Experts say the decline in the mopane worm harvest is having a serious effect on local communities that depend directly or indirectly on the industry.
According to Matomani, a South African company using mopane worms to provide sustainable, low-impact, organic, healthy and protein-rich dietary additions, the mopane forests are shrinking and as a result, the harvests of mopane worms have been decreasing and the local communities are suffering.
Caswell Munyai, a senior lecturer in invertebrate biology at the University of KwaZulu-Natal, said recent studies have shown that both the mopane worm (Gonimbrasia belina) and the tree species significantly affect the socio-economy of Southern Africa where they occur.
“The caterpillar has important nutritional content readily available to millions of people who are currently not meeting their daily nutritional requirements. The declining harvest and loss of mopane worms will negatively affect the trading of these caterpillars,” he said.
Munyai said the trading of mopane worms is a multimillion-rand industry across Southern Africa.
According to Munyai, a number of threats are facing mopane forests, but among the major ones are climate change, over/unsustainable harvesting, deforestation and overall land-use change, which are associated with various human activities.
“All these factors are leading to the loss of habitat for mopane worms and, therefore, decreasing the primary food source of mopane worms (Imbrasia belina caterpillar). At the local level, because of commercialisation and the desperate need to maximise profits, the recent harvesting methods have endangered the sustainable use of this natural resource, particularly in areas where there is no access control, for example, public and communal properties, leading to uncontrolled harvesting,” he said.
He added this has also been worsened by the disappearance of indigenous knowledge related to the sustainable use of this resource, which has protected it for centuries.
South African Environmental Observation Network researcher Tony Swemmer said there is a problem with a reduction of mopane trees over much of the Mopaneveld areas of South Africa, particularly in some parts of Giyani and Venda in Limpopo.
According to Swemmer, this is mainly a result of clearing of land for homes and crop fields around rural villages, but also due to cutting of mopane trees for use as fuel in rural homes.
He said the effects of the reduction in the number of mopane shrubs and trees on mopane worms is not known.
It is difficult to say how significant the loss of mopane worms would be for the rural people of the region in general
— Tony Swemmer, researcher
“While there is likely to be some effect, the unregulated harvesting of mopane worms in the remaining Mopaneveld is also a threat, and perhaps a bigger problem for the long-term persistence of mopane worms in these areas,” he said.
Munyai said for many years, traditional leaders and local communities have harvested wood sustainably, and non-timber and various forest products (including fuelwood) have been used mostly for subsistence.
However, he said with an increase in the commercialisation of these products, there has been over-harvesting at an alarming rate.
He said the impact of climate change on the life cycle of mopane worms is multifaceted.
Munyai said such effects include changes in temperature and rainfall patterns and, even worse, habitat loss.
According to Swemmer, the effect of climate change is a far more difficult one to answer.
“We know that mopane worm populations are extremely variable, even under natural conditions. There can be huge ‘outbreaks’ of mopane worms one year, with most trees over large areas covered in worms, followed by hardly any worms the next year. We know that rainfall plays an important role in these dynamics, and we saw a major decline in mopane worm populations during the last major drought in the region (from 2015 to 2019).”
He said as climate change intensifies, the rainfall of this region will become even more extreme, with longer intervals between rainfall events, and heatwaves will become more common.
Munyai said various ecological and monitoring studies have recently aimed to understand the dynamics between mopane trees and mopane worm populations.
According to Swemmer, there is a well-established trade in mopane worms, from rural areas of the mopane, Giyani and Vhembe districts to the urban centres of the region (such as Thohoyandou, Giyani and Phalaborwa).
He said this appears to be a significant source of income for many rural people, with worms now selling from about R70 per kilogram to as much as R170/kg.
However, Swemmer said there have not been any recent studies to estimate the current volume of trade, but based on studies from the late 1990s and more recent estimates, the trade far exceeds R100m a year.
“I don’t know of any research that has been done to estimate how important this trade is relative to the total economy of the region. There is also the direct benefit of local consumption to consider, which reduces food expenditure for many rural households. However, these benefits only last for a few weeks a year, and it is difficult to say how significant the loss of mopane worms would be for the rural people of the region in general.”
He said it is also worth noting that the supply of mopane worms from the mopane worm areas of South Africa is no longer sufficient to meet the demand, and each year worms from Botswana and Zimbabwe are brought across the border for sale in urban centres here.
Swemmer said much still needs to be learnt about the ecology of mopane worms before we can devise and implement sustainable harvesting.
He said the Northern Kruger provides an extensive protected area of mopane worms, which will ensure their survival regardless of any over-harvesting in rural areas and the impacts of global climate change.
According to Swemmer, this may prove to be a critical source of worms for re-establishing mopane worms outside the park should over-harvesting lead to local extinctions.
Would you like to comment on this article?
Sign up (it's quick and free) or sign in now.
Please read our Comment Policy before commenting.