WASHINGTON - U.S. beef cattle are responsible for 160 million metric tons of
global warming emissions every year -- equivalent to the annual
emissions from 24 million cars and light trucks. But unlike American
drivers, farmers who raise beef on pasture can reduce global warming
emissions by storing, or sequestering, carbon in pasture soils,
according to a report released today by the Union of Concerned
Scientists (UCS).

“Given the threat that climate change poses, all sectors of our
economy – including agriculture -- have to do their part,” said UCS
Senior Scientist Doug Gurian-Sherman, the author of the report. “There
is a range of affordable ways beef producers, especially those who raise
beef on pasture, can significantly reduce their impact by cutting
emissions and capturing more carbon in soil.”

The report, “Raising the Steaks: Global Warming and Pasture-Raised
Beef Production in the United States,” concluded that U.S. pasture beef
producers could reduce their annual global warming impacts by as much as
140 million metric tons, the equivalent of taking 21 million cars and
light trucks off the road.

Carbon sequestration, the report found, has the most potential for
mitigating pasture beef’s climate impact. Such practical methods as
preventing overgrazing, increasing pasture crop productivity with a mix
of crops, and adding adequate amounts of nutrients from manure, legume
crops or fertilizers, could capture significant carbon dioxide (CO2)
emissions from a variety of sources.

Pasture beef farmers also can adopt practices to cut emissions.
Pasture beef cattle emit the three major heat-trapping gases – methane,
nitrous oxide and CO2 – but the amount of CO2 is such a small percentage
of total U.S. global warming emissions that the report did not include
it. Per ton, methane and nitrous oxide are much more damaging to the
climate than CO2. Methane has 23 times the warming effect of CO2, and
nitrous oxide is nearly 300 times worse.

The 35 million head of cattle the U.S. beef industry raises annually
release more than 103 million metric tons of the CO2 equivalent of
methane into the atmosphere. Meanwhile, crop and pasture sources of
nitrogen -- such as manure and fertilizer -- generate 57 million metric
tons of the CO2 equivalent of nitrous oxide.

All beef cattle spend their first months -- and sometimes more than a
year -- on pasture or rangeland, grazing on grass, alfalfa or other
forage crops because feeding cattle grain their entire lives would cause
life-threatening illnesses. Some beef cattle live on pasture until
slaughter, but most U.S. beef cattle are fattened, or “finished,” for
several months in CAFOs (confined animal feeding operations) on corn and
other grains. 

The UCS report recommended a number of approaches that would reduce
the impact of pasture-raised beef. Most of them are more suitable for
the finishing stage of fully pasture-raised cattle systems -- which have
environmental and nutritional advantages over CAFOs -- but they also
could apply to the many months CAFO-bound cattle spend grazing on
rangeland.

One key is to improve cattle’s diet, which, in some tests, reduced
methane production of pasture-raised cattle by 15 to 30 percent. More
research is needed to accurately estimate its potential to reduce cattle
emissions nationally. Animals fed on rapidly growing or more nutritious
types of grasses and other pasture plants, which are more easily
digested, produce less methane than cattle eating older or otherwise
less nutritious pasture plants. On this more climate-friendly diet, the
animals also grow faster, need less food, and therefore produce fewer
emissions.

Gurian-Sherman examined dozens of peer-reviewed studies and found
that cattle fed a mixture of high-quality grasses and legumes such as
alfalfa produced less global warming emissions than animals fed on
grasses alone. One particularly promising legume is a plant known as
birdsfoot trefoil. Like all legumes, it adds nitrogen to the soil, which
improves the productivity of pasture grasses. But unlike most other
legumes, it contains natural chemicals known as condensed tannins, which
reduce methane production during digestion.

There are also ways to reduce nitrous oxide, which is produced by the
action of soil microbes on nitrogen in industrial fertilizers and
manure and crop residues. The report recommends that farmers use only
enough nitrogen to produce adequate pasture crop productivity because
excess use results in especially high rates of nitrous oxide. It also
recommends that farmers spread cattle more evenly around a pasture to
minimize manure buildup in particular spots. That allows more nitrogen
to be absorbed by pasture plants, leaving less for soil microbes to turn
into nitrous oxide.
 
Some studies have found that CAFO systems
produce less heat-trapping emissions than pasture systems, but those
studies relied on data that assumed low pasture nutritional quality. The
scientific literature documents that planting higher quality pasture
crops, using adequate fertilizer, and managing grazing “intensity” would
substantially reduce the disparity between CAFO and pasture systems.  

Smart pasture operations also have other advantages. Pasture-raised
cattle require far fewer antibiotics than CAFO-raised cattle, resulting
in fewer harmful antibiotic-resistant pathogens, such as Salmonella and E. coli. And pasture-raised beef contains healthier fats.

“The Department of Agriculture has a role to play here, too,”
Gurian-Sherman said. “It should sponsor more research to improve pasture
crop quality and productivity, and provide incentives to help farmers
adopt climate-friendly pasture practices.”

The report has implications beyond U.S. beef production,
Gurian-Sherman added. Worldwide, beef contributes a substantially
greater proportion of total climate change emissions than it does in the
United States, so adopting these approaches internationally would have a
significant impact. Moreover, beef production is only one facet of
animal agriculture. According to a 2006 report by the U.N. Food and
Agriculture Organization, livestock farming worldwide generates nearly
20 percent of all global warming emissions.