The spread of Prosopis juliflora must be controlled to ensure food security for AfricaCredit: Forest and Kim Starr/CC BY 3.0 US
The resilient and adaptable mesquite tree, was introduced to East Africa to provide foliage, fuel, and animal fodder in arid areas. In the 1970s and 1980s the evergreen Prosopis juliflora, native to South America, became even more important to the region to increase forest cover to help combat the effects of climate change.
However, the plant became invasive and started wreaking havoc in many African countries, including Ethiopia, Kenya, Tanzania, Sudan and Ethiopia. From losses in biodiversity, to spreading malaria, the plant’s ill effects outweighed its expected benefits. The mesquite is now listed by the International Union for Conservation of Nature among the world’s top 100 worst invasive alien species.
Impact on local ecosystems
The mesquite has overrun local species and over-used water, causing a loss of biodiversity, and imbalances in local ecosystems, which led to land degradation and soil erosion. The fast-growing and spreading species, with research estimating that one tree can produce between 630,000 and 980,000 seeds in a year.
Tobias Landmann, an expert in geospatial science from the International Center of Insect Physiology and Ecology in Nairobi, explains that the dense canopy and shaded areas provided by the mesquite are an ideal microhabitat for resting and nesting for species like adult mosquitoes. The flowering branches of the mesquite also provide a source of sugar, which is necessary for mosquito survival.
“Compared to areas with local indigenous plants, we observed that areas under invasive plants may have higher vector loads and provide a higher risk to humans,” says Landmann.
Of the 247 million cases of malaria worldwide in 2021, 95% were in Africa, causing 590,000 deaths.
The mesquite’s rapid growth overshadows native and more nutritious grasses used to feed animals, hurting the livelihood of nomadic pastoralists.
Elizabeth Lotira, a small-scale farmer in Turkana, Kenya, witnessed the devastating effects of the mesquite tree, locally known as mathenge. She recalls the plant’s rampant growth in her village, making it almost impossible to access farms and a nearby river, where the community fetches water for domestic use.
“When the shrubs got to my farm, I began to uproot them physically. Desperate, I began to burn the bushes but I got overwhelmed…as new plants were sprouting daily,” Lotira recounts. “Within a few weeks, I could not cultivate and grow vegetables, oranges or anything.”
According to Lotira, the lack of usable farmland meant many families were unable to afford two meals a day, leading to growing malnutrition rates.
Finding solutions
The Kenyan government and Mercy Corps, an NGO, are partnering with pastoralist communities to develop and advocate for sustainable land management practices that mitigate the impacts of the mesquite invasion and resulting malnutrition. These practices include rotational grazing and physical removal of the trees.
“Our results illustrate how combined management and restoration interventions can result in grassland vegetation within a few years,” said Stanley Mutuma, climate-smart agriculture advisor at Mercy Corps Kenya.
Pastoral communities in northern Kenya are determined to return lands to thriving agricultural zones, and are taking part in a five-year USAID initiative for resilience and food security, called Nawiri, implemented by Mercy Corps.
Lotira says the use of machinery in the removal of mesquite, under the Nawiri programme, was necessary because the physical effort needed to uprooting the trees thwarts control efforts. The pastoralists also collect pods to limit new seedlings.
The Nawiri program has helped the Turkana pastoral communities reclaim 3,000 acres of lands into thriving agricultural zones in eight years. The initiative is targeting to reclaim 10,000 acres in Turkana by 2027, and has an broader goal of sustainably reducing levels of persistent acute malnutrition in Kenya and semi-arid lands of Turkana and Samburu.
“These lands are now providing a much-needed source of food and income for local communities,” says Mutuma. Lotira says she is now planting vegetables, pawpaw and mango trees that give her yields for her household consumption and sale.
Although programmes like Nawiri are helping reclaim lands affected by mesquite, Mutuma and other scientists believe that more research is needed to curb the plant’s effects, as well studies into the possibility of converting the evergreen protein-rich pods into animal feed.
