Large Mammals Had an Impact on the Global Climate
27.05.2010 - Atmosphere & Space, Flora & Fauna, Bi-polar
More than 13,000 years ago, millions of large mammals such as mammoths, mastodon, shrub-ox, bison, ground sloths and camels roamed the Americas and may have had profound influences on the environment according to research released in the publication Nature Geosciences Sunday.
The extinction of these large herbivores probably led to an abrupt decrease in methane emissions and atmospheric concentrations of the gas with potential implications for climate change.
Herbivores produce methane as a by-product of cellulolytic-microbial fermentation during the digestive process. Past studies have shown that domestic livestock are an important contributor to greenhouse gas concentrations and can represent ~20 percent of annual emissions. The study says that this influence may have been greater in the Pleistocene epoch when methane concentrations were considerably lower.
The researchers looked at 114 different herbivorous species that were extirpated from the Americas at the end of the Pleistocene epoch. Using ice cores to determine the amount of methane during the onset of the Younger Dryas cooling period, they found the extinction of megafauna closely coincides with an abrupt drop in atmospheric methane concentration.
With that information, the researchers then decided to try and determine how much methane was produced by these species. They came up with an estimate of the number of animals and then an estimate of how much methane those animals actually produced.
Ice core records from Greenland suggest the methane concentration change associated with a 1 degree Celsius temperature shift ranges from 10 to 30 parts per billion by volume with a long term mean of about 20 ppbv. A drop of 185 to 245 ppbv methane drop observed at the Younger Dryas stadial is associated with a temperature shift of 9 to 12 degrees Celsius. The calculations suggest that decreased methane emissions caused by the extinction of New World megafauna could have played a role in the Younger Dryas cooling event.
