A/HRC/25/57 pesticides. Thanks to State support in the form of subsidies and marketing, this was effective in increasing the production volumes of major cereals (particularly maize, wheat and rice) and of soybean. The Green Revolution was an attempt to meet the challenge as it was framed at the time: to ensure that increases in agricultural productivity would match population growth and the dietary transition facilitated by rising incomes. It led, however, to an extension of monocultures and thus to a significant loss of agrobiodiversity and to accelerated soil erosion. The overuse of chemical fertilizers polluted fresh water, increasing its phosphorus content and leading to a flow of phosphorus to the oceans that is estimated to have risen to approximately 10 million tons annually. Phosphate and nitrogen water pollution is the main cause of eutrophication, the human-induced augmentation of natural fertilization processes which spurs algae growth that absorbs the dissolved oxygen required to sustain fish stocks.8 7. The most potentially devastating impacts of industrial modes of agricultural production stem from their contribution to increased greenhouse gas emissions. Together, field-level practices represent approximately 15 per cent of total human-made greenhouse gas emissions, in the form of nitrous oxide (N2O) from the use of organic and inorganic nitrogen fertilizers, methane (CH4) from flooded rice fields and livestock, and carbon dioxide (CO2) from the loss of soil organic carbon in croplands and, due to intensified grazing, on pastures. In addition, the production of fertilizers, herbicides and pesticides, the tillage, irrigation and fertilization, and the transport, packaging and conservation of food require considerable amounts of energy, resulting in an additional 15 to 17 per cent of total man-made greenhouse gas emissions attributable to food systems.9 The resulting climate changes could seriously constrain the potential productivity of current agricultural methods. For some countries, the changing climate conditions of the past thirty years already appear to have offset a significant portion of the increases in average yields that arose from technology, carbon dioxide fertilization and other factors.10 Under a business-as-usual scenario, we can anticipate an average of 2 per cent productivity decline over each of the coming decades, with yield changes in developing countries ranging from -27 per cent to +9 per cent for the key staple crops.11 8. The Special Rapporteur has shown that, partly as a result of climate change, but also due to unsustainable and destructive fishing practices and distorting subsidies, the productivity of global fisheries as a source of food is declining (see A/67/268). The unsustainable production of meat is another area of concern. An FAO study, prepared in advance of the High-level Expert Forum on How to Feed the World in 2050, estimated that annual meat production would have to reach 470 million tons to meet projected demand in 2050, an increase of about 200 million tons in comparison to the levels of 2005–2007.12 This is entirely unsustainable. Over one third of the world’s cereals are already being used 8 9 10 11 12 H.W. Paerl and V.J. Paul, “Climate change: links to global expansion of harmful cyanobacteria”, Water Research, vol. 46, No. 5 (2012), pp. 1349–1363; M.F. Chislock and others, “Eutrophication: Causes, consequences, and controls in aquatic ecosystems”, Nature Education Knowledge, vol. 4, No. 4 (2013), p. 10. High-level Panel of Experts on Food Security and Nutrition, Food Security and Climate Change, HLPE report No. 3 (June 2012). This is confirmed by more recent estimates: see S. Vermeulen, B. Campbell and J. Ingram, “Climate change and food systems”, Annual Review of Environment and Resources, vol. 37 (2012), pp. 195–222. D.B. Lobell, W. Schlenker and J. Costa-Roberts, “Climate trends and global crop production since 1980”, Science, vol. 333, No. 6042 (2011), pp. 616–620. G.C. Nelson and others, Climate Change: Impact on Agriculture and Costs of Adaptation (International Food Policy Research Institute, 2009). FAO, “How to feed the world in 2050”, at www.fao.org/fileadmin/templates/wsfs/docs/expert_paper/How_to_Feed_the_World_in_2050.pdf 5