Cows absolved of causing global warming with nitrous oxide

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.