Broadscale Vegetation Clearing
Australia State of the Environment Report 2001 fact sheet
Department of the Environment and Heritage, February 2002
What is happening overall?
Australian governments have introduced a range of measures in the past five years to minimise vegetation loss. While it is difficult to obtain accurate estimates of the area that has been cleared since 1996, there is a net loss of vegetative cover.
Knowing how much clearing is actually occurring is hugely problematic. There is a pressing need to establish agreed national standards for measurement of land cover changes. At the moment different agencies use different methods and the figures vary as a result. The Australian Greenhouse Office calculated that in 1999, 469,000 hectares of woody vegetation was cleared nationally. Queensland (425,000 hectares) and New South Wales (30,000 hectares) cleared the largest areas. While this shows the extent of clearing, it does not take into account areas where woody vegetation was re-established. In Queensland the clearing rates have been 47% higher in the last years of the decade compared to the years 1990-95. The Australian Greenhouse Office is developing new figures based on the use of satellite data.
What is being done to minimise vegetation loss?
- Land clearing was listed as a key threatening process under the Environment Protection and Biodiversity Conservation Act (1999) in early 2001. The listing does not give the Commonwealth power to intervene in state matters but demonstrates the importance of the issue.
- Government programs funded by the Natural Heritage Trust, such as Bushcare, focus on management of remnant vegetation, protection and revegetation through conservation plantings.
- The National Framework for Management and Monitoring of Australia's Native Vegetation was launched in March 2000 and Australian governments have developed work plans under the framework.
- The Commonwealth and the states agreed to implement 'A National Action Plan for Salinity and Water Quality in Australia' in November 2000, which among other things prohibits land clearing where it leads to unacceptable land and water degradation.
- Australia's signing of the Kyoto Protocol on greenhouse gas reductions in 1998 has stimulated research and documentation of vegetational land cover change.
Why can broadscale clearing be such a problem for the environment?
Habitats are destroyed or fragmented
The habitat of 1,000 to 2,000 birds is permanently destroyed for every 100 hectares of woodland cleared, while 200 reptiles are killed per hectare of mallee cleared. Vegetation is being fragmented into various sizes, shapes, connectivity and condition and becomes prone to invasion by weeds or feral animals.
Dryland salinity spreads
Most salinity problems in Australia result from broadscale clearing of deep-rooted native vegetation. At least 2.5 million hectares are affected by dryland salinity, and this could rise to 17 million hectares at the current rate of increase. It is estimated that 630,000 hectares of native vegetation are at risk and this could increase by up to two million hectares over the next 50 years.
Water quality deteriorates
Land clearing is also implicated in algal blooms and other problems associated with inland waters. Soil from agricultural land is washed into streams and dams, adding to the nutrient load. Nitrogen and phosphorous from catchment and streambank soil erosion generally contribute 65%-95% of nutrients entering inland waters.
The greenhouse effect is increased
Land clearing contributes to the enhanced greenhouse effect. Carbon is released into the atmosphere by clearing operations through burning of felled timber, soil disturbance, and oxidation of organic matter. In 1998, total (carbon dioxide equivalent) emissions from clearing were 81.5 megatonnes compared with 17.5 megatonnes of new carbon sinks created from regrowth associated with land clearing. Emissions from land clearing in 1999 were 89.7 megatonnes, compared with 18.0 megatonnes of sinks from regrowth.