The Thorny Challenge Facing East Africa’s Ecosystems
Invasive species are a major threat to global biodiversity and rank among the leading causes of species extinction worldwide. They disrupt ecosystems by outcompeting native species for resources and altering habitats, leading to serious consequences for wildlife and communities. One such invasive species wreaking havoc in East Africa is Prosopis juliflora, locally known as Mathenge or Biskuti mjinga
Originally from tropical America, Prosopis was introduced to Kenya during the 1980s and early 1990s as a solution for restoring arid lands. The tree's ability to grow quickly and withstand drought made it appealing for afforestation projects. Unfortunately, heavy rains during the 1997-1998 El Niño event and livestock transporting its seeds spread Prosopis beyond its intended areas.
Prosopis has transformed from a helpful tree into a serious problem for East Africa. Its rapid growth reduces biodiversity by choking out native plants and depleting water resources—each tree consumes about 36 litres of water daily. This overconsumption leads to drying boreholes and wells, which are vital for local communities.
Moreover, Prosopis poses health risks. Its sharp thorns can injure wildlife, as seen at Lake Bogoria, where birds often become trapped when landing and die. The tree also creates stagnant water pools that attract mosquitoes, increasing the risk of malaria in surrounding areas and if causes injuries that take time to heal if you get pierced by the thorns
The economic consequences are equally concerning. Many pastoral communities who rely on grazing lands for their livestock face significant losses due to the invasion. As Prosopis takes over, it alters river courses, limits access to water and shifts livelihoods from farming to wood harvesting.
To combat these challenges, the Woody Weeds (WW+) project was launched in 2021. This initiative operates in Kenya (specifically in Tana River, Isiolo, and Baringo counties), Tanzania, and Ethiopia. It aims to manage the spread of Prosopis, supporting Kenya’s national strategy to mitigate its negative effects on ecosystems and communities.
Prosopis juliflora. Photo: Nyatichi Beverline / CETRAD
CETRAD has played a significant role in the WW+ project, particularly in Isiolo. Some key achievements so far include:
The project focuses on educating people about the impacts of Prosopis and securing long-term funding for its management. Working with various partners such as CABI, Kenya Forestry Research Institute, University of Nairobi, and CDE Bern, CETRAD contributes to restoring and managing rangelands in Kenya’s arid and semi-arid regions.
In Isiolo, a strategic removal process is underway to manage Prosopis along the riverbanks. This involves cutting the trees, clearing surrounding vegetation, and digging around the roots to prevent regrowth. Finally, the trees are burned with dry cow dung to ensure they do not return. In addition to these physical methods, chemical and biological strategies, such as introducing natural predators, are being explored.
The invasion of Prosopis presents a formidable challenge, but initiatives like the WW+ project offer hope. By combining scientific knowledge with community efforts, we can manage invasive species and restore balance to our ecosystems. The ongoing work along the Isiolo River exemplifies the dedication to creating healthier environments for all. As we tackle this issue, it is vital to remain committed to safeguarding our natural heritage for future generations.