Livestock's Long Shadow: Environmental Issues and Options is a United Nations report, released by the Food and Agriculture Organization (FAO) of the United Nations on 29 November 2006, that "aims to assess the full impact of the livestock sector on environmental problems, along with potential technical and policy approaches to mitigation".
Livestock's Long Shadow is an assessment of recent research, taking into account direct impacts of livestock production, along with the impacts of feed crop cultivation. The report states that the livestock sector is one of the top two or three most significant contributors to serious environmental problems. The findings of this report suggest that it should be a major policy focus when dealing with problems of land degradation, climate change and air pollution, water shortage and water pollution, and loss of biodiversity.
Senior author Henning Steinfeld stated that livestock are "one of the most significant contributors to today’s most serious environmental problems" and that "urgent action is required to remedy the situation."
Land use and land use change: 2.5 Gigatonnes carbon dioxide equivalent; including forest and other natural vegetation replaced by pasture and feed crop in the Neotropics (CO2) and carbon release from soils such as pasture and arable land dedicated to feed production (CO2)
Feed Production (except carbon released from soil): 0.4 Gigatonnes CO2 equivalent, including fossil fuel used in manufacturing chemical fertilizer for feed crops (CO2) and chemical fertilizer application on feed crops and leguminous feed crop (N2O, NH3)
Animal production: 1.9 Gigatonnes CO2 equivalent, including enteric fermentation from ruminants (CH4) and on-farm fossil fuel use (CO2)
Manure Management: 2.2 Gigatonnes CO2 equivalent, mainly through manure storage, application and deposition (CH4, N2O, NH3)
Processing and international transport: 0.03 Gigatonnes CO2 equivalent
In a 2009 article in the Worldwatch Institute magazine it was claimed that the FAO report was too conservative and that livestock sector accounts for much more of global GHG emissions, at least 51%. A 2011 response to this was published by FAO and an international coalition of scientists, discrediting the magazine article and upholding the 2006 assessment. In 2013 many of the same authors of the first report published a subsequent study for the FAO, revising their estimate of anthropogenic greenhouse gas emissions due to livestock downward to 14.5%.