Manure production has been a key driver of increasing concentrations of nitrous oxide ― the fourth most important greenhouse gas produced by human activity ― since 1860, according to a study published online in Nature Geoscience.

Atmospheric concentrations of nitrous oxide ― also known as laughing gas ― have risen significantly since the industrial revolution. Eric Davidson uses a model to examine the sources of nitrous oxide emissions. He shows that an increase in animal manure production explains a large proportion of the increase in nitrous oxide over the last century and a half.

He concludes that, given the increasing global demand for meat, nitrous oxide emissions from manure must be managed.