100% organic farming in UK could significantly increase agriculture emissions
Release Date 22 October 2019
- Moving to 100% organic farming would reduce food yields by up to 40%, says new research
- Direct greenhouse gas emissions are reduced with organic farming
- But increased overseas land use to compensate for food shortfalls means net emissions are greater
- Storing carbon in the soil – sequestration – offsets only a small part of the higher overseas emissions
A complete shift to organic farming in England and Wales could see greenhouse gas emissions increase as more food would need to be imported, finds new research.
The research, published today (Tuesday 22 October) in Nature Communications suggests that 100% organic farming would yield up to 40% less food if the nation did not change its diet, leading to increased imports and a net increase in greenhouse gas emissions.
The team behind the research, from Cranfield University, Royal Agricultural College and the University of Reading found that while organic farming generally creates lower greenhouse gas (GHG) emissions per commodity, up to 20% lower for crops and 4% for livestock, it also produces less food energy output per hectare – and warned that if organic farming were adopted wholesale without changes to the national diet that the associated importing of food would increase agricultural emissions.
Dr Adrian Williams, Reader in Agri-Environmental Systems at Cranfield University says, “We predict a drop in total food production of 40% under a fully organic farming regime, compared to conventional farming, if we keep to the same national diet. This results from lower crop yields, because yields are restricted by a lower supply of nitrogen, which is mainly from pastureland within crop rotations or manure from cattle on grass-clover pasture.”
Assessing the need for imports to make up the shortfall, and assuming that food diets and demands stay the same, the academic team estimates that the overseas land area needed to be changed to food production for England and Wales would increase by a factor of five. This additional land would likely be of sub-optimal quality and therefore not as productive as higher-quality land.
Philip Jones, Senior Research Fellow in the School of Agriculture, Policy and Development at the University of Reading said:
“At present we use somewhere in the region of two million hectares of land to supplement our national diets. We estimate that were organic farming to be adopted wholesale without any change in diet, we would need nearly six million more hectares of land – much of which would need to come from Europe. This has an associated impact on the environment, adding potentially unnecessary food miles and greenhouse gas emissions to our food systems.”
Storing carbon in the soil
Rates of carbon sequestration – where atmospheric carbon dioxide is captured by plants and stored in the soil – are higher under organic farming because of greater use of manures and longer crop rotations. However, this is limited to the first decade or two following conversion to organic farming, as the soil will eventually reach a steady-state when carbon sequestration rates fall to zero. Overall in the 100% organic farming modelling, it was found that sequestration only offsets a small part of the higher emissions from overseas land use.
The research concluded that net GHG emissions under a 100% organic farming production method could increase by 21% over conventional farming baselines -under the assumption that only half the extra overseas land was converted from grassland - going up to 170% if the Carbon Opportunity Cost is added in.
Prof Guy Kirk, Professor of Soil Systems at Cranfield University, said:
“Although there are undoubted local environmental benefits to organic farming practices, including soil carbon storage, reduced exposure to pesticides and improved biodiversity, we need to set these against the requirement for greater production elsewhere.”
Dr Adrian Williams said:
“The assumption about diets is crucial: today’s organic consumers are a self-selecting group and not typical of the nation. Whether a different national diet could be provided by the same land area under all organic production is a different study. This was aimed at understanding limits to production. The study was based on rigorous modelling that had its foundations in establishing the biophysical limits of crop production without manufactured nitrogen.”
Smith, L.G., Kirk, G. J.D., Jones, P. J., and Williams, A. G., 2019, The greenhouse gas impacts of converting food production in England and Wales to organic methods, Nature Communications volume 10, Article number: 4641, doi: 10.1038/s41467-019-12622-7