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Background: Aquatic ecosystems in South Africa are prone to invasion by several invasive alien aquatic weeds, most notably, Eichhornia crassipes (Mart.) Solms-Laub. (Pontederiaceae) (water hyacinth); Pistia stratiotes L. (Araceae) (water lettuce); Salvinia molesta D.S. Mitch. (Salviniaceae) (salvinia); Myriophyllum aquaticum (Vell. Conc.) Verd. (parrot's feather); and Azolla filiculoides Lam. (Azollaceae) (red water fern). Objective: We review the biological control programme on waterweeds in South Africa. Results: Our review shows significant reductions in the extent of invasions, and a return on biodiversity and socio-economic benefits through the use of this method. These studies provide justification for the control of widespread and emerging freshwater invasive alien aquatic weeds in South Africa. Conclusions: The long-term management of alien aquatic vegetation relies on the correct implementation of biological control for those species already in the country and the prevention of other species entering South Africa. [ABSTRACT FROM AUTHOR]

A recent study shows that most aquatic alien plants in temperate cold climate are of tropical and subtropical origins and only those that can withstand cold climates become invasive. This suggests that a changing climate that becomes warmer may result in currently non-invasive alien plants becoming invasive in the future. To facilitate pre-emptive actions when controlling invasive aquatic plants in South Africa under climate change, we reconstructed predictive models for the five most damaging aquatic alien plants of freshwater systems in the country. We found evidence of contrasting shifts in species distribution ranges: the ranges of Myriophyllum aquaticum and Pistia stratiotes will contract, while Azolla filiculoides , Eichhornia crassipes , and Salvinia molesta will increase their future ranges with most suitable habitats found in the Western Cape province and along coastal areas. In addition, the predicted range contraction and expansion would result in some dams currently vulnerable to invasion becoming resilient while others that are currently resilient may become vulnerable due to climate change. These results can be used to develop future monitoring programs for aquatic ecosystems, prioritize control efforts, and raise public awareness on risks posed by these aquatic invasive plants, especially under future climate scenarios. [ABSTRACT FROM AUTHOR]