A new global scheme to rank invading species according to their environmental impact will provide a simple method for comparing very different species.
The system has been developed by a global team of ecologists and conservationists, including Philip Hulme from Lincoln University and the Bio-Protection Research Centre, who says “I don’t think there’s any part of the world that doesn’t suffer from these introduced alien species including the Antarctic … We felt it was time for us to derive a system whereby you could rank species not in terms of their monetary value, but in terms of their potential impact on biodiversity, ecosystems and endangered species.”
The proposed system is outlined in a recent paper in the journal PLOS Biology – ‘A Unified Classification of Alien Species Based on the magnitude of their Environmental Impacts’ (vol 12 issue 5 May 2014). The global ranking system will be similar to the existing IUCN Red List, which ranks threatened species, and some commentators have noted it could produce equivalent Black Lists of invasive species.
The system recognizes five levels of impact – massive, major, moderate, minor or minimal – across a number of impact classes, including herbivory, competition, predation, disease transmission, hybridization,parasitism, bio-fouling, poisoning, interaction with other alien species and chemical, physical or structural ipact on an ecosystem. Each invasive species is given a ranking within each impact class, and its final overall rank is simply the mechanism with the highest impact.
Philip Hulme says “what we wanted was a mechanism by which you could say ‘what’s worse, broom or Argentine ant in New Zealand?’ Could we start valuing different organisms along a similar kind of metric so we could start prioritizing species across taxa.’
The proposed system has been presented to the International Union for the Conservation of Nature (IUCN) for its consideration.