April 9, 2010

Grazing cows and sheep may lessen greenhouse effect

Contrary to previous studies, research scientists have recently found that grazing livestock may now reduce emissions of nitrous oxide, one of the main greenhouse gases.

Atmospheric concentrations of the greenhouse gas nitrous oxide have significantly increased with animal production as one of the main contributors. Scientists up to now have the notion that grazing would increase the release of nitrous oxide into the atmosphere. But most emissions measurements were only done during certain parts of the year and did not capture longer-term trends.

A team of researchers recently observed the nitrous oxide emissions on Inner Mongolia's steppe grassland for one whole year, measuring eight sites once a week and two sites once every three hours. Winter passed then come spring, the ungrazed sites released a large amount of nitrous oxide but heavily-grazed sites showed no such sign. The researchers conclude that the lower the density of grazers, the higher the nitrous oxide emissions during the onset of spring.

The team explains that the continual munching of sheep, goats and cows, to name a few, lowered the height of plants, decreasing the amount of snow that piled up during winter, which made the soil less insulated and thus a colder, less hospitable environment for microbes that generate nitrous oxide emissions. Other activities that reduce plant cover, like haymaking, could have a similar effect, they noted.