1998, Volume 1, Paper 8
ISSN: 2209-6612

Forests as CO₂ Sinks – an Opportunity for Forest Growers?

Chris Borough
Max Bourke
David Bennett

Background

Plantation forests offer one choice in the array of options available to provide a sink for carbon dioxide (CO₂). CO₂ emissions have been increasing since the late 19th Century when industrialisation started to utilise stored non-renewable fossil fuels (coal, oil and gas) as a source of energy rather than the traditional fuels (firewood and dung) which are renewable resources.

The impact of increased CO₂ levels has been widely predicted to result in increased temperatures, a change in ocean levels through melting of polar ice caps, and changed weather patterns. Whether increased CO₂ levels will actually cause significant problems to man is not known. Scientists predict temperatures will rise by an average of 2^o Celsius and sea levels by 50 cm by the year 2100 (Fries, 1997). CO₂ levels were clearly higher in previous periods of the earth’s history; geological records indicate that large quantities of CO₂ were sequestered into coal, gas and oil during the Carboniferous Period and into limestone deposits as early as the Silurian and Ordovician Periods.

The term “Greenhouse Effect” is scientifically inaccurate. Temperatures increase in a greenhouse, but CO₂ levels are typically very low during daylight hours and commercial growers deliberately release CO₂ into the greenhouse to stimulate growth. High CO₂ levels equate to high rates of net photosynthesis and typically the growth of vegetation is limited by CO₂ levels. Raised CO₂ levels may thus not be a problem to man at least in terms of plant productivity.

The fact remains, however, that the global community does share a common concern over raised CO₂ levels and is seeking ways in which the problem may be slowed or overcome. The most obvious way to reduce CO₂ emissions is to reduce the use of fossil fuels. Alternate energy sources such as nuclear, wind, solar, hydro, wave and biomass provide one type of solution – ie change the source of fuel. The more efficient use of fossil fuels through more efficient vehicles, better mass transit systems, greater use of rail transport and use of more efficient industrial processes is another alternative.

Other methods for reducing energy consumption and, as a consequence, reducing CO₂ emissions, include using materials that use less energy in their manufacture. High-energy materials include steel, concrete and aluminium. The production of 1 tonne of steel releases around 2 tonnes of CO₂ (Forest and Wood Products Research and Development Corporation (FWPRDC), 1996). Solid timber requires a low energy input in its manufacture. Table 1 shows timber stores more than 15 times the amount of CO₂ released during its manufacture, whereas steel, concrete and aluminium store negligible amounts. 

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