Wednesday, May 18, 2011


Two of Australia's most pressing environmental problems - land degradation and the greenhouse effect - can be tackled at the same time, and Australia will be better off. That's according to Dr Roger Swift, Chief of the CSIRO's Division of Soils, who told a seminar in Adelaide today that the latest scientific research was showing clearly that reversing land degradation could soak up large amounts of the main greenhouse gas carbon dioxide - and help agriculture too.

"It's a terrific win-win opportunity for the environment," Dr Swift said. "Several new studies have found that land degradation and vegetation clearance are major sources of greenhouse gases in Australia - much larger than we previously thought.

"Carbon dioxide in the atmosphere is the main greenhouse gas. But the Earth's soils hold two or three times more carbon than our atmosphere, mostly in the form of decaying organic matter, or humus. When we over-exploit our soils, we mine that organic matter and the carbon escapes as carbon dioxide to the atmosphere.

"The good news is that the best way to improve soils is to add organic matter to them. By adding organic matter to degraded soil - and improving its structure and nutrition for future generations - we can also create a major sink for greenhouse gases. Remedying one problem will also help remedy the other."

Dr Swift said studies in the United States and Australia had found that as much as 50 per cent of the carbon which once existed in agricultural soils had been lost since the land had been turned over to farming.

Australian farm soils were much less fertile to begin with, he said, but until very recently scientists did not realise just how starved of carbon they were becoming. Because Australia had long been subject to regular bushfires, much of the land now used for farming contained a lot of small particles of charcoal.

Charcoal was made of carbon, but in soil it was largely inert, and was not available to growing plants. And there was so much old charcoal in Australian soil that it bumped up measurements of organic matter.

"If you discount the charcoal - some of which has been lying inert in the soil for decades, and perhaps centuries - then the true state of Australia's soils starts to look very much worse than we thought," Dr Swift said.

"In some of the farm soils we've measured, as much as half the carbon remaining is in the form of ancient charcoal.

"That is bad news, but it is also a great opportunity. If we improve our farming techniques so that we are restoring organic matter to the soil, not mining it out, we will be putting back some of the carbon which has escaped to the atmosphere."

Dr Swift said the worst-degraded lands in Australia tended to be those which were of marginal value for agriculture anyway; areas where the soil and climate made farming a risky business.

By progressively changing our use of such marginal land - allowing it to revegetate - and concentrating on improving soils in better areas, Australia could begin to reverse the loss of organic matter, and carbon, across a vast land area.

"The same road which leads to sustainable and prosperous farming also leads to helping alleviate the greenhouse effect," he said.

He said improved soil management could help stave off global warming, but it did not detract from the need to reduce greenhouse gas emissions. it was one more weapon to add to the anti-greenhouse armoury.

Dr Swift was giving a seminar titled "Soils and the Carbon Cycle" to a gathering of scientists from Adelaide's major soil research institutions at South Australia's Waite campus.


Embargoed until 12 noon on Thursday, September 7, 1995

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