Logging to save the planet

The Forest and Wood Products Research & Development Council recently estimated that 1 billion tonnes of carbon is stored in Australian native forests designated for wood production. Presuming sustainable timber harvesting within these forests on an average 100-year rotation, new growth stimulated by logging annually sequesters 10 million tonnes of atmospheric carbon to replace carbon transferred into storage in wood products, stored in-situ in harvesting residue, or lost as waste in timber processing and regeneration burning.

The carbon sequestered by this new growth is equivalent to negating 37 million tonnes of greenhouse gas emissions - or about 7 per cent of Australia’s net annual greenhouse gas emissions. This is over and above the on-going growth of forests in conservation reserves which is also sequestering carbon at variable, but generally lower rates.

In addition to this, the supply of solid timber products reduces demand for problematic non-wood substitutes such as steel, aluminium and concrete. The manufacture of these substitutes involves the use of finite resources and substantially greater greenhouse gas emissions than required in producing the same unit of wood. For example, steel manufacture uses 350 times more energy than timber processing and aluminium manufacture about 1,400 times more.

Although it is difficult to estimate the extent to which timber products lower greenhouse gas emissions by reducing demand for non-wood substitutes, it is reasonable to presume that this, plus enhanced carbon sequestration within wood production zones, negates about 10 per cent of Australia’s annual net greenhouse gas emissions.

This is very significant given that it is roughly equivalent to the 2010 targets nominated from the $1 billion emissions abatement and renewable energy programs announced by the government in its 2004 Securing Australia’s Energy Future policy. Clearly, the cessation of wood production in Australian native forests, as is being sought by environmental NGOs, would largely counteract these government initiatives designed to help Australians embrace cleaner, “green” energy sources.

Similar to global warming, the complete cessation of native forest timber production would be counterproductive to efforts to address long term water shortages. Environmental NGOs have long portrayed logging as having a negative effect on water supplies by creating vigorous regrowth that uses substantially more water compared to unlogged mature forest.

Their assertion is supported by long term findings from catchment research conducted throughout Australia which shows, depending on forest type, that vigorously growing regrowth reduces run-off by as much as 50 per cent by age 30, but then slowly releases more run-off as it ages until by around 150 to 200 years there is a return to a pre-logging, mature forest water use regime.

To support their argument, anti-logging activists like to portray the natural state of Australian forests as being “old growth” as this maximises the gap between potential water run-off and the lesser run-off occurring in regrowth-dominated wood production zones. However, it is debatable whether Australia’s forests were ever predominantly “old growth”, and this is less likely now in view of the changed fire regimes that have accompanied European settlement. More frequent severe fires may well have irrevocably altered Australian native forests to a younger average age that allows less run-off compared to older forests that existed prior to European settlement.

Certainly, in Australia's southern states there have been massive regrowth events sparked by post-settlement fires in 1851, 1898, 1926, 1939, 1944, 1952, 1983, and 2003.

Whether such severe fires were as frequent prior to white settlement is considered unlikely because forest fuel build-up was limited by the Aborigines’ fondness for the “fire-stick” and because the many fires annually ignited by lightning were able to burn unhindered for weeks across broad swathes of country.

This contrasts sharply with the modern era where efforts are made to extinguish wildfires as soon as they are detected.

Although the aim of environmental NGOs to “lock up” forests and allow them to grow old under a passive management regime of minimal human disturbance could theoretically optimise water run-off, it is almost certainly unachievable due to the natural prevalence of wildfires which appears to be increasing in frequency and severity.