This paper briefly discusses the introduction of Prosopis species into Africa from their native America over the past 200 years. Although some are useful for fuel, fodder or erosion control, others have become invasive weeds. The first detailed study on the impacts (both positive and negative) of invasive Prosopis in Africa was carried out in Kenya in 2002. This gave monetary values to the smallest of impacts, including costs of repairing bicycle tires and fishing nets damaged by thorns and income from sale of firewood, and also noted peripheral effects, including the 7% of respondents who stated that Prosopis thickets were a refuge for thieves. The conclusion was that, at present, the positive benefits outweigh the negative costs, but this balance was shifting in favour of the negative as invasion continues and ecologically sensitive areas are increasingly threatened. A change in policy is recommended to improve management and utilization of this potentially very valuable resource.
Pasiecznik, N. The good, the bad and the thorny: impacts of Prosopis in Africa. CABI, Wallingford, UK (2004)