Cows absolved of causing global warming with nitrous oxide

Livestock could actually be good for the environment according to a new study that found grazing cows or sheep can cut emissions of a powerful greenhouse gas.

By Louise Gray, Environment CorrespondentPublished: 7:00AM BST 08 Apr 2010

The research will reignite the argument over whether to eat red meat or not Photo: REUTERS
In the past environmentalists, from Lord Stern to Sir Paul McCartney, have urged people to stop eating meat because the methane produced by cattle causes global warming.
However a new study found that cattle grazed on the grasslands of China actually reduce another greenhouse gas, nitrous oxide.

Authors of the paper, published in Nature, say the research does not mean that producing livestock to eat is good for the environment in all countries. However in certain circumstances, it can be better for global warming to let animals graze on grassland.
The research will reignite the argument over whether to eat red meat after other studies suggested that grass fed cattle in the UK and US can also be good for the environment as long as the animals are free range.
Klaus Butterbach-Bahl, of the Karlsruhe Institute of Technology in Germany, carried out the study in Inner Mongolia in China. He found that grassland produced more nitrous oxide during the spring thaw when sheep or cattle have not been grazing. This is because the greenhouse gas, also known as laughing gas, is released by microbes in the soil. When the grass is long snow settles keeping the microbes warm and providing water, however when the grass is cut short by animals the ground freezes and the microbes die.
Dr Butterbach-Bahl said the study overturned assumptions about grazing goats and cattle.
"It's been generally assumed that if you increase livestock numbers you get a rise in emissions of nitrous oxide. This is not the case," he said.
Estimated nitrous oxide emissions from temperate grasslands in places like Inner Mongolia as well as vast swatches of the United States, Canada, Russia and China account for up a third of the total amount of the greenhouse gas produced every year. Nitrous oxide is the third most important greenhouse gas after carbon dioxide and methane.
But Dr Butterbach-Bahl pointed out that the study did not take into account the methane produced by the livestock or the carbon dioxide produced if soil erodes. He also pointed out that much of the red meat eaten in the western world if from intensively farmed animals in southern countries.
He said the study does not overturn the case for cutting down on red meat but shows grazing livestock is not always bad for global warming.