Something Old, Something New: Scientists Trace Soils’ Contribution to Climate Change

Project leader Professor Pete Millard of Aberdeen’s Macaulay Institute explains: “Globally, soils contain over 300 times the amount of carbon released each year due to the burning of fossil fuels, and this carbon has until now, been safely locked up below ground.

“As the planet is warming up, this carbon is being released from the soil into the atmosphere as carbon dioxide, but there are in fact two types of carbon —‘new’ carbon, which has recently entered the soil through vegetation, and ‘old’ carbon, which has been locked up in the soil for years.

“It is the amount of this old carbon being lost as CO2 that has the biggest climate change effect,” he added, “as it signifies the soil changing from being a carbon-store to a source of carbon — a carbon-emitter.”

Measuring the loss of carbon from soils is relatively straightforward, but determining how much is from this old carbon has up to now proved very difficult. Now this joint project between the Macaulay Institute, Aberdeen and Landcare Research, New Zealand, has developed a method to measure the release of old carbon from soils.

Their approach is based upon the measurement of very small differences in the amount of an isotope, carbon-13, which is naturally present in all carbon dioxide, including that released by soils into the atmosphere.

“We are excited because it's very relevant at the moment. We need to predict how the climate is going to change and of course that's related to the atmosphere, the vegetation and the soil,” said Professor Millard.

Funded by the Scottish government and the Royal Society of New Zealand Marsden fund, the researchers have been working on this for three years, and now for the first time, they have been able to differentiate how much old, historical carbon is being released from soils.

“The implications of knowing this are very important and it will enable us to determine for the first time what the consequences of changes in land use might be for climate change,” said Professor Millard. “As more CO2 is released from the soil, the temperature is going to increase further — it could almost be a runway reaction.”

Also working on the project are David Whitehead, John Hunt and Margaret Barbour from Landcare Research, NZ.