The non-indigenous species do not only constitute a huge problem for the Mediterranean, but also for the European rivers and lakes, according to a European study with the participation of Greece.
Over 755 alien species have invaded the waters of the European continent. The number has increased substantially in the last 60 years as a result of the globalization.
Researchers have found that four countries (Germany, Britain, Italy and Russia) are the main entrance gates of the exotic species to European fresh waters. Germany, a country with huge lakes and rivers, has collaborated to the import of the most alien species in Europe.
The nuisance species, fishes and other marine organisms usually come from aquaculture plants where they have escaped from or, from the freeing of fishes that were kept in domestic aquariums as pets.
The transport of non-indigenous species by ships that cross canals and sail in the European rivers also plays a significant role. The European waterways net exceeds 28,000 km. As new canals are being constructed and the old ones are being modernized, the invasion of alien species will further increase in the future. The climate change will also intensify the problem because the European freshwaters will become even hotter and therefore friendly to the exotic species.
Researchers noted that the European marine ecosystems suffer from the highest loss of diversity in comparison with most of the ecosystems of the land. The invaders are responsible for 20 percent of the domestic marine species that disappear from the European rivers and lakes.
Therefore, scientists recommend immediate and intensive action to lessen the negative effects.