Greenhouse gas emissions
Greenhouse gases (GHGs) are minor components of the atmosphere compared to nitrogen or oxygen. However, their effects are predominant in the earth's heat balance. GHGs trap thermal radiation inside the atmosphere, thereby increasing temperature and contributing to a number of secondary phenomena directly linked with high temperatures, such as increased evaporation. The main GHG is water vapour, the warming effect of which remains practically constant.
GHG emissions have grown by 70% between 1970 and 2004
GHG emissions have grown since pre-industrial times, with an increase of 70% between 1970 and 2004. The greenhouse gases, which are, directly or indirectly, affected by human activities, include carbon dioxide (CO2), methane (CH4) and nitrous oxides (N20 etc.). Agriculture contributes to all of them. In particular, land use change (essentially deforestation, burning, peat fires, decay of drained peat soils) constitutes an important source of CO2.
Agriculture and deforestation contribute more than 30% to GHG emissions.
In 2004, agricultural production and deforestation contributed 13.5% and 17.4%. respectively, to the total greenhouse gas emissions (in terms of CO2-equivalent). Contributions from agricultural production stem mainly from chemical fertilizer (N20) and livestock and paddy rice cultivation (CH4). However, emission from the food sector are even larger taking into account the whole food chain including agricultural waste, processing facilities, transport, etc. Much of the GHG emissions from agricultural production and deforestation are closely associated with rural poverty, food security and subsistence agriculture.
FAO assists countries in the establishment of monitoring systems through capacity building and develops and promotes improved methodologies to measure emissions from agriculture and deforestation.