The Courier & Advertiser (Perth and Perthshire Edition)
New greenhouse gas fear
DEEPLY BURIED organic soil rich in ancient carbon from fire ash and vegetation poses a previously unrecognised greenhouse gas threat, scientists say.
Disturbance of the soils through erosion, agriculture, deforestation, mining and other human activities risks releasing the carbon into the atmosphere, they claim.
Formed thousands of years ago, the soil layers lie many feet below the present day Earth’s surface and until now have largely been ignored.
USleadresearcherDrErikaMarin-Spiotta, from the University of Wisconsin-Madison, said: “There is a lot of carbon at depths where nobody is measuring. It was assumed that there was little carbon in deeper soils. Most studies are done in only the top 30cm.
“Ourstudyisshowingthatwearepotentially grossly underestimating carbon in soils.”
The scientists studied Brady soil, created between 13,500 and 15,000 years ago in what is now parts of the US Great Plains.
It was buried to a depth of more than 20ft by a vast accumulation of wind-born dust, known as loess, as glaciers once covering much of North America began to retreat around 10,000 years ago.
In some areas, including parts of the US Midwest and China, the dust deposits could be more than 164f t deep.
Wild fires and the rapid burial of dead vegetation led to the high carbon content.
“Most of the carbon was fire derived or blackcarbon,” saidDrMarin-Spiotta.“It looks like there was an incredible amount of fire.”
The team believe similar soils are likely to be found in many other parts of the world.
As humans increasingly disturb the land there is a danger that after being locked away for thousands of years, the carbon may be released and add to global warming.
The Brady soil consists of a three-foot thick dark ribbon providing a snapshot of an environment undergoing major and rapid change, said the scientists.
The research is reported in the latest edition of the journal Nature Geoscience.