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 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" (IPCC).
Agricultural emissions from crop and livestock production grew from 4.7 billion metric tons of carbon dioxide equivalents (CO2e) 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 CO2e 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 (in CO2e per year) break down as follows:
* 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
* 200 million mt from biomass fires.
In addition to these emissions, some 2 billion mt of CO2e 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 GHG emissions continue to increase, they are not growing as fast as emissions from fossil fuel use in other sectors, so AFOLU's share of total anthropogenic emissions is actually decreasing over time.
The largest source of GHG emissions within agriculture is enteric fermentation (Figure) — when methane is produced by livestock during digestion and released via belches — which accounted for 39% of the sector's total GHG outputs in 2011, 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%.
Geographically, 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.
The new FAO data also provide a detailed view of emissions from energy use in the agriculture sector generated from traditional fuel sources, including electricity and fossil fuels burned to power agricultural machinery, irrigation pumps and fishing vessels. These emissions exceeded 785 million mt of CO2e in 2010 and have increased 75% since 1990.
Designing responses will require detailed assessments of both GHG emissions data and mitigation options, FAO said. For instance, FAO is already generating disaggregated assessments along supply chains and analyzing the effectiveness of comprehensive mitigation interventions in the livestock sector.
"FAO's new data represent the most comprehensive source of information on agriculture's contribution to global warming made to date," said Francesco Tubiello of FAO's Climate, Energy & Tenure Division. "Up until now, information gaps have made it extremely difficult for scientists and policy-makers to make strategic decisions regarding how to respond to climate change and have hampered efforts to mitigate agriculture's emissions.
"Data on emissions for AFOLU activities support member countries in better identifying their mitigation options and enable their farmers to take faster and more targeted climate-smart responses. This, in turn, improves their overall resilience and their food security. It also allows the countries to tap into international climate funding and accomplish their rural development goals. We also see much interest in capacity development on these topics at the country level and respond to these needs through regional and country-level activities around the globe," he added.
Launched in 2012, the FAOSTAT emissions database is a key source of GHG emissions data analysis of AFOLU activities for the fifth IPPC assessment report, which is currently undergoing finalization. Data updates and enhancements will be made annually, FAO said.