Plants and animals are increasingly spreading - humans in particular are contributing to the introduction of non-native species. A team of scientists from Oldenburg has now discovered what pattern the spread follows.
Around the globe, more and more plant and animal species are being introduced into new regions by humans. The patterns of dispersal were previously poorly understood. A team of researchers from the University of Oldenburg, the Senckenberg Biodiversity and Climate Research Centre in Frankfurt and the University of Vienna has discovered that the spread of species can be explained very well by a combination of global trade flows and the original distribution of species. Contrary to previous assumptions, the spread of non-native species basically follows simple laws.
Due to the globalisation of trade and transport, tens of thousands of species have spread around the world in recent decades to areas where they are not actually native. Possible serious consequences include the displacement or extinction of native species or the spread of health risks. Even though trade flows are known to be an important pathway of introduction, this alone cannot explain the observed spread of species.
The experts from Oldenburg, Frankfurt and Vienna have analysed the global spread of 1,380 foreign animal and plant species with a view to trade flows. "There is a clear pattern. A particularly large number of species come from areas around 10,000 kilometres away from where they were introduced. In contrast, most of the imported goods come from directly neighbouring countries," says Dr Hanno Seebens from the Senckenberg Biodiversity and Climate Research Centre in Frankfurt.
To investigate this apparent contradiction, the team developed a computer model that combines international trade flows with the global distribution of species. It shows that mainly species that also occur in the destination country are transported over short distances of less than around 3,000 kilometres. Non-native species, on the other hand, are imported over comparatively long distances.
Here, the global dispersal flows of the species reflect the global trade flows very well. However, this only applies when the species conquers new soil for the first time. Once a foreign species is outside its original region, it can also reach other regions over short distances.
The way in which the "newcomers" spread is different for plants and animal groups. Mammals, reptiles and fish spread particularly frequently over shorter distances (3,000 kilometres). Plants and birds tended to conquer more distant areas.
"The spread of non-native species is a complex process and the data is far from complete. It is therefore all the more astonishing that the spread can be explained using simple models," says Prof Dr Bernd Blasius from the Institute of Chemistry and Biology of the Marine Environment (ICBM) at the University of Oldenburg and continues: "This gives us hope that the introduction of alien species can be better understood and more efficiently contained in future with the help of such models."