Cassava is the staple food for more than 800 million people worldwide, including 45 per cent of those living in sub-Saharan Africa. It is extremely hardy and versatile, ideally suited for growing in drought-prone areas.
Because of this, cassava would seem like a crop made for dealing with the rising temperatures and extreme weather events associated with climate change.
Yet hardy though it is, cassava is also high in the naturally-occurring chemical compound cyanogen. When properly processed it is perfectly safe to eat, but if not, these high levels of cyanogens can lead to cyanide poisoning and a condition known as 'konzo'. 'Konzo' causes permanent paralysis of the legs and tends to affect women more than men because women are more involved in processing cassava which then leads to cyanide gases being released. When women are pregnant or breastfeeding, their bodies are also less capable of dealing with cyanide poisoning.
With AusAID funding, researchers from Monash University, the University of Eduardo Mondlane in Maputo, and the Instituto de Investigação Agrária de Moçambique have been examining toxicity levels in the cassava crops in Mozambique. This research has found that drought conditions associated with climate change can increase the levels of toxicity in cassava. It was also found that increased levels of carbon dioxide, associated with climate change, can increase the plant's toxicity.
On top of the health risks, the drought conditions that are associated with predicted changes in the climate result in reduced yields of the range of staple crops, meaning less food for the population. In countries like Mozambique where agriculture is already constrained by environmental and economic factors such as the variability of rainfall or minimal access to fertilisers and pesticides, these findings have major implications for the ability of farmers and small crop holders to provide a basic level of sustenance for themselves and their families.
The Monash researchers are now working with Government of Mozambique agricultural scientists to identify the cyanide levels of new varieties in drought conditions, and to develop cassavas that are less toxic. The team are also supporting the development of predictive mechanisms that can identify time periods of high risk as well as toxicity testing kits to reduce individual farmers' risks.
This research has contributed to a reduction in the exposure of individuals to harmful levels of cyanide toxicity and is expanding options, not only for farmers in Mozambique, but for communities across the globe who rely on this staple crop as part of their everyday diet.