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How is ozone pollution reducing our food supply?
5th Dec 2011
Plant biologists from the Lancaster Environment Centre (LEC), Lancaster University, and from the Centre for Ecology and Hydrology, Bangor, have highlighted the ways that ozone pollution can reduce our food supply in their recent article published in the Journal of Experimental Botany. They describe how ozone is damaging our staple food crops when they are growing in farmers' fields. They also report that this problem may well become worse in the future, especially in, for example, SE Asia.
Ozone is a polluting gas in the air around us formed from emissions from motor vehicles and from industry. At ground level, ozone is damaging, even though we need it in the upper atmosphere to protect us from UV radiation. Its concentration here at ground level has been increasing since the middle of the last century, so that it is now present at levels high enough to injure plants. It can stop them from fixing sunlight into energy via photosynthesis, can cause their leaves to die and fall off early, and can stunt their growth. All this means that the damaged plants have fewer resources (carbon and nutrients) to put towards forming their edible parts, such as wheat and rice grains, maize kernels, potato tubers, pea and bean pods and so on. Sometimes the effects are not even visible to the naked eye because they accrue over the course of the whole growing season so a farmer may not even realise why his or her yield is smaller. Also, it is difficult to tell without sophisticated monitoring equipment when the air around us has become polluted enough with ozone to affect plants.
Because ozone pollution is predicted to become worse in some areas such as Asia in the next two or three decades, where much of our global food supply is sourced, it may soon have an even bigger impact on crops in farmers fields. Furthermore, ozone's capacity to reduce yields may be compounded by other types of climate change. For example ozone reduces the ability of some plant varieties to withstand other stresses such as drought, and we predict, says one of the LEC scientists Dr. Sally Wilkinson, that the same may be true of some crop varieties. However other varieties are actually protected from some of the effects of ozone pollution by drought, because pores in the leaf surface through which ozone can enter the plant are often closed in droughted conditions. More research is needed to choose carefully which crop varieties can withstand ozone pollution, especially when it is combined with other types of environmental stress. This is particularly important for food security, given the increasing world population, which needs more, rather than less food to be grown by our farmers, despite the increasingly erratic climate that we and our food plants are being subjected to.
Further information on the economic impacts of ozone damage to crops in Europe, on which crops are the most sensitive to ozone, along with a review of the implications for food supplies from SE Asia, can be found in two new reports written by Dr Gina Mills and colleagues at CEH Bangor with inputs from the Lancaster University scientists (downloadable from http://icpvegetation.ceh.ac.uk/).
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