Global Warming and Pasture-Raised Beef Production in the United States ⋆ Savory Institute

Report

Global Warming and Pasture-Raised Beef Production in the United States

Union of Concerned Scientists

Gurian-Sherman, Doug. 2011. Raising the Steaks. Global Warming and Pasture-Raised Beef Production in the United States. Union of Concerned Scientists.

Key Takeaways

Agriculture emits all three major greenhouse gases— methane, nitrous oxide, and carbon dioxide—but the latter is a small part of the total in the United States and is not considered in this report.
This report evaluates the prospects for changing management practices to reduce the climate impact of the time beef cattle spend on pasture or rangeland. Improved practices are most readily applied to the finishing stage of fully pasture-raised systems—a growing alternative to CAFOs, given research showing that pasture finishing has nutritional and environmental benefits.
In the long term, the use of climate-friendly best practices in the United States may lead to substantial cuts in global warming emissions if adopted in countries where beef production accounts for a greater share of those emissions.
Well-managed pasture soils sequester carbon. Using soil to sequester carbon can reduce the climate change impact of beef production. High rates of carbon sequestration may continue for 40 years or more (Conant, Paustian, and Elliott 2001).
Sequestering organic carbon in soil provides other important benefits beyond mitigating climate change. Organic carbon aerates soil; boosts root growth, water flow, and water retention; and purifies water before it flows into groundwater.

Summary

Major findings of this report include:

the use of pasture management practices that improve the nutritional quality of forage crops could reduce methane emissions from pasture beef by about 15 to 30 percent. However, some grazing lands would not benefit from these practices, so overall reductions in U.S. global warming emissions would be considerably less than 0.5 percent—or one-third of the 1.4 percent of emissions that now come from beef production by applying these practices where appropriate.

the use of better management practices on pastures that have not been well managed, or the conversion of crop acres to pasture, could allow pastures to sequester about 0.8 to 1.0 metric ton of carbon per hectare. Better management practices on pasture could offset 0.1 to 2 percent of annual U.S. heat-trapping emissions, depending on which practices land managers adopt. Converting croplands to pasturelands could increase that amount, but new practices may involve tradeoffs in heat-trapping gases that need to be considered. In many areas, soil could continue to add carbon for several decades—until the rate at which soil loses carbon equals the rate at which it accumulates. Land managers must sustain the practices they use to enhance carbon sequestration, or soil could release the stored carbon back into the atmosphere. Best management practices used to grow crops, such as no-till methods for corn used in beef CAFOs, sequester about only half as much carbon as well-managed pasture. And only about 20 to 25 percent of U.S. corn acres now rely on no-till farming—a practice often linked to greater carbon sequestration.

best management practices available now that can reduce the climate change impact of pasture beef include:

Increasing the percentage of legumes in forage mixtures, which improves their nutritional quality and thus reduces methane emissions from cattle digestion.
Avoiding excessive use of nitrogen fertilizer to curb nitrous oxide emissions.
Using moderate stocking densities (the number of cattle per acre) to avoid excessive manure buildup and thus methane and nitrous oxide emissions, and to allow pastures to recover from grazing.
Avoiding the use of low-quality, mature pasture crops to graze cattle.
Preventing overgrazing to increase carbon sequestration in pasture soils.

other innovative practices that may have climate benefits include:

Breeding better pasture species to improve the nutritional quality of pasture forage. Higher-quality forage could reduce methane and nitrous oxide emissions by accelerating cattle growth and allowing cattle to use the nitrogen and carbohydrates in forage more efficiently.
Planting birdsfoot trefoil in pastures. This legume produces beneficial condensed tannins—compounds that may reduce methane and possibly nitrous oxide emissions.
Moving water and shelter sources to ensure that manure from grazing cattle is spread more evenly on pastures, reducing methane and nitrous oxide emissions.
Using nitrification inhibitors—chemicals that prevent the microbial processes that change ammonia to nitrous oxide—to reduce nitrous oxide emissions from urine patches.

Further research is needed to better quantify the cuts in global warming emissions from all these practices. Several other practices that optimize grazing and pasture growth— including managed rotational grazing, which entails moving grazing cattle among fenced pasture areas frequently— seem promising but also require more research. And the possible synergies of integrating several promising practices would particularly benefit from further analysis.