Plant Invasions in Africa

This chapter reviews the current status of invasions of non-native plants in Africa. It draws on the most comprehensive global database of naturalized plant species (GloNAF) to provide a quantitative assessment of the distribution of naturalized plants across the continent. South Africa has the greatest number of naturalized plant species of any African country (1139), and another 7 countries have more than 300 naturalized species. The number of naturalized plant species is strongly positively correlated with native plant species richness. Equatorial regions harbour fewer naturalized species than temperate regions, and regions with Mediterranean-type climate have more naturalized species than tropical and subtropi-cal regions. Patterns for naturalized species from GloNAF do not reflect the distribution of non-native species that invade and transform natural and semi-natural ecosystems. Quantitative data on such invasive species were available only for South Africa. The situation for the whole continent was assessed using published and unpublished resources, the experience of the authors and correspondence with regional experts. Distribution patterns are discussed, a preliminary list of the 20 most widespread and impactful invaders of natural ecosystems was compiled, and information was collated on their impacts and the attempts to manage these invasions. Many invasive plants have substantial impacts on biodiversity and ecosystem services and have major negative effects on human livelihoods. Such impacts have only been quantified for a handful of species and a few regions. South Africa is the only African country that has invested in substantial and systematic efforts to manage plant invasions. Examples of approaches for managing plant invasions and the barriers to success are discussed. There is an urgent need for standardized assessments of the extent and impacts of plant invasions across Africa. Such information is crucial for informing policy and justifying the allocation of resources to management. Suggestions are provided on key changes needed to improve the effectiveness of management of plant invasions at the regional level in Africa.