Carbon Farmers of Australia Blog

The Fire and Emergency Services Authority (FESA) in Western Australia says an increase in the number of carbon capturing tree plantations poses a huge fire risk. More native plantations have arisen in traditional farming areas since the onset of the carbon farming industry, after the Kyoto Protocol ratification came into effect in 2008 and more are expected to be planted via the CFI and the Biodiversity Fund. While there is no method for trading soil carbon offsets, trees are threatening to dominate farmland. Most of the plantations are owned by companies so have no-one onsite to put out fires when they start."By their definition these areas are carbon sequestration areas which means that in theory they're not burnt and they remain a repository to trap the carbon," says Great Southern area manager John Tonkin. "Not withstanding that, there are natural effects like lightning ... which may occur that may ... [start] these parcels of land on fire."

Could soil carbon sequestration absorb the world’s fossil fuel emissions? They have the capacity, according to soil scientist Margaret Torn from the Lawrence Berkeley National Laboratory (Berkeley Lab). co-author Schmidt, M. et al., Persistence of soil organic matter as an ecosystem property, in: Nature , 6 October, 2011. 

“The fluxes between soil carbon in the form of organic matter and carbon in the atmosphere as CO2 are very large. A small change in carbon cycling can have a huge affect on atmospheric CO2 concentrations, and therefore a huge feedback to climate change. As an example, a ten percent change in the soil carbon flux to the atmosphere would roughly double the net CO2 input. And if soils released only 0.3 percent of their carbon stores, it would equal year 2010 fossil fuel emissions.” Is the reverse true? If we were able to increase the soil’s store of carbon by 0.3% that we could absorb the world’s entire fossil fuel emissions?

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An international team of scientists have put a big question mark over important elements of the conventional paradigm of soil carbon. They cast doubt on the popular view that temperature increases automatically mean higher rates of Carbon escaping from soil. They cast doubt on the resistance of lignin and biochar to decomposition. They cast doubt on biochar’s capacity to increase soil carbon. And they recommend that scientists study soils at 3m because there is a lot going on down there. For many years, scientists thought that organic matter persists in soil because some of it forms very complex molecular structures that were too difficult for organisms to break down. An international team of 14 researchers headed by Michael Schmidt, a professor of soil science and biogeography at the University of Zurich, has now revealed that recent advances, from imaging the molecules in soils to experiments that track decomposition of specific compounds, show this view to be mistaken. For example, the major forms of organic matter in soils are in the forms of simple biomolecules, rather than large macromolecules. The team contends that the average time carbon resides in soil is a property of factors like physical isolation, recycling, or protection of molecules by minerals or physical structures like aggregates, or even unfavorable local temperature or moisture conditions, can all play a role in reducing the probability that a given molecule will decompose. 

Current models used to predict how global soil carbon will respond to climate change use simple factors like temperature dependence that indicate acceleration of decomposition in a warmer world. The decomposition-warming feedback predicts large soil carbon losses and an amplification of global warming, but in fact the authors argue this approach is too simplistic. “ The degradation speed isn't determined by the molecular structure of the dead plant debris, but by the soil environment in which the degradation takes place,” says Schmidt. For instance, the physical isolation of the molecules, whether the molecules in the soil are protected by mineral or physical structures and soil moisture influence the degradation rate of soil organic matter. Furthermore, the researchers are able to show that, contrary to the scientific consensus, there is no humic matter in the soil and this should therefore not be used for models. 

The new results cast a critical light on bioengineering experiments with plants containing high amounts of lignin or plant charcoal (biochar), with which more carbon is supposed to be stored in the soil in the long run. “Compounds such as lignin, which we thought were stable, may only last five years in soil, while proteins, which we thought were decomposable, may last more than one thousand years,” says co-author soil scientist Margaret Torn from the Lawrence Berkeley National Laboratory (Berkeley Lab). Paper: Michael W. I. Schmidt, Margaret S. Torn, Samuel Abiven, Thorsten Dittmar, Georg Guggenberger, Ivan A. Janssens, Markus Kleber, Ingrid Kögel-Knabner, Johannes Lehmann, David A. C. Manning, Paolo Nannipieri, Daniel P. Rasse, Steve Weiner & Susan E. Trumbore: Persistence of soil organic matter as an ecosystem property, in: Nature , 6 October, 2011, DOI: 10.1038/nature10386

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Photosynthesis – the process that creates soil carbon – could be taking up almost 50% more CO2 than previously estimated, according to a report in Nature, the British scientific journal. An international team of scientists have reset the bar for CO2 draw down from 120 billion tonnes per year to between 150-175 billion tonne annually… between 25% and 45% increase. This would logically mean the world’s soils have even greater capacity to store carbon. But even though they have no evidence to support the contention, the researchers declare there is no increase in soil carbon sequestration. 

The report's lead researcher Lisa Welp, from the University of California's Scripps Institute of Oceanography, said: “The extra CO2 taken up as photosynthesis is most likely returned right back to the atmosphere via respiration.” The leader of the CSIRO Changing Atmosphere research group, Paul Fraser, said “it doesn't mean they hold more carbon, they (plants) probably respire faster.” “Probably?” “Most likely?” Is this based on evidence? “I'd love to be able to say it does mean that but we just don't know that, that's in the next few steps (of research),” said Dr Fraser. 

There are two possible reactions to the higher rates of photosynthesis. One is to dismiss the possibility that it means good news for those of us who believe soils have the capacity to be a secure bridge to a low carbon future. The other is to accept these findings as further proof that there is a new paradigm that suits the times. Opposition spokesman on climate action, Greg Hunt, is among the latter when he says: “ the scientific evidence has moved more strongly in favour of the enormous potential of land and agriculture-based emissions reductions.” Which do you choose: the past or the future?

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