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.
A total of 5789 plant species were classified as alien. Of these, 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 (http://www.europe-aliens.org/). Research institutes and organisations from 15 nations were involved in the project.
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