Calls to eliminate ‘mathenge,’ Prosopis juliflora as control strategies fail in Kenya

By Gatonye Gathura

Kenya does not have the technology, money or the will to stop Prosopis juliflora from replacing 19 million people in arid counties and 90 percent of wildlife.

Current efforts to turn the invading weed into human food, animal feed, furniture or charcoal have failed to stop or check its catastrophic spread.

“Although the management of prosopis by utilization has been promoted for 10–15 years, its spread has neither stopped nor slowed down,” reports the Kenya Forestry Research Institute (KEFRI) in a recent study.

Scientists now suggest the ideal thing is to eradicate the weed, but the technology to do so, or the US$1.6 billion required for elimination are not available.

Catastrophe

The other alternative, scientists indicate is to kick the can down the road and possibly postpone an inevitable catastrophe.

With or without the current control measures, scientists estimate the plant could take over 80 percent of arid lands replacing about 19 million people, 70 percent of livestock and 90 percent of Kenya’s wildlife.

Until now the government through KEFRI, has been advocating for its utilization but new evidence shows this has failed to stop the weed.

Purity Rima Mbaabu of the University of Nairobi and lead author in the KEFRI study says in Baringo County alone the weed increased by 2,031 percent in 28 years.

“The shrub expanded from 882 hectares in 1988 to 18,792 hectares in 2016,” said Mbaabu. The study was published in May 2019 in the journal Remote Sensing.

During the same period, Mbaabu says grasslands in Baringo County declined by 86 percent, irrigated cropland by 57 percent, and rain-fed cropland by 37 percent, a third of the shrinkage due to prosopis.

First admission

This is the first time the government has publicly admitted current initiatives to stop the weed are not working.

In June residents and leaders in Tana River County told Environment Cabinet Secretary Keriako Tobiko they want the weed eradicated from the area.

Similar demands have been made in Garissa, Coast as well as Kajiado, areas where residents claim the weed is a threat to their survival.

In Kajiado, the County Assembly has initiated a legislative process for the eradication of prosopis.

“This weed is causing much harm to locals and needs to be eradicated,” said Diana Mepukori, the Vice-Chairperson Committee on Agriculture, Livestock and Fisheries.

An earlier study by the National Museums of Kenya reported: “An overwhelming majority of residents in all study sites, 64 percent in Garissa, 78.6 percent in Turkana and 67 percent in Baringo said life would be better off without prosopis.”

Stop the spread

“We have several prosopis management technologies but nothing to stop its spread,” said KEFRI personnel at Kabarnet Agriculture Show held in September.

At the show, KEFRI was demonstrating various products from the shrub including poles, timber, and furniture, animal feed, ‘chapatis, mandazis’ and cakes.

“The cakes and mandazis are still experimental and not yet introduced to the public,” said Peter Korir of KEFRI. Uptake of prosopis animal feed was described as extremely low.

Korir said KEFRI is working with the Centre for Agriculture and Bioscience International (CABI) on a chemical eradication technology.

“This is still under experimentation being assessed for efficacy and environmental impacts before use.”

An earlier study by the National Museums of Kenya was more forthcoming on the prosopis crisis facing the country.

It warned that unless eradicated, prosopis could in a few decades overrun 29 arid and semi-arid counties threatening the livelihoods of about 19 million residents.

Threat to national parks

“The current trend indicates prosopis will overwhelm key livestock, farming, tourism and biodiversity-rich habitats in infested arid areas,” said lead author Patrick Maundu.

Crucial areas already under threat include Lotikipi plains – an important grazing area for the Turkana community, Turkwel river valley, Tsavo National Park, Tana River Primate National Reserve and Arawale National Reserve.

Other conservation areas affected include; Lake Bogoria National Reserve, Shaba National Reserve, Samburu National Reserve and Marsabit National Reserve as well as Mt. Kulal Biosphere Reserve.

The weed is also a threat to Tsavo, Amboseli and Maasai Mara wildlife sanctuaries.

The report had blamed government agencies for promoting alternative use of prosopis rather than working on eradication since ‘its negatives are known to far outweigh the positives.’

Eradication

An eradication process would involve clearing the weed from all infested areas. Cleared land would then be monitored, and new plants continuously removed for up to 20 years.

On average, the Maundu team estimated it would cost about US$1,600 to mechanically clear the weed from one hectare of land.

This roughly translates to about US$ 1.6 billion to clear the estimated one million hectares under prosopis countrywide – an almost impossible expenditure to secure.

But all may not be lost though, says Mbaabu, if the current technologies including chemical, biological or physical removal are integrated and well-coordinated.

 (Article prepared with support from the African Academy of Sciences)

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