The study, led by the London School of Hygiene & Tropical Medicine (LSHTM), is the first systematically to examine the extent to which projected changes such as increases in temperature and reduced water availability could affect the production and nutritional quality of common crops such as tomatoes, leafy vegetables and pulses. If no action is taken to reduce the negative impacts on agricultural yields, the researchers estimate that the environmental changes predicted to occur by mid- to end-century in water availability and ozone concentrations would reduce average yields of vegetables and legumes by 35% and 9% respectively. In hot settings such as Southern Europe and large parts of Africa and South Asia, increased air temperatures would reduce average vegetable yields by an estimated 31%. Environmental changes, including climate change, water scarcity and biodiversity loss, are predicted to become more profound in the 21st century -- posing significant challenges to global agriculture, food security and nutrition. While there is growing evidence that predicted future changes in temperature and rainfall will lead to significant reductions in the yields of many staple crops such as rice and wheat, the impacts on vegetables and legumes -- important constituents of healthy diets -are largely unknown. To address this evidence gap the researchers conducted a systematic review of all the available evidence from experimental studies published since 1975 on the impacts of changes in environmental exposures on the yield and nutritional quality of vegetables and legumes. Experiments included in the review were conducted in 40 countries.
The team then estimated the effects on the yields and nutritional quality of crops of changes in key environmental exposures, including increases in greenhouse gases (tropospheric carbon dioxide and ozone), reduced water availability for irrigation and rising ambient temperatures.
Previous research has shown that raised levels of carbon dioxide would increase crop yields, but this study identified for the first time that these potential yield benefits are likely to be cancelled out in the presence of simultaneous changes in other environmental exposures.
The researchers warn that in the absence of substantial efforts to respond to predicted future environmental changes, reductions in the yields of vegetables and legumes will substantially alter their availability globally. Such changes may affect the affordability and consumption of vegetables and legumes in the mid- to long-term and this could have significant impacts on population health all around the world.
Dr Pauline Scheelbeek, lead author at LSHTM, said: "Our study shows that environmental changes such as increased temperature and water scarcity may pose a real threat to global agricultural production, with likely further impacts on food security and population health.