For millions of people across Southern Africa, the humble mopane worm represents more than just food – it’s a lifeline. These protein-rich caterpillars, scientifically known as Gonimbrasia belina, have sustained communities for generations and, according to recent studies, mopane worms now generate trade value exceeding US$85 million annually. But groundbreaking new research suggests this vital resource may be in serious trouble.

By Maile Matsimela, Digital Editor at African Farming

A team of international scientists led by Zwannda Nethavhani from Stellenbosch University, along with colleagues Ruan Veldtman, Casper Nyamukondiwa, William Versfeld and Barbara van Asch from institutions across South Africa, Botswana and Namibia, embarked on the first comprehensive genetic study of mopane worm populations. Their goal was ambitious: to understand whether these insects can survive the increasing pressures they face from climate change, habitat destruction and intensive harvesting.

“We wanted to perform the first baseline genetic assessment of Gonimbrasia belina by analysing their genetic diversity, phylogeographical structure and demographic history,” the researchers explained in their study published in a leading scientific journal.

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What Makes Mopane Worms So Important?

Before diving into the findings, it’s worth understanding why these caterpillars matter so much. Mopane worms are the larvae of a large moth that feeds exclusively on mopane trees found throughout Southern Africa’s woodlands. As the researchers note, “They are an important traditional food source [that’s] rich in protein, iron, calcium and other nutrients.”

But their importance goes beyond nutrition. For rural communities, mopane worms provide crucial income during harvesting seasons. The researchers highlight the dramatic growth in economic value, noting that although “in 2014, the cross-border trade of mopane worms between Botswana, South Africa and Zimbabwe was valued at US$4 million to US$6 million”, recent studies show that this has grown significantly. The insects also play a vital ecological role, contributing to “nutrient cycling within mopane woodlands and influencing woodland ecosystem dynamics”.

Mopane Worms. Photo: John Mendelsohn — Mopane worms. Photo: John Mendelsohn

The Research Approach

Between 2017 and 2022, the research team collected samples from 24 sites across South Africa, Botswana and Namibia. Using advanced genetic analysis techniques, including DNA sequencing and cutting-edge genomic tools, they could trace the genetic “fingerprint” of different mopane worm populations.

Think of it like a massive family tree: the scientists could see how closely related different populations were and whether they were healthy enough to survive in the long term.

The results paint a concerning picture, as researchers found that “Gonimbrasia belina shows strong phylogeographical structure at a broad scale, with distinct genetic clusters separating Namibia from the Limpopo River Basin”.

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In simpler terms, mopane worm populations have become isolated from each other, like islands in an ocean. This isolation is dangerous because it reduces genetic diversity, which is the natural variation that helps species adapt and survive environmental changes.

The findings were particularly troubling for certain regions. “Genetic diversity is highest in South Africa, followed by Namibia, and lowest in Botswana,” the study revealed. Even more concerning, the researchers found “evidence of recent bottlenecks, population contraction and small effective population sizes” in both Botswana and South Africa.

A population bottleneck is like squeezing a wide river through a narrow pipe – only a few individuals survive to reproduce, dramatically reducing the genetic health of future generations.

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What this Means for the Future

The implications are serious. As the researchers conclude, their findings justify “concerns over the sustainability of the species” and suggest that “the expansion of mopane worm trade and habitat destruction likely exacerbate population declines and genetic isolation”.

This genetic fragmentation means that even if mopane worm numbers appear stable in some areas, the underlying genetic health of the populations may be compromised, making them vulnerable to environmental changes, diseases or further habitat loss.

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A Call to Action

The research team doesn’t just highlight problems, it offers solutions too. It emphasises that “preserving mopane woodlands and implementing conservation-focused management strategies are critical to mitigating the decline of this economically and nutritionally important species”.

Their recommendations include:

Genetic monitoring programmes to track population health;
Conservation interventions to protect existing habitats;
Sustainable harvesting practices; and
Habitat restoration in genetically depleted areas.

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This groundbreaking research provides the first scientific baseline for understanding mopane worm genetics across their range. As the authors note, their work can “assist in creating informed management strategies for sustainable harvesting, habitat protection and the restoration of genetically depleted populations”.

The study, titled “Multimarker genetic analyses of Gonimbrasia belina, the most harvested wild edible insect of mopane woodlands in Southern Africa, supports concerns over the sustainability of the species”, represents a crucial first step in protecting this vital resource for communities across the region.

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