The research has discovered as they struggle to deal with more extreme weather, crops such as wheat and maize are generating more chemical compounds that can cause health problems for people and livestock who eat them.
“Crops are responding to drought conditions and increases in temperature just like humans do when faced with a stressful situation,” explained Jacqueline McGlade, UNEP division of early warning and assessment chief scientist and director.
The report explained that under normal conditions plants convert nitrates they absorb into nutritious amino acids and proteins. But prolonged drought slows or prevents this conversion, leading to more potentially problematic nitrate accumulating in the plant. Too much nitrate in diets can interfere with the ability of red blood cells to transport oxygen in the body. Crops susceptible to accumulating too much nitrate in times of stress include maize, wheat, barley, soybeans, millet and sorghum, the report added.
Some drought-stressed crops, when then exposed to sudden large amounts of rain that lead to rapid growth, in turn accumulate hydrogen cyanide, more commonly known as prussic acid. Prussic acid – an ingredient used in certain types of chemical warfare – interferes with oxygen flow in humans. Even short-term exposure can be debilitating for people, McGlade said.
The report quoted plants such as cassava, flax, maize and sorghum as being most vulnerable to dangerous prussic acid accumulation.
The report also noted that aflatoxins, moulds that can affect plant crops and raise the risk of liver damage, cancer and blindness are also spreading as a result of shifting weather patterns.
“We are just beginning to recognise the magnitude of toxin-related issues confronting farmers in developing countries of the tropics and sub-tropics,” the report stated. “As warmer climate zones expand towards the poles, countries in more temperate regions are facing new threats.”
The report proposes a list of eight ideas farmers can adopt to limit damage from crop toxins, such as mapping contamination hotspots and building better evidence about the toxins in their area. Developing crop varieties designed to cope with extreme weather is another way to reduce the levels of toxins in food.