Namibia is affected by the invasion of alien invasive and indigenous encroacher species, of which some of these species covers hectares of land, stated to be encroached. Encroacher and invasive species are common terms used interchangeably although both contribute to bush encroachment they do not have the same meaning.
The term invasive is used to describe organisms that spread quickly and are considered as harmful species to the environment. Invader species are often considered a problem as they tend to alter ecological relationships among other species and can affect economic value of ecosystems. South Africa has implemented program called WfW (Working for Water) for removing alien invasive in a sustainable way. Alien invasive is a threat to biodiversity, water security and land productivity.
The most widely spread and dangerous alien invasive in Namibia is Prosopis glandulosa. Prosopis is mainly confined to riverbeds and adjacent areas where they tend to outnumber and eliminate other indigenous species reducing ephemeral flow in river beds through abstraction of ground water. Despite the impacts this specie can be used for nutritious fodder and fire wood. Read more on Prosopis distribution and impacts in Namibia in the SEAI study (pg.8).