Progress in our understanding of impacts is often hampered by a lack of data, and complicated by the diversity of measures applied to quantify impacts. Impact scoring schemes have been developed to make this variable data comparable between different methods used and measures taken, but also between taxa and regions. This enables us to explore spatial patterns in alien species impacts, and to answer questions more broadly on which factors contribute to impact magnitude. This includes species traits (for example fecundity and native range size), recipient habitats (e.g., grasslands vs. forests), or impact mechanisms used (like competition and hybridisation).
One of the most popular impact scoring schemes is the Environmental Impact Classification for Alien Taxa (EICAT). It has been endorsed by the IUCN to be used alongside the Red List of Threatened Species to support the conservation of biodiversity. EICAT classifies alien species according to the magnitude of the impacts caused into one of the following categories: DD – data deficient; MC – minimal concern; MN – minor; MO – moderate; MR – major; and MV – massive. Each impact level is linked to a different level of organisation in the affected native community, reaching from individuals over populations to communities.
Results/Conclusions
A variety of taxa have been assessed to date, including all alien birds and amphibians globally, and selected plants, invertebrates and other vertebrates. The growing number of taxa assessed confirms the broad applicability of EICAT, and contributes to a growing database of alien species’ impacts. The studies also contributed to various hypotheses in invasion science. For example we found that native/alien status does not determine impact magnitude in bamboos, and grasses alien to South Africa on average cause similar magnitudes of impact in all habitats they invade. Unsurprisingly, alien mammals have shown to cause more severe impacts on islands, and a similar trend was found for alien birds, contributing to the island susceptibility hypothesis. Beside these more theoretical applications, EICAT has been suggested as a decision support tool for management of alien species.
I am going to present results of studies using EICAT as well as other applications related to policy making, and discuss strengths, weaknesses, threats and opportunities of using a generic impact scoring scheme to tackle these issues.