A European study in which Greece participated found more than 755 alien species that have invaded the Mediterranean waters of the European continent. The non-indigenous species are a huge problem for the Mediterranean as well as for European rivers and lakes, say experts.

The number of alien species has increased substantially in the last 60 years as a result of the globalisation. Researchers have found that Germany, Britain, Italy and Russia are the four countries viewed as the main entrance gates of the exotic species to European fresh waters. Germany, a country with huge lakes and rivers, is viewed as responsible for the import of the most alien species in Europe.

The nuisance species and other marine organisms come mainly from aquaculture plants from where they have escaped or from the freeing of fish from domestic aquariums where the creatures were kept as pets. Non-indigenous species brought in by ships that cross canals and enter European rivers are also viewed as carriers of the creatures.

It is believed that alien species will increase the invasion of European waterways in the future. Climate change is also forecast as playing a role in the intensification of the problem because European freshwaters will become hotter and more friendly to exotic species. As a result, researchers believe that European marine ecosystems will suffer from the highest loss of diversity. Invaders are viewed as responsible for the disappearance of 20% of domestic marine species that disappear from European rivers and lakes.