Agricultural yields are not the only thing under threat from climate change. A warmer climate could also make staple food crops more toxic.
At the UN Environment Assembly, held in Nairobi in May, the United Nations Environment Programme (UNEP) issued a stark warning to the international community about the potential hazards of toxic agricultural products. In a report entitled Frontiers, UNEP placed this environmental threat on the same level as plastic pollution and emerging diseases.
The report focuses in particular on mycotoxins, a type of toxin produced by fungi that contaminate plants. There are said to be around 400 different types of mycotoxin, the most well-known of which are aflatoxins, ochratoxin A and fumonisins – strains found most commonly in maize, wheat, sorghum and groundnuts. UNEP estimates suggest that 4.5 million people will be exposed to mycotoxins in developing countries by consuming foodstuffs without quality control.
At high doses, these toxins can be immediately poisonous. At lower, more regular doses, however, they can have a carcinogenic effect. Around 40% of cases of liver cancer in Africa are said to be attributable to aflatoxins. “This is the most pressing health concern in hot, humid countries,” explains Didier Montet, food safety specialist at CIRAD, the French agricultural research and international cooperation organisation. During Montet’s field research, he claims to have observed mycotoxin doses some 1,000 times higher than the safe levels stated in the CODEX Alimentarius – a set of international standards published by WHO and FAO to protect consumer health.
One of the effects of climate change is an increase in the risk of plant contamination. “When a plant is stressed and in poor health – such as during a heatwave or drought – it can become more vulnerable to fungal infections,” explains Catherine Bessy, food safety expert at FAO. Some types of fungus also infect plants via wounds caused by insects – another phenomenon that may well become more common as the climate heats up.
“We need to develop disease and food contamination surveillance systems to cope with climate change,” adds Bessy. These systems will have to monitor foodstuffs that are already in circulation. There is also a pressing need to promote best-practice principles among farmers to take action further up the food chain. “We already have a number of simple techniques to reduce this type of contamination, such as drying seeds properly and avoiding storing them directly on the ground,” adds Montet. “Sadly, many countries lack the funding required to train farmers.”
The economic effects of crop toxicity are likely to be felt in the export and livestock farming sectors. In its report, UNEP points to the fact that drought can cause a build-up of nitrates in some plant species. If fed to livestock, these toxins can poison the animals and place the farmer’s livelihood in jeopardy.