The impact and control of alien aquatic vegetation in South African aquatic ecosystems
Water hyacinth, water lettuce, salvinia, parrot's feather and red water fern are South American aquatic plant species that have become invasive in aquatic ecosystems in South Africa. The lack of indigenous natural enemies and the presence of nutrient rich waters have contributed to their invasiveness. The impacts of dense mats of these weeds include the reduction in quality and quantity of water for urban, agricultural and industrial uses, an increase in siltation of rivers, dams and wetlands, a reduction in water surface area for recreation, clogging of irrigation canals and pumps, drowning of livestock and severe deterioration of aquatic biodiversity. Biological control offers a sustainable management tool for all five species and significant success has been achieved in the control of these weeds. However, the long-term management of alien aquatic vegetation relies on the prevention of other species entering South Africa and, more importantly, the reduction of nutrients entering aquatic ecosystems.