Impact of crop yield reduction on greenhouse gas emissions from compensatory cultivation of pasture and forested land

Soil organic carbon (SOC) is a major global carbon sink and is a target of carbon sequestration. SOC is also a major potential source of future emissions as conversion of land from pasture or forest to arable land leads to significant emissions of CO2 plus N2O. We have investigated the relationship between UK crop yields, land-use change and GHG emissions. There are a number of potential threats to future yields including climate change, water availability and pest pressure. Were pasture or forested land to be converted to arable land in order to compensate for lower yields then this would result in significant additional GHG emissions from SOC losses. We have modelled the impact of increasing the arable land area in the UK and other selected countries compensating for UK crop yield reductions. The predicted 20-year emissions range from under 5 x 10(6) t CO2-e to over 5 x 10(8) t CO2-e, following yield reductions of individual UK crops between 5 per cent and 30 per cent. These results suggest that crop yield reductions could have a significant adverse impact on climate change and that the maintenance or increase of crop yields is necessary in any strategy for climate change mitigation.