Challenges of Invasive Mathenge Trees in Samburu County

John Rumakato, a resident of Lerata at the base of Mount Orolokwe in northern Kenya’s Samburu County, recalls a time when the landscape was different. “This used to be a treeless expanse, where grass thrived everywhere, and livestock wandered freely,” he shares.

Unfortunately, about three years ago, Rumakato faced a devastating loss—193 of his cattle perished while searching for grazing land that’s increasingly contested by both Indigenous herders and commercial ranchers in Laikipia’s conservation zones. “Some of my cows were shot,” he recounts, “and people were killed too.” Out of a herd of 200, only seven remain.

A significant issue driving his livestock into conservation areas? The spread of the mesquite shrub, known locally as “Mathematics” (scientifically as neltuma juliflora, previously prosopis juliflora). The introduction of this plant, originally from South America, occurred in 1948, and by the 1970s, it had proliferated across East Africa.

Initially, it was viewed as a solution against desertification, helping to prevent soil erosion and providing resources like fuel and animal feed. However, as it spread, it morphed into a major problem. This invasive shrub is now recognized as one of the world’s worst invasive species.

Mathenge has taken over much of Kenya, dominating approximately 2 million hectares. It flourishes in arid regions, choking out natural pastures and extracting vital moisture from the soil.

“There’s no way to eliminate these plants, so we need to control it,” states Ramadan Gorilla, an environmental officer, acknowledging the plant’s rapid encroachment.

In 2006, residents of Baringo, a region severely impacted by Mathenge, filed a lawsuit against the Kenyan government for damages caused by the tree. The court ruled against the government.

Davis Ikirol, a director from Kenya Somalia, mentions that the shrub’s rapid spread has led to blockages in waterways, resulting in community evacuations, school closures, and disruptions to river flows.

In Samburu County, where over 60% of residents rely primarily on livestock, the situation is dire. Many animals die from Mathenge’s toxicity after consuming it, while its sharp thorns can injure livestock. Even its sweet pods, though seemingly harmless, cause dental issues and tooth loss.

Livestock inadvertently contribute to the shrub’s spread by consuming its pods and dispersing seeds through their waste.

In response to its harmful impact, the Kenyan government classified Mathenge as a harmful weed in 2008 and mandated its eradication where feasible. Yet, as officials note, complete elimination isn’t realistic.

Some initiatives are exploring the possibility of turning Mathenge into a resource. By creating products from it, communities hope to mitigate its growth. One such project, involving VSF Suisse and the University of Nairobi, has taught locals like Rumakato how to utilize the shrub to their advantage. “We found ways to harness its potential,” he explains.

A method includes transforming the pods into animal feed by combining them with other materials like straw and bean husks, thus enabling livestock support during droughts when food is scarce.

Efforts are being made to refine the feed to ensure it’s nutritious and easy for animals to digest, ultimately aiming to reduce sugar content while also curtailing the plant’s expansion.

Additionally, training sessions on producing briquettes from Mathenge wood offer an alternative energy source, easing demand on natural trees, particularly in areas reliant on charcoal for cooking.

However, a significant effort is still needed to curb the shrub’s invasive nature. Its roots can penetrate up to 35 meters into the ground, consuming crucial water resources.

The dense thickets formed by Mathenge alter water courses, causing flooding in some regions, such as Isiolo, leading to complete community relocations.

The ongoing water stagnation also favors the breeding of disease-carrying mosquitoes, raising concerns about malaria and other illnesses.

This crisis extends to broader biodiversity challenges. “When Mathenge grows freely, little else can thrive beneath it,” concludes Douglas Machuchu, project manager at VSF Suisse, emphasizing the urgent need for control measures.