These findings, published online in Nature Climate Change, demonstrate that the wider implications of biofuel cultivation need to be assessed alongside their potential to save carbon.

Biofuels — usually derived from specialist crops such as poplar, willow or eucalyptus — constitute one of the alternative energy sources being advocated as part of the solution to society’s reliance on carbon-intensive fossil fuels. However, many plant species grown for biofuel emit more isoprene, an ozone precursor, than the traditional crops they replace.

A modelling case study by Professor Nick Hewitt, Dr Oliver Wild and former LEC PhD student Kirsti Ashworth estimates the increase in ground level ozone pollution likely to result from a change to biofuel crops, and the associated impacts on human health and agricultural production.

In the case study, enough land area in Europe to meet the European Union’s 2020 goal for biofuel production was converted to short rotation coppice crops and the effects on human mortality and crop productivity estimated.

Professor Hewitt said: "Growing biofuels is thought to be a good thing because it reduces the net amount of carbon dioxide emitted to the atmosphere, but biofuels could also have a detrimental effect on air quality. Large-scale production of biofuels in Europe would have small but significant effects on human mortality and crop yields.”

The paper entitled "Impacts of biofuel cultivation on mortality and crop yields" uses a model of atmospheric chemistry to estimate the changes in ground level ozone concentrations that will result from the large scale planting of short rotation coppice biofuel crops in Europe.

These changes in ozone concentration occur because short rotation coppice tree species emit much more of a reactive volatile organic compound, isoprene, than do grass and other food crops. Isoprene then takes part in chemical reactions in the lower atmosphere that lead to the formation of ozone.