One of the major transformations of the planet from human activities is the redistribution of species to areas outside their native
range. These “alien” species have in many cases caused substantial harmful impacts to the recipient environment. These environmental
impacts include driving native species to extinction, disrupting soil nutrient and water cycling, and altering natural disturbance regimes
like fire and flooding. Preventing and mitigating such impacts is a major drain on limited conservation resources. There is thus a
considerable need to understand which species are currently, or are likely to be, the most damaging. But how do you compare the enormous
range of impacts attributable to diverse alien taxa, acting on different levels of ecological complexity, and at different spatial and
An international team of experts, including six researchers of the C·I·B, have proposed a practical solution to this
problem. The paper, led by C·I·B Research Associate Tim Blackburn defines scenarios describing the levels of impact on
native species by different mechanisms.
Scenarios are designed so that successively higher categories reflect an increase in the order of magnitude of the particular impact
mechanism (e.g. impacts on native individuals, populations, communities), so that the magnitudes of impacts caused by different mechanisms
are directly comparable. A species assigned to a higher impact category is considered to have had a greater harmful impact on some aspect
of an environment in which it is alien, than a species in a lower impact category.
Figure 1: The different categories in the scheme to classify the impacts of alien
species, and the relationships between them.
The scheme allows for the ranking of alien species from different animal and plant groups according to the magnitude of their
environmental impacts into lists of harmful species. It is designed to be similar in structure and logic to the widely adopted
International Union for Conservation of Nature (IUCN) Red List for categorizing extinction risk.
Like the IUCN Red List, it can be used to identify priority species for action, as required by international policies on biological
invasions. The scheme provides not only a basis for decision-making, but potentially also a formal indicator of progress towards the
achievement of the aims of Aichi target 9 on the identification and management of priority invasive alien species and the pathways by
which they arrive.
The publication in the journal PLoS Biology
is one product from the sImpact workshop
which took place in July 2013 in Leipzig, with funding from the Synthesis Centre for Biodiversity sciences (sDiv) of the German Centre for
Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig. C·I·B postdoc Sabrina Kumschick was leader and convenor of the
workshop. Other outcomes of the workshop included a paper in Conservation Biology.
Read the papers:
Blackburn, T.M.; Essl, F.; Evans, T.; Hulme, P.E.; Jeschke, J.M.; Kühn, I.; Kumschick, S.; Marková, Z.; Mrugala, A.; Nentwig, W.; Pergl, J.; Pyšek, P.; Rabitsch, W.; Ricciardi, A.; Richardson, D.M.; Sendek, A.; Vilŕ, M.; Wilson, J.R.U.; Winter, M.; Genovesi, P. and Bacher, S. (2014) A unified classification of alien species based on the magnitude of their environmental impacts. PLoS Biology 12(5).
Jeschke, J.M., Bacher, S., Blackburn, T.M, Dick, J.T.A., Essl, F., Evans, T., Gaertner, M., Hulme, P., Kuhn, I., Mrugala, A., Pergl, J., Pysek, P., Rabitsch, W., Ricciardi, A., Richardson, D.M., Sendek, A., Vila, M., Winter, M. and Kumschick, S. (2014) Defining the Impact of Non-Native Species. Conservation Biology.
Charles University, Prague (Czech)
Czech Academy of Science (Czech)
University of Fribourg
Wiener Zeitung (German)
For more information, contact Dr Sabrina Kumschick at firstname.lastname@example.org