SINGAPORE (Reuters) - Bushfires that have scorched Australia’s Victoria state released millions of tons of carbon dioxide and forest fires could become a growing source of carbon pollution as the planet warms, a top scientist said on Thursday.

A New Zealand firefighter is seen at the scene of a controlled bushfire near the town of Reefton, about 96km (60 miles) east of Melbourne February 17, 2009. REUTERS/Mick Tsikas

Mark Adams of the University of Sydney said global warming could trigger a vicious cycle in which forests could stop becoming sinks of CO2, further accelerating the rise of the planet-warming gas in the atmosphere.

“With increasing concerns about rising CO2, rising temperatures and reduced rainfall in many of the forested areas, then we could well see much greater emissions from forest fires,” Adams, dean of the Faculty of Agriculture, Food and Natural Resources, told Reuters.

The Victoria fires, which killed more than 200 people, were the worst in the nation’s history and many are still burning.

Firefighters battled seven wildfires in the state on Wednesday, hoping to control the flames before expected higher temperatures hit the fire-ravaged state on Friday.

“Scientists worldwide are worried about fires and forests. It doesn’t matter if it’s the Arctic tundra fires, or peat fires in Kalimantan or bushfires in Australia,” said Adams, who has worked in collaboration with the Bushfire Co-operative Research Center.

In a submission to the United Nations last year, the Australian government said wildfires in 2003 released 190 million tons of CO2-equivalent, roughly a third of the nation’s total greenhouse gas emissions for the year.

Such large, one-off releases of CO2 and other greenhouse gases such as methane, are not presently accounted for in Australia’s annual list of national greenhouse gas emissions.

If they were, the country would vastly exceed its emission limits under the Kyoto Protocol, the United Nations’ main weapon to fight climate change.

Which is why Australia is calling for amendments to rules on land use change under the United Nations so that only human activities that “can be practicably influenced” are included.

Adams said U.N. climate talks at the end of the year in Denmark that aim to agree on a successor pact to Kyoto, should discuss the growing threat from forest fires and how to develop better legal frameworks to tackle the problem.

MAJOR PROBLEM

Adams, who has studied how much carbon Australia’s forests and soil can store, has estimated that fires in 2003, which ravaged the capital Canberra, and in 2006-07 released about 550 million tons of CO2.

The current fires had already burned hundreds of thousands of hectares, he said, in areas with total carbon content of 200 tons per hectare or more.

Australia, though, was not the only concern.

Annual fires in Indonesia also release vast amounts of CO2.

Huge fires in 1997 released up to 6 billion tons of CO2, covering Southeast Asia in thick haze and causing a spike in global levels of the gas.

Research on the forest and peat fires by a team of international scientists found the blazes released the equivalent of up 40 percent of global annual emissions from burning fossil fuels.

Adams said the research was a wake-up call.

“When you see the step-increases (of CO2) that they observed, we have to sit up and take notice, that fires are a major problem,” said Adams.

He said in the past, native forest carbon had been in rough equilibrium over millions of years with fires, with very small accretion of carbon over very long periods of time.

“But then if you add rapid climate change and much greater fire frequency, the equilibrium carbon content of the native forests, instead of going up, is going to go down.”