No control without measurement

Blackburn et al. propose a categorization system to understand the nature and extent of damage caused by non-native species. Their “semi-quantitative” (their word) metric bins species (within a defined area, small or large) into one of five levels of impact, from Minimal (“unlikely to have caused deleterious impacts”) to Massive (“leads to the replacement and local extinction of native species”). They also identify 12 categories of impact, ranging from effects we see frequently in the mid-Atlantic (Competition, Parasitism) to some more obscure ones (Flammability, Bio-fouling).

Good stuff. This is a lot more sophisticated than just tarring everything with the broad brush of “non-native invasive.” And, as the authors point out,

invasiveness… is a characteristic of a population rather than a species.