Ag, livestock remain major sources of greenhouse gas emissions
"Adding oils or oilseeds to feed can help with digestion and reduce methane emissions. But a shift from a grass-based to a grain- and oilseeds-based diet often accompanies a shift from pastures to concentrated feedlots, which has a range of negative consequences such as water pollution and high fossil fuel consumption," said Laura Reynolds, Worldwatch Food and Agriculture Researcher and the study's author. "Aside from reducing livestock populations, there is no other clear pathway to climate-friendly meat production from livestock."
Manure that is deposited and left on pastures contributes to global nitrous oxide emissions because of its high nitrogen content. When more nitrogen is added to soil than is needed, soil bacteria convert the extra nitrogen into nitrous oxide and emit it into the atmosphere—a process called nitrification. Emissions from manure on pasture were highest in Asia, Africa, and South America, accounting for a combined 81 percent of global emissions from this source.
These data indicate the huge share of global emissions that is attributable to livestock production. While reducing livestock populations is one way to reduce global emissions from agriculture, farmers and landowners have numerous other opportunities for mitigation, many of which offer environmental and even economic co-benefits. For instance, growing trees and woody perennials on land can sequester carbon while simultaneously helping to restore soils, reduce water contamination, and provide beneficial wildlife habitat. Reducing soil tillage can rebuild soils while lowering greenhouse gas emissions. Some practices can even result in increased income for farmers—"cap-and-trade" programs allow farmers to monetize certain sequestration practices and sell them, while government programs like the U.S. Conservation Reserve Program pay farmers to set aside some of their land for long-term restoration.
Further highlights from the report:
- Enteric fermentation accounted for 29 percent of emissions in both North America and Asia in 2010—the lowest share of all regions—but was the source of 61 percent of South America's agricultural emissions, reflecting that continent's world leadership in cattle production.
- Rice cultivation was responsible for 17 percent of Asia's total emissions in 2010 but no more than 3 percent of emissions in every other region—indicating Asia's dominance of global rice output.
- Four out of the top five countries with the highest emissions from cultivated organic soils were in Asia: Indonesia contributed 278.7 million tons of carbon dioxide from this source, Papua New Guinea 40.8 million tons, Malaysia 34.5 million tons, and Bangladesh 30.6 million tons—indicating the levels of deforestation and clearing for agricultural land.