by Ben Davis
Droughts are not uncommon across the African continent, particularly during the dry season. The dry seasons of Southern African countries (such as Namibia, Zambia and South Africa) roughly coincide with the winter months in the Southern Hemisphere, namely April to October. The dry season of East African countries (such as Kenya and Uganda) runs from June to September. Droughts are however becoming increasingly unpredictable and prolonged, spanning multiple dry seasons and omitting the intervening wet seasons altogether. An example of such prolonged drought is the current drought affecting Southern Africa since 2018.
You may naturally assume that droughts have a rather simple impact on crops. Lack of water means that farmers cannot irrigate crops such that they wilt and eventually die. You’d be right - this is typically what happens, resulting in dwindling food supplies in the affected countries. However, plants are clever. In recognising that such extreme, climate change-induced droughts aren't going away anytime soon they’ve found a way of chemically developing drought resistance. This process is called cyanogenesis and it presents great dangers for food security.
During cyanogenesis, leaves undergo a tissue decomposition in which cyanide, present in the tissues, is freed from its chemical bond. The cyanide then forms hydrocyanic acids. These acids, one namely being gaseous hydrogen cyanide, are toxic to animals including humans. Toxic plants are then either directly consumed by people or ingested by livestock where they accumulate. Such toxins are causing outbreaks of aflatoxin poisoning amongst pastoralist/farmer populations in many LIDCs (Low Income Developing Countries), where the food they cultivate is their only source of sustenance. Amidst the drought, the only crops they are able to eat are those that have survived the drought (most probably those with toxins). They do not have the option to discard the food once acknowledging it’s poisonous and so must consume the cyanide toxins- hence developing aflatoxin poisoning.
Why is Cyanogenesis so problematic ?
The International Livestock Research Institute (ILRI) have estimated that 26,000 people in sub-Saharan Africa alone die annually of liver cancer associated with aflatoxin exposure. Sadly, the problems don't stop there. With crops being a primary export from many LIDCs (such as those in Africa), the toxins are expected to become more widespread across the globe, with many developed countries expected to see more aflatoxin-associated deaths in the future.
What are the solutions ?
Climate change is the principal factor pushing crops to develop drought resistance.
Plants are having to withstand drought more than ever before and so, trying to find a way to ensure the consistency of rainfall patterns is key. Achieving this however is a prolonged process and requires us to resolve global climate issues before regional climates begin to shift. We must therefore look to temporary solutions that can be quickly implemented.
For example, ensuring that there is adequate crop variety is a key way to ensure that populations are not reliant on one species of crop (that may have developed the toxins). In prioritising crop variety, populations can diagnose and dispose of toxic crop yields whilst selling and eating others.
Reading
Jacqueline McGlade, ‘Food Security: A poisoned chalice of plant adaptation’(2019) here
Kris Taylor, ‘Saving the magic in our soils’ here
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