This is big problem in the mainly arid Baringo County, in Kenya's Rift valley as well as other counties north, east and south of the country.
The guilty party is Prosopis , also known as Mesquite or 'Mathenge' (Kenya) or 'Promi' (Baringo). It is a thorny shrub or small tree native to Mexico, other South American countries and the Caribbean.It was introduced in Baringo in the 1980s as part of a project to prevent desertification and provide firewood and livestock fodder for local communities. It is deep-rooted, multi-stemmed and produces numerous highly nutritious pods with strongly embedded seeds.
The species is currently naturalised in parts of East Africa, South Africa, Asia and Australia. It provides wood, shade and helps to control soil erosion in degraded areas. Its fruits are used mainly as livestock fodder and occasionally for food.
Prosopis has no natural enemies in East Africa, such as herbivorous insects and plant pathogens. It has spread rapidly from the original plantations and invaded the surrounding natural grasslands, shrublands, and croplands.