Insiduous Weed Chokes Rangelands in East Africa

East Africa's priceless rangelands for years have struggled against degradation caused by overgrazing and soil-depleting crop farming. Now ecologists are coming to grips with a third villain: the leleshwa weed, a fast-growing, tough-to-control shrub that is overtaking large sections of grassland.

The plant (Tarchonantus camphoratus), known by its Masai name leleshwa, has few redeeming features--it chokes off other plants and is not consumed by domestic or wild animals. "The shrub is highly adaptive to range soils," said a recent report in the Kenya newspaper the East African, "including hostile substrata like rocky cliffs, where it grows in multiple stems forming tough root networks that render the soil poorer and unsuitable for other species, especially grasses and herbs."

Ecologists say the leleshwa weed has grown fourfold over the last 30 years; by 1996 it covered an estimated 4,800 square miles in Kenya, mainly in the Rift Valley. In Laikipia, a region in north central Kenya that AWF has designated as an African Heartland, the spread of the shrub has forced wildlife to the edges of protected areas, heightening conflicts with livestock owners as the animals compete for food. A trust land between Naivasha and Gilgil, the East African reported, has turned into a virtual leleshwa forest, and its wildlife has disappeared.

Some ecologists have said if the weed is not controlled, some of East Africa's savannas could become barren deserts. AWF's Conservation, Economics and Commerce program is exploring one solution: It is working with ranches in Laikipia to assess possible commercialization of leleshwa oil.