Save the Planet, Cut Down a Tree

The latest round of restrictions on broad-scale tree clearing in NSW and Queensland were driven in part by the Federal Government's global warming concerns and our Kyoto greenhouse gas emissions target.

But research recently published in a science journal Nature, suggests trees may in fact be a source of greenhouse gases.

In Japan, in 1997, the Federal government agreed to a target of limiting greenhouse gas emissions to 108 per cent of 1990 emissions by 2012 as part of the Kyoto Protocol.

The Government never formalised this agreement, but Environment Minister, Ian Campbell, has boasted we will nevertheless meet the target in part by stopping tree clearing.

In fact, it had been calculated that the vegetation management legislation introduced into Queensland and NSW over the last few years would contribute to a net reduction in carbon dioxide emissions of about 25 million tones.

By comparison the transport sector (where over half of emissions are from cars) is projected to grow by about 33 million tones by 2012.

Central to the Kyoto accounting systems is the idea that forests are a net sink for greenhouse gases because trees store carbon dioxide, while factories and cars, for example, are a source of greenhouse gases because they generate carbon dioxide.

But the new research shows that while trees store carbon dioxide, they emit methane and methane is about 20 times more potent as a greenhouse gas than carbon dioxide.

So forests may in fact be a source of greenhouse gases.

This is an extraordinary finding likely to result in a rewrite of the Kyoto rule book and further complicate greenhouse gas accounting.

CSIRO has played down the finding, suggesting that methane from a radiate pine plantation would off-set only about 5 percent of the amount of carbon dioxide stored by trees in terms of global warming.

But tropical forests are thought to contribute much more methane than, for example, pine plantations in southern Australia.

Interestingly, while it was once suggested that Australia could meet its total emission reduction targets by eliminating cattle because these ruminants release methane as flatulence, this new research suggests a forest may produce more methane than an equivalent area of grazed pasture.

Given climate change is the top environmental issue, the more zealous among the farming community may use the finding as an opportunity to promote the slogan, "save the environment, cut down a tree"!

While it is a bit more complex than this, now is certainly a good time for the agriculture lobby to demand the Government rethink its vegetation management legislation.

It might also be a good time to ask our scientists and science managers:  "How could such a potentially large source of greenhouse gases have been overlooked?"

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