allAfrica.com has this very interesting article about the consequences of the introduction of mesquite (Prosopis juliflora) to Kenya. It seems that the National Environmental Management Authority of Kenya has called upon the FAO to answer for their intentional introduction of this noxious weed. Mesquite is often grown as a source of wood (firewood and woodcraft), to combat soil erosion, to amerliorate sites by fixing nitrogen, and even as a food source (the pods). The Community Museums of Kenya is claiming that parts of the country now suffer from low water tables, decreasing biodiversity, and even more soil erosion, all due to mesquite. Bonus points to allAfrica.com for using the plant's scientific name.
Thanks to a member of the ALIENS-L listserver for posting a link to the story.