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Quick review of current activities to prevent and control invasive species in Africa.

Geoffrey Howard
(IUCN Invasive Species Coordinator, Global Species Programme)

additional contribution:

Jean-Marc Garreau
(Regional Programme Coordinator of IUCN West Africa)

(This is necessarily a brief summary so apologies in advance to those whose important activities have not been mentioned).

Africa is increasingly invaded by all manner of organisms with increasing threats to biodiversity, development and human health. This is exacerbated by more than 40 continental countries, each with many neighbours, “porous” borders and limited capacity to address biological invasions. The fastest spreading invasive species are alien herbs and shrubs that have only been in Africa for a decade or two; there are also some species of trees (and a notable alien shrub, Lantana camara) which were brought into Africa more than 50 or 100 years ago for various purposes which are now becoming invasive in forest, woodland and even grassland situations. Four main alien invasive floating weeds are now present in most freshwater systems: Eichhornia crassipes, Salvinia molesta, Pistia stratiotes and Azolla filiculoides (while A. pinnata var africana is also becoming troublesome). The first three respond well to bio-control agents while the azollas, which are much more recent invaders, have avoided effective prevention and control in most tropical countries. All of the African island states are particularly prone to alien plant invasions; some, such as Seychelles, take this very seriously and are preparing national strategies to address the problem. A particular threat to aquatic and semi-aquatic biodiversity is the spread of both alien freshwater crayfish (there are no native freshwater crayfish on continental Africa) and locally alien species of fish for aquaculture.

Africa-wide, the Environmental Action Plans of NEPAD (the New Partnership for Africa’s Development) include significant efforts to prevent and manage their biological invasions as do the Sub-Regional Environment Action Plans in Southern, Eastern, Central, West and North Africa. Some have been activated while others await funding. A 4-country project to develop capacity for addressing invasions by alien plants is in its fourth year in four countries representative of 4 of the sub-regions – Ghana (representing West Africa), Ethiopia (for Eastern Africa and Horn of Africa [IGAD]), Uganda (East Africa, EAC) and Zambia (Southern Africa, SADC). These 4 countries are developing national strategies based on real-time experiences with experiences of trying to manage field sites of plant invasions – which will be relevant across the four sub-regions. At both extremities of Africa, Egypt and South Africa have the most-developed biosecurity systems and national IAS strategies; Egypt is currently reviewing its strategy while South Africa is developing fresh policies and laws to prevent and manage all types of biological invasions. Senegal is committing important funds for mechanical eradication of Typha spp. in river Senegal.

An interesting (and at times emotive) debate is current in many parts of Africa concerning the risks of introduced feedstocks for biofuel plantations across the continent becoming invasive. Another refers to the spread of Prosopis spp. (mainly P. juliflora) in many dryland areas and whether current emphasis should be on reduction of spread and possible eradication of some invasions or alternative management through utilization of this invasive plant. Several countries in West Africa currently struggle with serious invasions of the native species of Typha spp. reeds in places where water management has changed freshwater systems such that typha can spread unabated. In Eastern/Southern Africa the management authorities of the three great lakes (Victoria, Tanganyika and Malawi/Nyassa) are faced with increasing evidence of invasions by plants and fish and are beginning to balance fisheries production with biodiversity conservation.

Alien Lantana camara invading the “rain forest” maintained by the spray from Victoria Falls in Mosi-oa-Tunya National Park and World Heritage Site, Zambia. This tropical American shrub is still spreading across Africa and, here at the falls, is being managed by physical clearing and very cautious herbicide application.   Alien invasive Azolla filiculoides completely covering the surface of a water storage and livestock water dam in East Africa: this plant prevents the growth of all other freshwater vegetation and aquatic fauna in such situations and can seriously affect livestock that drink from invaded waters.