The global movement of goods and people, in its modern form, has many unwanted side effects. One of these is that animal and plant species travel around the world with it. Often they fail to establish themselves in the ecosystems of the destination areas. Sometimes, however, due to a lack of effective management, they multiply to such an extent in the new environment that they become a threat to the entire ecosystem and economy. Thousands of alien species are currently documented worldwide. A quarter of them are in highly vulnerable, aquatic habitats.
