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Forestry Facts: An Overview Statistics Old Growth Forests Biodiversity Bushfires Australia's changing forests Native forests Forests and the Economy Eucalypt (Hardwood) Plantations Pine (Softwood) Plantations Multiple use forests Woodchips Pulp and Paper Regrowth forests The World's Rainforests The Greenhouse Effect Glossary of Terms Timber construction in bushfire areas |
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The Greenhouse EffectThe earth is surrounded by gases that act like a blanket to keep it warm. We call these greenhouse gases and carbon dioxide (CO2) is among them (Booth 1989). Scientists call this warming the greenhouse effect. It is a natural feature of planet earth and helps provide the environment for living things, including people. Without greenhouse gases the earth would be too cold for life. Scientists cannot be certain of the extent to which man-made greenhouse gases have increased the earth's temperature to date. The Intergovernmental Panel on Climate Change (Bolin 1991) concluded that the global air temperature had risen by 0.3C to 0.6C in the past 100 years. But the IPCC is not sure whether this temperature rise is due to the enhanced greenhouse effect or natural climatic variations. however, the IPCC found that the level of carbon dioxide in the atmosphere could double over the next 30-50 years and that this could cause a rapid warming of the earth. Plants affect the amount of CO2 in the atmosphere Growing trees, for instance, take up CO2 out of the air and replace it with oxygen. The carbon is held in the wood fibre and will stay there until lost slowly as the wood rots, or rapidly as the wood burns. Young actively growing forests use more CO2 than older forests do. This is why forests are said to be "the lungs of the earth". So planting trees can contribute to slowing the enhanced greenhouse effect. Most of the trees planted in Australia today are planted by the forest industry. One hectare of forest will take an average of 7.5 tonnes of carbon out of the air each year during the first 30-60 years for native forests and 30 years for pine forests. (calculated from Booth 1989). Recent evidence suggests that expanding forest cover worldwide could absorb a considerable amount of carbon dioxide from the atmosphere (Pearce 1992). However, phytoplankton in the oceans is the earth's largest carbon dioxide sink. The Resource Assessment Commission (1992, p. 31) concluded that large scale expansion of plantations in Australia would absorb no more than about 10 per cent of current carbon dioxide emissions in Australia. The major source of man-made CO2 in the atmosphere is from the burning of fossil fuels such as coal.(CSIRO Division of Atmospheric Physics 1992) The energy generated from burning this coal is used to produce many products. The Resource Assessment Commission reviewed the energy efficiency of wood products and their substitutes used in the building industry. It concluded that timber was the only renewable resource and that "timber production requires far less energy than the manufacture of other materials". For example, it is estimated that timber-framed brick veneer house stores up to 7.5 tonnes of carbon. The same house with a steel frame adds about 2.9 tonnes of carbon to the atmosphere. (Turner 1989, p.6). Provided more forests are grown than are harvested, and the use of non-renewable energy sources is minimised, the manufacture of paper products also creates relatively little greenhouse gas.(Pulp and Paper Manufacturers Federation of Australia 1992, p. 7). Because of the production of wood products requires relatively little energy, using wood products means that less carbon dioxide is released to the atmosphere than when substitute materials such as steel, aluminium and plastic, which have higher energy requirements for their production, are used. References Booth T. 1989, 'Forestry and the greenhouse effect', CSIRO Forestry and Forest Products Newsletter, vol. 4, no. 1, p. 4. CSIRO Division of Atmospheric Physics 1992, Common myths and misconceptions, 'The Australian', Sydney, 5 June. Bolin B. 1991, 'Intergovernmental Panel on Climate Change (IPCC)', in Jager, J. and Ferguson, H.L., Climate Change, Science, Impacts and Policy - Proceedings of the Second World Climate Conference, Cambridge University Press. Pearce F. 1992, 'Flourishing forests mop up missing carbon', New Scientist, vol. 135, no. 1829, p. 10, Reed Business Publishing Pty Ltd NSW. The Pulp and Paper Manufacturers Federation of Australia 1992, The Challenge for Sustainable Growth, Melbourne. Resources Assessment Commission 1992, Forest and Timber Inquiry Final Report, vol. 1, AGPS, Canberra. Turner J. 1989, Forestry, the Timber Industry and the Greenhouse Effect, p. 6, Forestry Commission of NSW, Sydney. |
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