealth of knowledge have indeed revealed their predictive power. We should now strive towards a quick transfer of this knowledge from the laboratories to the real world.