Migrating plants - a threat to native species?
The butterfly bush is a fast-growing ornamental shrub from China, which has become very popular among European gardeners because of its ability to attract butterflies, bees and ladybirds. However, researchers from the Helmholtz Centre for Environmental Research (UFZ) have discovered a darker side to this shrub. The UFZ researchers compared 10 populations of buddleia in Germany with 10 populations in its original homeland, the south west Chinese province Yunnan. Although the climatic conditions are more favourable in China, the bushes were larger in Germany and produced more and heavier seeds. Reasons for their propagation could be genetic changes or the fact that herbivores, such as insects, must first adapt to the new plants before they can eat them. 'From the plants in the Chinese homeland, 15% of the leaves had been eaten by insects. By comparison, in Germany only 0.5%,' commented Susan Ebeling from the UFZ. 'The intruder is not yet on the menu for our insects. Because there are no relatives of buddleia in Central Europe, the insects need longer to adapt.' Because there is little risk of being eaten, the fast-growing shrub has the potential to displace native species of plants and could therefore pose a threat to the ecological balance, say the German researchers. Their findings are published in the scientific journal Diversity and Distributions. The shrub is also becoming a safety risk along railway embankments where it has been recorded as growing. Countries such as France, Spain and Switzerland are trying to combat buddleia, while in the US its propagation is being observed critically. Meanwhile in New Zealand, the shrub is causing economic problems because it suppresses native vegetation. Ornamental shrubs and cultivated plants constitute a majority of the alien plant species that have become a problem and are therefore referred to as biological invaders by specialists. Biological invasions caused by humans are one of the causes of the dramatic world-wide decrease in animal and plant species. According to a study conducted by Germany's Federal Environment Agency, the economic costs of 20 alien species investigated amounted to approximately €167 million in the year 2002 in Germany.
Countries
Germany