The report (pdf) said that U.S. crop and grazing land could sequester about 15 percent of global warming emissions from the nation’s agriculture each year.
To encourage soil’s natural tendency to capture carbon dioxide, ranchers can add irrigation, enabling pastures to sequester an additional 0.1 Mg of carbon per hectare per year. Growing improved grass species can add 3 Mg of carbon per hectare per year.
The report also recommended that ranchers prevent overgrazing, increase pasture crop productivity with a mix of crops, and add adequate amounts of nutrients from manure, legume crops or fertilizers.
“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,” UCS senior scientist and report author Doug Gurian-Sherman said.
Pasture beef cattle emit the three major heat-trapping gases – methane, nitrous oxide and CO2 – but the amount of CO2 is a small percentage of total U.S. global warming emissions, the report said.
Per ton, methane and nitrous oxide are much more damaging to the climate than CO2, the report said. 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. Crop and pasture sources of nitrogen — such as manure and fertilizer — generate 57 million metric tons of the CO2 equivalent of nitrous oxide.
The report found that improving cattle’s diet can reduce methane production of pasture-raised cattle by 15 to 30 percent. 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.
“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.”
He said that beef contributes a much greater proportion of climate change emissions worldwide than it does in the United States, so adopting these approaches internationally would have a significant impact.
Picture credit: Ella Mullins