Browsing by Author "Smith, Laurence G."
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Item Open Access The greenhouse gas impacts of converting food production in England and Wales to organic methods(Nature Publishing Group, 2019-10-22) Smith, Laurence G.; Kirk, Guy J. D.; Jones, Philip J.; Williams, Adrian G.Agriculture is a major contributor to global greenhouse gas (GHG) emissions and must feature in efforts to reduce emissions. Organic farming might contribute to this through decreased use of farm inputs and increased soil carbon sequestration, but it might also exacerbate emissions through greater food production elsewhere to make up for lower organic yields. To date there has been no rigorous assessment of this potential at national scales. Here we assess the consequences for net GHG emissions of a 100% shift to organic food production in England and Wales using life-cycle assessment. We predict major shortfalls in production of most agricultural products against a conventional baseline. Direct GHG emissions are reduced with organic farming, but when increased overseas land use to compensate for shortfalls in domestic supply are factored in, net emissions are greater. Enhanced soil carbon sequestration could offset only a small part of the higher overseas emissions.Item Open Access The impacts of a large-scale conversion to organic agriculture in England and Wales(2017-07) Smith, Laurence G.; Williams, Adrian; Kirk, Guy; Pearce, BruceWith the need to identify sustainable modes of food production for growing populations there has been a growing interest in the potential of organic farming. Although evidence suggests that organic systems can produce food in an environmentally efficient manner, the impacts of a widespread conversion to organic management are still uncertain. The research presented aimed to address this knowledge gap by completing a comprehensive and robust assessment of the food production, fossil energy-use and greenhouse gas impacts associated with a 100% conversion to organic farming in England and Wales. Firstly a structured literature review was carried out to determine the relative fossil-energy efficiency of organic systems. The sustainability of typical organic crop rotations was then assessed using a simulation model of crop-soil N dynamics. Land-use and production scenarios under 100% organic management were assessed through the development and application of a large-scale linear programming model that estimates levels of production under biophysical constraints, e.g. N supplies from biological fixation by legumes. A life-cycle assessment-based model was then applied to explore the extent to which a 100% conversion to organic farming could lead to improvements in greenhouse gas mitigation and fossil energy efficiency. The environmental assessment approach allowed for processes inside and outside of the immediate boundaries of the production systems to be assessed, with the question “what is affected by the change in levels of production?” asked throughout the process. The results revealed that whilst some organic systems offer improved performance in non-renewable resource use efficiency, a widespread conversion would result in a substantial decrease in domestic food production. Total food output expressed over five major food groups fell to 64% of a non-organic baseline. An increase in food imports would therefore be required to meet demand. From a greenhouse gas perspective, a 100% conversion to organic farming in England and Wales could lead to 6% decrease in the impacts of food production. The greenhouse gas mitigation potential of organic farming is strongly related to the use of clover and other legumes in place of manufactured N and lower concentrate feed rates in livestock production. Where the additional-land required under an organic scenario is newly cultivated, it is likely that any greenhouse gas benefit obtained would be offset. Total greenhouse gas emissions increased by an average of 28%, compared to a non-organic baseline, when the land use change impacts associated with increased food imports were included. When the soil carbon sequestration benefits obtained through organic farming are also included the net difference between the two production systems is lessened, however a fundamental question remains concerning the availability of overseas land (land use requirements under organic management increased by 29-47% depending on the scenario). Reducing the area of fertility-building ley within organic rotations is likely to improve productivities and reduce land-use requirements within organic farming systems. Improving crop cultivation practices, more effective cover-cropping and improved biological N-fixation could also help to improve N efficiency and productivity within organic systems. Changes to international organic standards in some areas may also improve the environmental sustainability of the sector, e.g. by allowing recycling of P from sewage treatment. Overall the research showed that whilst the adoption of organic farming can lead to improvements in environmental performance, a widespread conversion would need to be accompanied by substantial changes in diet and/or typical organic practices to become feasible from the perspectives of environmental impact and total food production.Item Open Access Modelling the production impacts of a widespread conversion to organic agriculture in England and Wales(Elsevier, 2018-05-24) Smith, Laurence G.; Jones, Philip J.; Kirk, Guy J. D.; Pearce, Bruce D.; Williams, Adrian G.We assess the production impacts of a 100% conversion to organic agriculture in England and Wales using a large-scale linear programming model. The model includes a range of typical farm structures, scaled up across the available land area, with the objective of maximising food production. The effects of soil and rainfall, nitrogen (N) supply/offtake and livestock feed demand are accounted for. Results reveal major reductions in wheat and barley production, whilst the production of minor cereals such as oats and rye increase. Monogastric livestock and milk production also decreased considerably, whilst beef and sheep numbers increased. Vegetable production was generally comparable to that under conventional farming. Minimising the area of fertility building leys and/or improving rates of N fixation increased the food supply from organic agriculture at the national level. The total food output, in terms of metabolisable energy, was 64% of that under conventional farming. This would necessitate substantial increases in food imports, with corresponding expansion of cultivated agricultural land overseas. Significant changes in diet and reductions in food waste would be required to offset the production impacts of a 100% conversion to organic farming.