From first reports to successful control: a plea for improved management of alien aquatic plant species in Germany

摘要

Alien aquatic plant species can strongly affect all types of freshwater ecosystems. Their number has more than doubled between 1980 and 2009 in Germany, and currently 27 are known and their number is still increasing. Eleven have been classified as invasive, but only four are managed yet, mainly by weed cutting. Most of the alien aquatic plant species were probably introduced as aquarium and pond waste. Despite this fact, 18 of the 27 known alien species are traded as ornamentals for aquaria or garden ponds in German shops. Alien species can most successfully be controlled when their management starts as soon as possible after their introduction. In Germany, the delay between first records and start of management actions seems too long for successful control. The public awareness of alien aquatic plants and problems they can cause in Germany is still limited despite a number of recent projects. At present, Black lists are developed that help nature conservationists, stakeholders and politicians to select those alien species for which prevention measures should be implemented. These, however, are not legally binding and laws regulating trade in Black listed plant species are strongly needed to reduce their impact on the environment and economy.