Dark invasions as cryptic components of biological invasions

Jingrui Sun , Teun Everts, Ronaldo Sousa, Ismael Soto Almena, Philip E. Hulme, J. Robert Britton, Phillip Joschka Haubrock

Understanding and managing biological invasions typically requires knowledge of species records, known impacts, recognized pathways and definitions of non-native status, yet this information is rarely complete or without uncertainties. We develop the concept of dark invasions to describe a suite of hidden or underacknowledged aspects of biological invasions that are rarely quantified because species, pathways, distributions, spread dynamics or impacts are undetected, misidentified, biogeographically unresolved, temporally delayed, poorly attributed or excluded by regulation. We characterize dark invasions as resulting from six interacting components of uncertainty: taxonomic, biogeographic, temporal, detection, impact, and regulatory. We describe how each component of dark invasions can cause invasion risks to be underestimated across monitoring, research, management, and policy activities. Dark invasions complement and integrate existing concepts, such as cryptic invasions, lag phases, invasion debt, and impact debt within an overarching concept centralized around the mismatch between recorded invasion data and realized invasion risk. We argue that some components of dark invasions can at least partially be mitigated through emerging technological approaches, and that the dark invasion concept can guide detection-based, uncertainty-based and inference-based assessments, while promoting more proactive, ecologically grounded biosecurity. Recognizing dark invasions can contribute to shifts in research, management and policy, moving from a reactive approach addressing well-known invaders towards a proactive and anticipatory approach that acknowledges uncertainties and addresses hidden invasion risks before they become detectable.