New estimates of greenhouse gas (GHG) data from the U.N. Food & Agriculture Organization (FAO) show that emissions from agriculture, forestry and fisheries have nearly doubled over the past 50 years and could increase an additional 30% by 2050, without greater efforts to reduce them.
This is the first time that FAO has released its own global estimates of GHG emissions from agriculture, forestry and other land use (AFOLU), contributing to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.
Agricultural emissions from crop and livestock production grew from 4.7 billion metric tons of carbon dioxide equivalents in 2001 to more than 5.3 billion mt in 2011, a 14% increase, FAO said, noting that the increase occurred mainly in developing countries due to an expansion of total agricultural outputs.
Meanwhile, net GHG emissions due to land use change and deforestation registered a nearly 10% decrease over the 2001-10 period, averaging some 3 billion mt of carbon dioxide equivalents per year over the decade. This was the result of reduced levels of deforestation and increases in the amount of atmospheric carbon being sequestered in many countries, FAO explained.
Averaged over the 2001-10 period, AFOLU emissions break down as follows (in carbon dioxide equivalents per year):
* 5 billion mt from crop and livestock production;
* 4 billion mt from net forest conversion to other lands (a proxy for deforestation);
* 1 billion mt from degraded peatlands, and
* 0.2 billion mt from biomass fires.
In addition to these emissions, some 2 billion mt of carbon dioxide equivalents per year were removed from the atmosphere during the same time frame as a result of carbon sequestration in forest sinks.
FAO's data based on country reports show that while those emissions continue to increase, they are not growing as fast as emissions from fossil fuel use in other sectors, so the share of AFOLU out of total anthropogenic emissions is actually decreasing over time.
The largest source of GHG emissions within agriculture is enteric fermentation — when methane is produced by livestock during digestion and released via belches — this accounted in 2011 for 39% of the sector's total GHG outputs, FAO said. Emissions from enteric fermentation increased 11% between 2001 and 2011.
Emissions generated during the application of synthetic fertilizers accounted for 14% of agricultural emissions in 2011, and are the fastest growing emissions source in agriculture, having increased some 37% since 2001.
GHGs resulting from biological processes in rice paddies that generate methane make up 10% of total agricultural emissions, while the burning of savannahs accounts for 5%.
In 2011, 45% of agriculture-related GHG outputs occurred in Asia, followed by the Americas (25%), Africa (15%), Europe (11%) and Oceania (4%), according to FAO's data. This regional distribution was fairly constant over the last decade.