Land clearance continues to have a major impact on our biodiversity, soil and water. Since the mid-1990s, the rate of land clearance has been increasing. Estimates indicate that about 470,000 hectares (ha) of land were cleared in 1999, around 90% in Queensland.

The clearing of native vegetation is a key threat to Australia's terrestrial biodiversity. (SEE FOOTNOTE 1) Land clearing destroys plants, entire habitats and local ecosystems; it removes the food and habitat on which other native species rely. Clearing helps weeds and invasive animals to spread, causes greenhouse gas emissions and can lead to soil degradation, such as erosion and salinity, which in turn can harm water quality. Native bushland has cultural, aesthetic and recreational importance to many Australians.

Land is cleared for many reasons (particularly agriculture and urban development). Native vegetation is sometimes completely cleared (if crops are sown, for example). At other times only a proportion of the native vegetation is removed from an area, which may occur when land is used for mining or urban development.

Ideally, the headline indicator would consider the area of native vegetation cover in Australia. Such an indicator would require a weighted measure of the extent and intensities of land clearance and modification: apart from the practical difficulties of putting weights on different types of clearance, few accurate time series data are currently available. For the time being, estimates of land clearance from the National Greenhouse Inventory (NGI) are used. These estimates do not include all land clearance, but include the majority of intensive clearance of native vegetation.

The estimated 470,000 ha of Australian land cleared in 1999 are equivalent to over 740 football fields, each the size of the Melbourne Cricket Ground, cleared every day. Land clearance rates increased between 1991 and 1999: 40% more land (135,000 ha) was cleared in 1999 than in 1991.

UNCERTAINTY OVER THE ESTIMATES Knowing how much clearing is occurring is problematic, and these figures, from the Australian Greenhouse Office, are uncertain estimates. The most reliable figures are provided by government research agencies using satellite imagery, but data collected in this way are not available for every State over the past ten years. The accuracy of estimates is expected to improve over time. The figures used include information about land that has been cleared for the first time as well as land that has been re-cleared. They do not distinguish between the kinds of vegetation that has been cleared - for example, whether it formed part of a healthy or a degraded ecosystem. Thus the figures cannot be used to measure the net or quality-adjusted change in vegetation cover. Both clearance and re-clearance of native vegetation have environmental impacts.

SOME DIFFERENCES WITHIN AUSTRALIA

More than 90% of land clearance in 1999 occurred in Queensland where an estimated 425,000 ha were cleared. New South Wales cleared a further 30,000 ha, while clearance in the other States and Territories ranged from about 1,000 to 4,000 ha. Estimated rates of clearance before 1990 are less accurate, although the NGI figures indicate that land clearance in Queensland was continually higher than in any other State between 1970 and 1990. Over a longer period, however, other States have cleared a greater proportion of their land than Queensland, which has cleared 18% of land compared to 30% in New South Wales and the ACT and 60% in Victoria. (SEE FOOTNOTE 2)


FACTORS INFLUENCING CHANGE

Australian governments have encouraged land clearance through most of our agricultural history. Some land purchase agreements required it, taxation incentives encouraged it and agricultural departments provided advice on how to do it. But by the mid-1980s concern about the rate of loss of native vegetation had grown and governments began to establish controls on clearance.

Although the growth of cities and towns has only affected land cover over a small area (less than 0.1%) (SEE FOOTNOTE 4), it can have regional effects. Most of the urbanisation has occurred around the coast, sometimes in regions of high biodiversity, while future housing development in some areas may entail clearing endangered (now remnant) woodland communities such as the Cumberland Woodland around Sydney, now an endangered ecological community. (SEE FOOTNOTE 5)

However, agriculture has been responsible for the majority of land clearance in Australia. Although about 60% of Australia is used for agriculture, clearing has been selective, with the vegetation occupying the better soil and gentler slopes cleared first. For example, 79% of the Victorian south-east coastal plain has been cleared. (SEE FOOTNOTE 2) The most intensive agricultural land clearance has occurred in areas where crops or sown pasture have been planted.




In 2000 about 24 million ha of land were being used to grow crops and a similar area was improved pasture. These areas together represent around 10% of Australia's agricultural land and about 6% of all Australia. In the 1990s the area of land used for crops increased by over 35% from 19,000 ha in 1991, although the total area of agricultural land holdings declined slightly. This reflects the intensification, rather than spread, of agriculture over the period.

A LONGER TERM VIEW Figures from the National Land and Water Resources Audit suggest that, since 1788, over 700,000 km2 (about 20%) of woodland and forest have been cleared or thinned, primarily for crops and grazing. A further 130,000 km2 (35%) of mallee have been cleared since 1788, along with 20,000 km 2 of heath (45%), over 60,000 km2 of tussock grassland and smaller areas of other grasslands. (SEE FOOTNOTE 2) Since European settlement, land clearance has been concentrated in certain areas and ecosystems. Generally those ecosystems found on the most fertile soil have suffered the highest levels of clearance, and about 90% of vegetation in the eastern temperate zone has been removed. (SEE FOOTNOTE 3) Relatively little land clearance has occurred outside of the high rainfall and semi-arid zones, although in these areas other pressures such as grazing (both from domestic stock and introduced herbivores), weeds and changed patterns of fire are having an impact on the land. More than 90% of land clearance has occurred in 25 of Australia's 85 bioregions (areas of land that contain linked ecosystems). These bioregions occur across south-west Western Australia, southern South Australia, most of Victoria and New South Wales, and central and southern Queensland. (SEE FOOTNOTE 2)

PROTECTING AUSTRALIA's LAND While the pressures to clear land remain, Australians are responding to protect bushland. The area of land protected inside conservation reserves is growing, and in 1998-99, 60 million ha (just under 8% of Australia) were in protected areas. Some ecosystems are protected better than others: in 1998-99, 23 of Australia's 80 major biogeographic regions had less than 2% of their area protected; ten of these regions had less than 1% of their area protected and three regions had no area at all within the reserve system. (SEE FOOTNOTE 6) Legislation, such as the native vegetation acts enacted in Queensland, New South Wales and South Australia in the 1990s, targeted at controlling the clearing of native vegetation are now in force. A little less than two-thirds of Australian land is privately owned. (SEE FOOTNOTE 7) Efforts to protect biodiversity now extend beyond the reserve system into some of this private land. In 2002, for instance, there are over 5,000 community landcare groups, (SEE FOOTNOTE 8) while across Australia more than 1,300 conservation covenants - made between private landholders and governments - helped protect 774,000 ha of mostly private land. (SEE FOOTNOTE 9) Some companies and community groups also operate conservation reserves: Birds Australia for instance now has two reserves (Gluepot and Newhaven) with a combined area of over 300,000 ha.

LINKS TO OTHER DIMENSIONS OF PROGRESS

The vast majority of Australian land has been cleared for use in economic production, in particular agriculture, which has generated income and employment. But land clearance has economic impacts too. It can, for instance, lead to costs associated with reduced flood control, the provision of potable water or increased salinity and soil erosion.

Land clearance is a key pressure on biodiversity, and an estimated 1,000 to 2,000 birds permanently lose their habitat for every 100 ha of woodland cleared. (SEE FOOTNOTE 1) About 14% of Australia's total greenhouse emissions are estimated to arise from land clearance (greenhouse gases are released from the burning and decay of vegetation and from the disturbance of soil which releases carbon). Clearing vegetation plays an important role in the spread of invasive species, land degradation and declining water quality (which are important to the environment and can impose costs upon the economy).

See also the commentaries National income, Work, Biodiversity, Land degradation, Inland waters, Greenhouse gases, and Invasive species.


FOOTNOTES

1 State of the Environment Committee 2002, Australia - State of the Environment Report 2001, CSIRO Publishing, Melbourne.

2 National Land and Water Resources Audit 2001, Australian Native Vegetation Assessment 2001, National Land and Water Resources Audit, Canberra.

3 Department of the Environment, Sport and Territories 1996, National Strategy for the Conservation of Australia.s Biological Diversity, DEST, Canberra.

4 Barson, M., Randall, L. and Bordas, V. 2000, Land cover changes in Australia. Results of the Collaborative Bureau of Rural Sciences-State Agencies Project on Remote Sensing of Land Cover Change, Bureau of Rural Sciences, Canberra.

5 National Parks and Wildlife Service NSW 2001, Endangered Ecological Community Information: Cumberland Plain woodland, National Parks and Wildlife Service NSW. URL: www.npws.gov.au/wildlife/thr_profiles/Cumberland%20Plain%20Woodland.pdf last viewed 18 February 2002.

6 Environment Australia 2001, Collective Australian Protected Area Database 2000, Environment Australia, Canberra. URL: www.environment.gov.au/parks.nrs/protarea/pa99/index.html last viewed 18 February 2002.

7 AUSLIG (Australian Land Survey Information Group) 1993, Land Tenure Map URL: www.auslig.gov.au/facts/tenure/index.htm last viewed 14 February 2002

8 Landcare Australia Homepage 2002, The Dirt on Landcare URL: www.landcareaustralia.com.au/dirt last viewed 18 February 2002.

9 Binning, C. And Young, M. 1999, Talking to the Taxman about Nature Conservation, Research Report 4/99, Environment Australia, Canberra.

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