Increased ozone concentrations at ground level may be causing millions of pounds of damage to UK food crops, according to a University of York researcher.
Building on a previous study on ozone concentrations in the environment, which estimated that in 1990 alone the UK lost £130 million in crops due to ozone taken up by plants, Dr Lisa Emberson of the Stockholm Environment Institute at York has been developing new methods to calculate the amount of ozone that agricultural crops absorb.
Her figures incorporate factors such as species-specific and environmental conditions, such as growing season, drought and humidity, which, in combination with ozone concentrations, determine crop susceptibility.
Applying this new method for the UK, the loss of production in two staple crops, wheat and potato, translates into economic losses of approximately £70 million and £14 million respectively. The scale of damage varies by region according to ozone levels, climate, and crop distribution.
The figures only take into account the effect on the quantity or yield of the crop, and do not include other ozone damage such as leaf injury or poor grain quality.
"The increase in ozone levels is due to human activity," Emberson told FoodProductionDaily.com. "It is a secondary pollutant. It is formed when nitrogen oxides react with volatile organic compounds (VOCs) that are emitted into the atmosphere through fossil fuel burning and various industrial processes."
Before industrialisation, annual mean ozone concentrations were between 10 to 15 parts per billion (ppb). Concentrations have now risen to around 30 ppb, and hot sunny days in the UK lead to concentrations that can exceed 100 ppb.
Ozone is a naturally occurring atmospheric gas. High up in the earth's atmosphere, it plays a crucial role in filtering out harmful ultraviolet radiation that would otherwise damage life on earth. But at ground level, it damages human health, vegetation and materials and is also a potent greenhouse gas.
"We've tried to accurately evaluate the economic threat. Food producers are probably not aware that ozone is a regional pollutant, which makes it difficult assess," said Emberson.
"We've tried to assess the absorbed dose of ozone and calculate the exact cost this has on crop yield."
Emberson, who is co-editor of the recently published 'Air Pollution Impacts on Crops and Forests,' does believe that progress, at least in Europe, is slowly being made to reduce VOC emissions that contribute to excess levels of ozone. But she is concerned that while peak concentrations seem to have been reduced, background concentrations, especially in Asia, appear to be on the increase.
"Rather than being exposed to short sharp bursts, crops are increasingly subject to more long term exposure to high ground levels of ozone," she said. "This could potentially be very serious."
Emberson says that it is vital that food producers fully understand the combined stresses of ozone pollution and climate, especially given the projected increase in background ozone concentrations and changes in climate likely to occur in coming decades.
Work is now underway to assess the threat to maize, tomato, sunflower and sugar beet - economically important crops that are sensitive to ozone.
The Stockholm Environment Institute at York (SEI-Y) is one of the constituent centres of the Stockholm Environment Institute, an independent, international research organisation committed to the implementation of practices supportive of global sustainable development.