Significant increase in alien plants in Europe

September 17, 2008
Among the most widespread of the new plant species is the Canadian fleabane (Conyza canadensis), which originated in North America. Photo: André Künzelmann/UFZ

The number of alien plant species has more than tripled over the last 25 years. This is the finding of a study by European scientists who evaluated the data from 48 European countries and regions. 5789 plant species were classified as alien. 2843 originating outside of Europe, according to the researchers and their publication in the journal Preslia. By contrast, in 1980 only 1568 alien species were registered.

Of these, 580 had come from outside Europe. According to the researchers, around six new species arrive in Europe each year on average. This inventory of information about alien species is designed to help developing Europe-wide management strategies and tools of risk assessment to protect biodiversity. New species that bring about long-term changes to ecosystems by e.g. competing with native species, are regarded as one of the greatest threats to biodiversity.

The highest numbers of alien plant species were reported from Belgium, the UK and the Czech Republic. The UK, Germany and Belgium have the greatest numbers of naturalized aliens, new species that have been able to establish stable populations. Among the most widespread of the new plant species are Canadian fleabane (Conyza canadensis), Jerusalem artichoke (Helianthus tuberosus) and black locust or false acacia (Robinia pseudoacacia), which all originated in North America. More than three-quarters of all new plant species have been brought to Europe unintentionally.

Not only can new plant species threaten the native flora, there can also be economic costs involved, as is the case with common ragweed (Ambrosia) for instance. Ragweed originated in North America and has already spread to large parts of Europe. Its pollen is one of the most aggressive allergens. Initial estimates for Germany put the annual costs associated with just three of the 470 most widespread neophytes at around € 70 million.

As part of the EU project DAISIE (Delivering Alien Invasive Species Inventories for Europe), all known alien species in the countries of Europe were documented for the first time. Information on the ecology and spread of alien plants and animals was collected and made available via an online database to anyone with an interest in the subject ( Research institutes and organisations from 15 nations were involved in the project.

The largest ever conference of ecologists from all over Europe is taking place in Leipzig from 15 to 19 September 2008. Over 1000 participants from more than 30 countries have registered for EURECO-GFOE 2008. The conference is a joint meeting of the European Ecological Federation (EEF) and the Gesellschaft für Ökologie (GfÖ) and is being organised at the Congress Center Leipzig by the Helmholtz Centre for Environmental Research (UFZ) and the Universities of Halle-Wittenberg and Leipzig. The EEF is the umbrella organisation of the national ecological associations in Europe. Over 8000 ecologists belong to its member associations. The GfÖ is the ecological society of Germany, Austria and Switzerland.


Lambdon, P, Pyšek, P., Basnou, C., Arianoutsou, M., Ess, F., Hejda, M., Jarošík, V., Pergl, J., Winter, M., Anastasiu, P., Andriopoulos, P., Bazos, I., Brundu, G., Celesti-Grapow, L., Chassot, P., Delipetrou, P., Josefsson, M., Kark, S., Klotz, S., Kokkoris, Y., Kühn, I., Marchante, H., Perglová, I., Pino, J., Vilà, M., Zikos, A., Roy, D., Hulme, P. (2008): Alien flora of Europe: species diversity, temporal trends, geographical patterns and research needs. Preslia 80: 101-149.

Source: Helmholtz Association of German Research Centres

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