Fighting invasion with coffee and rusks
● Chainsaws, herbicides and hungry bugs are the usual weapons in the war against alien invaders — but now baristas, foodies and health nuts have joined the ranks.
Their target is the mesquite plant — an umbrella name for several species of the Prosopis genus — which researchers say already covers 6-million to 8-million hectares in South Africa and could eventually infest about 56-million hectares.
Curbing it is a daunting challenge, but Brandt Coetzee is among those making it possible for people around the world to eat and drink the problem; his Somerset West company Dune Foods is roasting mesquite seeds and pods into a caffeine-free coffee substitute and grinding them into a powder with a range of reputed health benefits.
And consumers of the products will be helping to provide an income for hundreds of people in the Northern Cape who harvest the pods of the tree — commonly known as the Suidwesdoring because it also thrives in Namibia — every summer.
“We see it as a way to create jobs, as an income stream for farmers, a way to prevent new trees growing, to get pods into the market because of the health aspects ... So it’ sa win-win for everyone,” said Coetzee, who calls his coffee-like product MannaBrew.
“The more product we move, the more casual labourers we employ. We employed 690 in Calvinia, in Prieska it was just over 1,000 — we can employ a few thousand people in the Northern Cape, which has the worst unemployment in South Africa.”
Mesquite, indigenous to the arid zones of the Americas, was introduced into South Africa in the 1890s to provide shade and animal feed in the form of its pods. But it proved too successful and now forms dense stands that can be impenetrable to humans or livestock, drains scarce underground water and drives out indigenous species.
“It’s a huge issue,” said Ross Shackleton, a researcher with the centre for invasion biology at the University of Stellenbosch. “It’s starting to spread into the Western Cape, the Free State. It’s impacting underground water resources.”
Its roots are among the deepest of any species in the world, in some cases penetrating to 50m or more.
“It is the second most widespread invasive tree genus in the country after wattles,” Shackleton said. “There are huge impacts on biodiversity and ecosystem service — especially water supply and grazing potential — which translate to impacts on local economies and livelihoods.”
Philip Ivey, a researcher at the centre for biological control at Rhodes University, is encouraging an integrated effort to fight the invasion on various fronts. The anti-mesquite coalition brings together Dune Foods, Working for Water, landowners, engineers who are incorporating mesquite wood chips into an innovative building material — and various insects.
Ivey said the first “biocontrol” insect introduced, in the late 1980s, was one that eats only the dry seed of mesquite. It is still having an impact, he said, but the invasion continues due to “the very high seed production of the plants”.
In recent years more insects were released — the green podlet weevil, which feeds on green seeds in developing pods, and the leaf-tying moth, which can damage whole trees by eating the leaves, Ivey said.
“There are anecdotal reports that the moth is spreading quite fast,” he said. “More funding is needed to support ongoing biological control efforts, but biocontrol won’t destroy Prosopis, it’s only going to reduce density and spread. You’re still going to have to find ways to use the biomass and pods.”
This year the Institute of Culinary Arts (ICA) in Stellenbosch did just that, developing recipes that use MannaBrew and mesquite flour. Third-year students came up with baked goods, savoury dishes and coffee-flavoured liqueurs and brandies, said ICA product development lecturer Ankia Venter.
“You would use the coffee in a baked product or a cooked product, it really enhances some of the flavours,” she said. “It pairs nicely with something like chocolate or it gives you a deep earthy flavour to complement or accompany meaty flavours like mushroom, beetroot, meat.
“With the mesquite powder there’s no flavour as such, only an influence on texture and colour, so it bakes darker. And then it gives you the health benefits,” Venter said.
Coetzee said “the magic of mesquite” was that in its powdered form it lowered the glycaemic index (GI) of baked goods “by up to 40%”.
“You only need to include 2g or 4g of mesquite powder in a recipe to help to reduce the GI. That’s excellent news because now you can take, say an oat cookie, or any other biscuit — the moment you add mesquite to that then it’s suitable for a diabetic.”
Other medical applications of nutrientrich mesquite include treating sports muscle injuries, according to research by the University of Stellenbosch and the South African Medical Research Council.
“It gives you a lot of endurance energy,” said Coetzee. “We’ve got a shake on the market, the old cyclists, about 60, they use that shake and perform better than young guys. [Mesquite] is an exceptional product and I see myself just as the custodian of this, it’s something the Lord gave us and we need to tell the world about it.”
Coetzee grew up in Prieska, at mesquite ground zero, and has been working on ways to control its spread for 27 years.
“If you look at that one 225g packet of MannaBrew ... conservatively, the amount of seeds in one packet saves nature about 8million litres of water per annum. That’s the number of trees we prevent from germinating.”
Dune Foods is now buying about 50t of pods every year, but Coetzee acknowledges that doesn’t make more than a dent in the problem.
“There are some farms in the Vanwyksvlei area where farmers have to leave their farms because of the invasion of these trees.”