The world is getting smaller all the time, and one consequence of this phenomenon is that species are increasingly spreading to new regions and being introduced to new areas. These alien species can cause devastating problems, but while many invasive animals and plants have a negative impact on biodiversity and local economies, they can also be beneficial.
Considered one of the most prominent types of invasive species, raccoons have been resident in Germany for 84 years now. Originally brought as pets from North America, around one million raccoons now live in Germany, where they are considered a menace: They threaten native bird species and are believed to be responsible for spreading diseases such as rabies.
New species like this can become a problem. Experts classify species as invasive when they breed and spread very quickly in a new habitat where there are no natural predators. This can cause an overabundant population, which ultimately out-competes native species. This phenomenon occurs in between 5 and 20 percent of all non-indigenous species. In the EU, 23 invasive animal species and 14 plant species are currently classified as species of union concern, which means they threaten biodiversity and necessitate control through international measures.
Invasive species are often one of the factors responsible for declining biodiversity within ecosystems. Overall, they are the second most common cause of species extinction, and according to the International Union for Conservation of Nature (IUCN), they are the main cause of the disappearance of species in amphibians, reptiles and mammals.
These invaders not only harm an area‘s overall biodiversity, but they can also negatively impact the economy. One example is the quagga mussel, now widespread throughout the world, which overgrows water pipes, thus causing blockages and outages in waterworks. The EU member states alone spend a total of between EUR 9.6 and 12.7 billion per year on repairing damage caused by invasive species.