Farmers wage war on the invasive prickly pear as scientists and locals work to eradicate it with cactus-eating bugs and by turning it into biogas
Armed with rakes, hoes and machetes, a group of farmers hack at the spiky cactus plants sprouting all over their land, chopping them into pieces and carting them off in wheelbarrows.
In many parts of the world, the prickly pear, also known as opuntia, is used as natural fencing and decoration because of its flat, fleshy pads, colourful flowers and purple fruit.
But across Kenya’s arid northern areas, where grazing land has been depleted due to frequent droughts, the cactus has become a nightmare for cattle farmers and livestock herders.
Farmers at the communally managed Makurian Group Ranch in Laikipia County in Kenya’s Rift Valley say the non-native invasive plant destroys the grass their animals feed on, and can make the animals sick when they eat it.
“Despite our ruthless battle with opuntia, the cactus has made thousands of acres into a wasteland and won’t go away,” said Jackson Mukurinu, a farmer at the ranch who lost more than 800 goats and 85 cows after they ate the cactus.
Hoping to loosen the plant’s grip on grazing land, farmers, charities and scientists are working together to eradicate it using methods ranging from feeding it to insects to turning it into fuel.
The prickly pear was brought to the area by colonisers in the early 1900s, said Protas Osinga, a livestock officer in Laikipia.
Over time, a warming climate and rapid population growth had transformed it from a popular crop into an uncontrollable menace, he said.
During the droughts and prolonged dry spells that have become increasingly common in Kenya over the past decade, the cactus is often the only vegetation that thrives.
Livestock, birds, elephants and baboons often have no choice but to feed on the cactus and, when they do, they disperse its seeds as they move around the area. Meanwhile, Kenya’s expanding population has stoked demand for milk and meat, motivating farmers to add to their herds, which means even more animals spread the cactus seeds, Osinga said.
Highly resistant to drought and able to sprout from the smallest piece of root, the prickly pear grows aggressively and is remarkably difficult to remove, said Lerina Legei (80), an elder at the Makurian ranch.
Over the past five years, more than half of the approximately 1 200 farmers living in the area had been forced to move to other parts of the ranch after the cactus overran their land, he said.
Farmer Florence Kakweri (42) said: “Livestock is our livelihood, and opuntia – having no natural competition – has conquered the land by suffocating the native crops and leaving no grass for our livestock.”
She moved her family last year after the plant’s domination rendered them “helpless”.
Osinga, the livestock officer, said that about two-thirds of the ranch’s 6 640 hectares had so far been invaded by the prickly pear.
BLINDNESS AND INFECTION
The plant’s impact does not stop at killing pasture, said Richard Karmushu, the chairperson of the Makurian Group Ranch, it also exacerbates land erosion because animals looking for grass manoeuvre around the cactus and eventually carve deep paths into the soil.
Rain then washes away the weakened earth, resulting in deep gullies crisscrossing the farm.
When farmers remove the cactus, it leaves behind deep, bare patches that are prone to further degradation, Karmushu said.
Even worse, the plant’s effect on livestock is so devastating that Kenya’s cattle farmers have taken to calling it the “devil’s cactus”.
Ranchers at Makurian say their animals are often blinded by the plant’s sharp spines as they try to reach the grass growing underneath it.
And while humans and animals can safely eat the nutrient-rich prickly pear once its spines are removed, if ingested whole, the thorns can cause inflammation or infections that are sometimes fatal, said Osinga.
Simon Mbuki, programme manager for the aid agency World Vision, said tackling the cactus required a range of measures.
The charity is helping Kenyan pastoralists in four counties find ways to control the plant, he said. This is done by, for example, providing the tools the Makurian ranchers are using to cut away the plant from their land.
World Vision’s four-year project, which was launched last year, has so far managed to clear the cactus from 70ha, Mbuki said.
Because physically removing it can damage the soil, scientists have also been experimenting with a biological eradication method: tiny, cactus-eating insects.
Working with the Kenya Plant Health Inspectorate Services, pastoralists at Ol Jogi Ranch in northern Kenya have introduced millions of cochineal bugs – sap-sucking insects that feed only on cactus – to their land.
The ranchers reported that the bug, which is also commonly used to produce a red dye, can wipe an area clear of cactus while leaving the soil intact.
Some have also found ways to turn the nuisance plant into a money-maker by using it to create juice, wines, oils and biogas.
Environmental scientist Francis Merinyi, who grew up in Laikipia, started making biogas from prickly pears when looking for a sustainable way to eliminate the cactus.
Last year, he founded the company Cactigas to buy unwanted plants from farmers to turn into clean fuel.
The process involves chopping the cactus up into a paste that is diluted with water and left to ferment.
It eventually starts releasing methane and other gases, which are collected, purified and stored in tanks for heating and cooking.
“When you make biogas, you utilise the entire plant, which is not the case when making juice or wine,” said Merinyi.
The paste can also be used as organic fertiliser to add nutrients to land that has been degraded by a dry spell or a cactus invasion, he said.
STOPPING THE SPREAD
Njenga Kahiro, Laikipia County’s water and environment minister, said the local government was committed to helping farmers tackle the cactus.
Aside from supportive initiatives by charities and companies like Cactigas, the government is also working to persuade farmers to keep fewer animals and embrace zero grazing, which means feeding cows cut grass instead of putting them out to pasture.
Both methods help reduce the movement of cattle and curb the dispersal of the cactus, Kahiro said.
He added that officials were also training farmers to breed their own cochineal bugs to feed on the cactus.
At Makurian ranch, farmers are desperate for any method that will rid their land of the prickly pear and put a stop to the injuries farmers and their families sustain while uprooting it.
They hope it will be eradicated for good.
Caroline Wambui for the Thomson Reuters Foundation