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V. Agricultural emissions
23. Although farming will be affected by climate change, agricultural activities are acknowledged as a significant source of greenhouse gas ( GHG) emissions and therefore a contributor to climate change. In particular: carbon dioxide (CO 2) is released by cultivation disturbance of organic carbon held in soils and vegetation and through the use of fossil fuel to power machinery and buildings; methane (CH 4) is generated by livestock digestion and from manure; and nitrous oxide (N 2O) is associated with applications of fertiliser and manure to soil. Methane has around 20 times the greenhouse effect of carbon dioxide, nitrous oxide around 300 times. For ease of interpretation, different GHGs are usually expressed in the common unit of carbon dioxide equivalents (CO 2e). Details on estimated emissions by selected sources and sinks associated with Scottish agriculture can be found at Annex F.
24. However, both scientific uncertainty and a lack of appropriate data hinder precise measurement of emissions from Scottish agriculture. Some spatial variation in some aspects of environmental conditions and management practices can be taken into account in broad types of land use. But, for example, variation in soils underlying grassland can cause emission differences unaccounted for within that land use category and the inventory methodologies are not responsive to some management practices (eg livestock diet) at all. This means that reported estimates may misrepresent the magnitude and pattern of emissions. In addition, the categorisation of emission sources for reporting purposes can mask the aggregate level of sectoral emissions.
25. The recent significant reductions in GHG emissions from agriculture can largely be attributed to reductions in livestock numbers. The economic performance of livestock agriculture in Scotland indicates that continuing downward adjustments in livestock numbers and greater overall production efficiencies within the industry are likely to take place. While this trend will result in a reduction in GHG emissions, there is nevertheless also a need to retain capacity to meet the requirements of home demand for livestock products so that possible net additional emissions arising from the production and transport of food from less environmentally efficient areas of the world are avoided. On the basis that market conditions might be expected to reflect society`s relative demand for food products as against the value it places on the impact of climate change, there is not a robust case for any unilateral policy intervention that attempts to control stock numbers.
26. Crop and livestock production remain core activities of Scottish agriculture. Improved efficiency and the use of practical, cost effective techniques to reduce operational emissions as described below must be encouraged. However there will be a limit to what can be achieved by agriculture as long as there is a continued requirement to produce food as close to the source of consumption as is possible. In terms of GHG emissions this is consistent with present strategies to reduce emissions arising from the food supply chain. Thus, in setting targets for reduced emissions from agriculture they need to be considered in relation to the overall expected food supplies that Scottish agriculture will be expected to achieve arising from its developing first National Food Policy.
27. These problems are apparent in the official reporting mechanism for Scottish emissions within the UK - the "National Inventory". This uses a relatively simplistic approach to estimating most agricultural emissions, neglecting the known heterogeneity of farming systems and the potential for management to affect emissions. In addition, agricultural emissions are reported across several different categories, only one of which is labelled explicitly as "Agriculture". The latter gives a headline figure of agriculture contributing around 13% of Scottish emissions, whereas summing across identifiable farming activities from different categories gives a figure of around 25%. On the other hand, the benefit of the National Inventory is that it provides a consistent means of measuring emissions at international level, in accordance with reporting requirements under the Kyoto Protocol.
28. Specifically, fossil fuel usage on-farm for heating and lighting plus mechanical operations is presented under the "Energy" category, but represents about 5% of total farming emissions. More significantly, carbon released from the conversion of grassland to arable crops is reported under the "Land Use, Land Use Change and Forestry" category yet represents about 45% of farming emissions. The remainder, reported explicitly under "Agriculture" refers mainly to nitrous oxide released from soils (26%) and methane from livestock digestion and manure (20%). Alternative measurement methodologies - including Life Cycle Assessment ( LCA) - categories and baselines give different figures.
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