AUSTRALIA'S method of measuring how much carbon is being stored in its soil is flawed, undermining the credibility of government programs to pay farmers to sequester the climate change inducing element, a new study by CSIRO researchers has found.
The Carbon Farming Initiative begun by the Gillard government and the Abbott-Turnbull government's Direct Action climate policy have spent millions of dollars to encourage farmers to boost carbon levels in their soils to help reduce greenhouse gas emissions and increase the productivity of the land.
However, the model used in Australia and elsewhere in the world to calculate carbon storage fails to account for soil and wind erosion, which means the carbon sink is as much as 17 per cent over-estimated over a century, according to the peer-reviewed research published last week in Nature Climate Change.
"The omission of [soil organic carbon] erosion in crop production models has implications for potential...sequestration in Australia and elsewhere," the authors, led by Adrian Chappell, a principal research scientist with CSIRO's Land & Water division, wrote.
Without accounting for the soil erosion, the accuracy of the carbon accounting is undermined and the uncertainty in estimates of how much carbon is being trapped is unnecessarily increased, Dr Chappell said.
Some farmers, for instance, may see no detectable increase in the carbon being stored even though they follow standard practices because their soil is being eroded, and the carbon is ending up elsewhere.
The 2009 "red dawn" that saw a huge region of eastern Australia cloaked in a dust storm.
The 2009 "red dawn" that saw a huge region of eastern Australia cloaked in a dust storm. Photo: Quentin Jones
"They will turn around and blame the management system," Dr Chappell said. "A whole lot of misleading outcomes will be signalled."
Likewise, farmers downwind or in valleys may inadvertently be rewarded for carbon washed or blown on to their land.
Government auction pending
The report comes just days before the Turnbull government is due to hold its second auction under the $2.55 billion Emissions Reduction Fund.
Sequestration projects such as carbon farming accounted for 28 million tonnes of the 47 million tonnes of abatement during the first auction. The payout for all winning bids totalled $660 million.
A second auction is due to be held on November 4-5, with carbon farming again likely to feature prominently among the bids.
A spokesman for Environment Minister Greg Hunt said the government was confident in the integrity of its modelling.
"Our soil carbon methodologies are world leading and have been verified and endorsed by the [Intergovernmental Panel on Climate Change]," he said. "This occurred as recently as September."
Shrinking profit margin
Dr Chappell said the Environment Department was "aware of the significance of soil erosion" for Australia's National Carbon Accounting System.
"I don't know if they are in the process of doing anything about it," he said.
Dr Chappell said measuring the loss of soil could be done by tracking changes to caesium levels as a proxy for erosion.
While fairly inexpensive, the detection of the trace element along with carbon would increase the cost for farmers and would most likely undermine the economics of the process for some.
"There's not enough of a profit margin to make it worthwhile."
The government's website uses an illustration of carbon farming as its main promotion of the ERF.
The Greens deputy leader, Larissa Waters, said the apparently flawed models used to pay for carbon abatement raised further doubts about the government's Direct Action policy.
Prime Minister Malcolm Turnbull on Thursday "said our country's success depends on respecting science", Senator Waters said.
"To live up to that rhetoric, the Prime Minister needs to take note of CSIRO's study and amend the accounting methods," she said. "More broadly, the Turnbull government needs to bring its climate policy in line with science, including by increasing [former prime minister] Tony Abbott's woeful climate targets before Paris."
Mr Turnbull will present Australia's target to cut 2005-level emissions by 26-28 per cent by 2030 at this month's climate summit in Paris.
Fairfax Media also sought comment from the ALP.
The CSIRO team is studying soil erosion not only for carbon changes but also to understand how the productive capacity of Australia's farmlands is changing.
Major dust storms, such as the "red dawn" event of 2009 that blanketed a region from Sydney to Brisbane and reached as far as the snowfields of New Zealand, are examples of how vulnerable soils are to erosion.
Not only are important nutrients and carbon being blown or leached away, the remaining soil is also more susceptible to further erosion because it can typically hold less moisture and support less vegetation, Dr Chappell said.
The prospect that future climate change will make heavy rainfall events more intense and increase the gustiness of winds will most likely exacerbate the erosion of soils in Australia and elsewhere even as populations and food demand continues to swell, he said.