8.3 Emission trends (global and regional)

With an estimated global emission of non-CO₂ GHGs from agriculture of between 5120 MtCO₂-eq/yr (Denman et al., 2007) and
Errata 6116 MtCO₂-eq/yr (US-EPA, 2006a) in 2005, agriculture accounts for 10-12 % of total global anthropogenic emissions of GHGs.
Errata Agriculture contributes about 47% and 58% of total anthropogenic emissions of CH₄ and N₂O, respectively, with a wide range of uncertainty in the estimates of both the agricultural contribution and the anthropogenic total. N₂O emissions from soils and CH₄ from enteric fermentation constitute the largest sources, 38% and 32% of total non-CO₂ emissions from agriculture in 2005, respectively (US-EPA, 2006a). Biomass burning (12%), rice production (11%), and manure management (7%) account for the rest. CO₂ emissions from agricultural soils are not normally estimated separately, but are included in the land use, land use change and forestry sector (e.g., in national GHG inventories). So there are few comparable estimates of emissions of this gas in agriculture. Agricultural lands generate very large CO₂ fluxes both to and from the atmosphere (IPCC, 2001a), but the net flux is small. US-EPA, 2006b) estimated a net CO₂ emission of 40 MtCO₂-eq from agricultural soils in 2000, less than 1% of global anthropogenic CO₂ emissions.

Both the magnitude of the emissions and the relative importance of the different sources vary widely among world regions (Figure 8.2). In 2005, the group of five regions mostly consisting of non-Annex I countries was responsible for 74% of total agricultural emissions.

In seven of the ten regions, N₂O from soils was the main source of GHGs in the agricultural sector in 2005, mainly associated with N fertilizers and manure applied to soils. In the other three regions - Latin America and The Caribbean, the countries of Eastern Europe, the Caucasus and Central Asia, and OECD Pacific - CH₄ from enteric fermentation was the dominant source (US-EPA, 2006a). This is due to the large livestock population in these three regions which, in 2004, had a combined stock of cattle and sheep equivalent to 36% and 24% of world totals, respectively (FAO, 2003).

Emissions from rice production and burning of biomass were heavily concentrated in the group of developing countries, with 97% and 92% of world totals, respectively. While CH₄ emissions from rice occurred mostly in South and East Asia, where it is a dominant food source (82% of total emissions), those from biomass burning originated in Sub-Saharan Africa and Latin America and the Caribbean (74% of total). Manure management was the only source for which emissions where higher in the group of developed regions (52%) than in developing regions (48%; US-EPA, 2006a).

The balance between the large fluxes of CO₂ emissions and removals in agricultural land is uncertain. A study by US-EPA (2006b) showed that some countries and regions have net emissions, while others have net removals of CO_2. Except for the countries of Eastern Europe, the Caucasus and Central Asia, which had an annual emission of 26 MtCO₂/yr in 2000, all other countries showed very low emissions or removals.