Number of the Month: 16 percent

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What is bright green, sits in trees and makes a terrible din? That’s an easy question to answer for many people living in southern Germany: ring-necked parakeets. These descendants of birds that escaped from captivity are now taking full advantage of their freedom in the region’s wetlands. Originally from India and North Africa, the birds have adapted to the German climate. Ring-necked parakeets are introduced species – animals and plants that have found a new home for themselves. Up to 16 percent of all species of plants and animals have the potential to migrate, as a team of scientists led by Dr Hanno Seebens at Senckenberg Biodiversity and Climate Research Centre in Frankfurt am Main discovered. Brought to a new environment, whether intentionally or not, they become established there. Other examples of introduced species include Himalayan balsam and the racoon – an animal originally from North America that escaped from fur farms. There are more than a million of these carnivores in Germany, estimates Seebens.

Globalisation is changing the world

28 percent of these non-native species that have settled in particular regions are "new", and are also known as invasive species or neophytes. They are species that are registered for the first time outside their original habitats, explains the Frankfurt-based scientist. "We are seeing a lot more nowadays than was the case a hundred years ago." Though there are many reasons for this, it has a lot to do with the significant increase in mobility. "Through our global trade, we are changing the world", says the researcher. And he urgently recommends that we minimise our interventions in nature.

The seeds of non-native plants are transported in cars and trains, for example. It is above all species already in the country that are disseminated in this way. They have just as little respect for national boundaries as did the seeds of exotic plants that were brought to royal botanic gardens in the late nineteenth century and were then blown over the walls by the wind. Giant hogweed for instance, a phototoxic plant that was once introduced to gardens in England and Germany from the Caucasus because of its size and magnificent blooms, has long been considered a "pest" that has a huge impact on other plants.

A catalyst for this interchange of species

The expansion of transportation networks via rail, ship or road and the opening up of remote regions for trade has played the biggest role in disseminating such non-native species, however. Early explorers and settlers had already taken animals and plants with them to other continents, but it is today’s thriving global trade that has truly served as a catalyst for this interchange of species. All kinds of plants and animals travel undetected around the globe on board container ships. Stories about huge spiders being discovered in boxes of bananas are told from time to time, but normally it tends to be tiny insect larvae in wooden pallets that are reported by experts who are called in for help when forests are devastated by pests.

Fruit from far-flung corners of the world

One major problem, according to Seebens, is the ballast water carried on board cargo ships. Used to balance the vessel, it is full of everything from microbes to small fish. Though this water can be cleaned, it is a complex and laborious process. In 20 years’ time at the latest, however, cleaning is to be made compulsory. Governments and ship owners have recognised the problem. As Dr Hanno Seebens explains, an awareness of the problem – even among the general public – is "worth a great deal". Holidaymakers for example can also do their bit, by not bringing fruit back with them from far-flung corners of the world, by cleaning their shoes before embarking on their return journey, and by ensuring that fishing equipment is spick and span before they head for home. And definitely by not simply releasing unwanted exotic pets into the wild.


Senckenberg Biodiversity and Climate Research Centre (BiK-F)

An interdisciplinary team of 130 scientists at the Senckenberg Biodiversity and Climate Research Centre (BiK-F) studies the numerous interactions between biodiversity and climate. In their work they use methods from all kinds of different disciplines, ranging from molecular genetics to satellite-based remote sensing of climate.