How far do invasive species travel?

Date: January 11, 2017

Source: Senckenberg Research Institute and Natural History Museum

As a result of the globalization of trade and transport, in the past decades, tens of thousands of species have spread into regions where they were not originally at home. Potentially serious consequences of this include the displacement or extinction of native species and the spread of health risks. Even though trade flows are known to represent an important path for the introduction of invasive species, this fact alone is not enough to explain the observed distribution patterns of species.

Scientists from Germany and Austria have examined the global spread of 1,380 exotic animal and plant species under consideration of the trade flows. "A clear pattern is apparent. A particularly large number of species originates in areas that are located at a distance of approximately 10,000 kilometers from the place of introduction. Contrary to this, the majority of the imported goods come from the immediate neighboring countries," explains Dr. Hanno Seebens of the Senckenberg Biodiversity and Climate Research Center.

In order to study this apparent contradiction, the team developed a computer model that combines the international trade flows with the species' worldwide distribution. The model shows that short distances of less than 3,000 kilometers primarily serve the transport of species that already occur in the target country. On the other hand, non-native species are usually introduced over comparatively much longer distances.

Here, the global patterns of the species' spread closely mirror the global trade flows. However, this only holds true when a species conquers new ground for the first time. Once an exotic species has gained a foothold outside its region of origin, it can also spread to new areas over short distances.

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