GLAND There are over 12,000 alien animal and plant species in Europe, ranging from the North American grey squirrel, red-eared terrapin and grass carp to the highly dangerous Asian hornet and tiger mosquito. They are causing €12 billion worth of damage annually and pose an ever-growing threat to biodiversity and health.
Walking around ponds and swamps in the Lake Geneva region, such as at the Aubonne Arboretum, the Bois de la Bâtie in Geneva or where the Rhone enters the lake near Villeneuve, you can often see turtles sunning themselves or searching for food in the shallows. These are probably not the rare European pond turtle, or cistude, but rather the rapacious American red-eared slider – those green little terrapins originally brought over by the pet trade and now found throughout Europe. While the red-ears are not thought to have established breeding populations in Switzerland, they can live as long as a human, grow to 30 cm in length and prey on water fowl, fish and frogs. They are also pushing out the country’s only native terrapin.
Other invaders include the North American racoon (introduced to Germany during the 1930s), grey squirrel (now overrunning the native red species), racoon dog (from north-eastern Russia), the South American coypu, or nutria, and North American muskrat (both brought over for the fur industry), American catfish, bullfrog, various species of Asian and American crayfish, and even the exotic mandarin duck from China.
Many can spread disease, kill nesting birds, or ruthlessly compete with other species. Out of the 28 types of fish in Lake Geneva, half are considered invasive such as rainbow trout, sunfish and even giant goldfish or koi. The Thai chipmunk, in northern Italy has encroached to within three kilometres of the Swiss border. It carries diseases such as Lyme disease. Some animals, notably the Italian crested newt, escaped from a Geneva research station and have how completely displaced the local great crested variety.
Last month, the European Union introduced an action plan to counter problematic plants and animals introduced to the wild by humans. “Not all invasive species are bad, so the main focus is to protect biodiversity and to counter those that are a problem,” noted Piero Genovesi, who heads up the specialist Invasive Species Group at IUCN in Gland and is a scientist at the ISPRA environmental institute in Italy. “The only way to do this is through concerted prevention on a European-wide basis.”
For Wolfgang Nentwig of the Institute of Ecology and Evolution at Bern University, which produces DAISIE, the European invasive species inventory, such species have become more frequent because “space and resources are limited; someone else has to disappear”. “Clearly, one cannot stop all species, but one can introduce effective management to reduce their spread,” said Genovesi. “It’s also a matter of informing people properly. Locally, one does not see a huge change, but globally it means the 50 native bird species in Hawaii that have been replaced by 50 outsiders.”
The problem is expected to worsen as climate change encourages some species to move north. One of these is the deadly Asian giant hornet, which consumes 50 honey bees a day, threatening honey production and pollination. Highly venomous, it has already arrived in northern Italy and is expected to cross into Switzerland soon. “The hornet could spark a general crisis with other pollinators of fruit trees and other forms of agricultural production, which are crucial for human survival.”
“The issue is that we never seem to learn from our mistakes,” said Genovesi.
Hence the need to focus on prevention, including rules to inhibit the import of certain species before they can become established. It is also necessary to react rapidly. Canadian beavers released in the wilds of France were removed in a matter of weeks. In other situations, it is too late to act. The golden jackal, which is spreading naturally and through quick adaption from the Mediterranean, has now arrived in Switzerland and Italy and is moving toward Estonia and Hungary, probably as a result of climate change rather than direct human intervention.