Biodiversity publications archive

Native vegetation clearance, habitat loss and biodiversity decline

An overview of recent native vegetation clearance in Australia and its implications for biodiversity
Biodiversity Series, Paper No. 6

Andreas Glanznig, Biodiversity Unit
Department of the Environment, Sport and Territories, June 1995

Conclusion

This paper examined the pattern of recent native vegetation clearance. It highlighted estimates provided in the National Greenhouse Gas Inventory which indicate that in 1988 and 1990 some 700 000 ha and 650 000 ha were cleared respectively, and in the period 1983 to 1993 an average of some 500 000 ha were cleared per year for agricultural purposes. It also showed the significance of clearance for urban development, particularly in the coastal zone. The rate and scale of recent vegetation clearance in some areas of Australia is particularly pertinent.

In Queensland clearance activities have been most extensive in the northern and north-western parts of the Brigalow Belt, and in the southern and north-eastern parts of the Desert Uplands. Acacia communities around the eastern margin of the Mitchell Grass Downs also have been greatly affected. Ongoing clearing in the remainder of the Brigalow Belt, in the Mulga Lands, south-east Queensland is less extensive but is focussing on remnant vegetation and hence is no less significant for biodiversity conservation. Recently clearing has increased in the Cloncurry area, in both the Gulf Plains and the northern part of the Mitchell Grass Downs (QLDDEH 1995b).

In New South Wales clearance activities have been most extensive in a belt of land, 150 km wide, along the eastern and southern boundaries of the Western Division and the northern wheatbelt within the Central Division. Clearance has been less extensive in the rest of the Central Division, the northern tablelands and along the coastal fringe but is targeting remnant vegetation and as a result is significant for biodiversity conservation (J. Benson 1995, pers comm; Dick 1995, pers comm).

In Western Australia clearance patterns have been most extensive in the south-west. While the scale of clearing has been less than the amount cleared in Queensland and New South Wales, it has occurred in a region (the South West Botanical Province) recognised as a biodiversity 'hotspot', and hence is significant for biodiversity conservation.

The data set out in this paper demonstrates that, at a national level, it is not possible to measure with any definable accuracy the present or recent rate of native vegetation clearance. The most economically feasible way to map and measure these changes is by comparative analysis of remotely sensed data at appropriate time intervals. This method has been used to produce the most accurate State-wide data reported in this paper (eg. Victoria and Tasmania).

This situation reinforces the need for the timely implementation of actions under Objective 11.1 of the National Strategy for Ecologically Sustainable Development, particularly the action to:

assess the current rate of native vegetation clearing on a national basis, including undertaking the development of national inventories of native vegetation (COA 1992, p.56).

To meet this challenge, the Commonwealth Government recently committed $3.4 million to support a joint Commonwealth/State project to develop a better database on land clearing in Australia through collection and analysis of satellite monitoring data. Another recent initiative is the announcement by the Queensland Government of a package of measures, including the use of satellite remote sensing technology to accurately assess tree clearing rates.

While more data are required to definitively elucidate clearance trends, some coarse estimates of the expected scale of clearance have been calculated. For example, the Resource Assessment Commission Coastal Zone Inquiry estimated that over the next decade additional dwellings will require about 35 000 ha of land in non-metropolitan areas of the coastal zone (RAC 1993, p.46). In the coastal zone this scale of clearance has the potential to cause the decline and loss of many rare and endangered species and unique ecological complexes. For example, a study has shown that more than 60 per cent of Queensland's rare, threatened or endangered plants are found in the urban growth areas of south-eastern Queensland (Crome, Foran and Moore 1994).

The extent of Australia's biodiversity at risk requires a policy, planning and management approach which gives adequate consideration to the medium to long term impacts of current actions. This paper highlighted that flow-on effects resulting from, amongst other things, habitat fragmentation can take decades or even centuries to become fully evident. One mechanism which can ensure that these longer term impacts and uncertainties are adequately factored into decision making processes is the precautionary principle. This principle is one of seven guiding the implementation of the National Strategy for Ecologically Sustainable Development. The principle, and the version included in the draft National Strategy for the Conservation of Australia's Biological Diversity, appear in the box below.

National Strategy for Ecologically Sustainable Development

Where there are threats of serious or irreversible environmental damage, lack of full scientific certainty should not be used as a reason for postponing measures to prevent environmental degradation (COA 1992, p.8).

draft National Strategy for the Conservation of Australia's Biological Diversity

Lack of full knowledge should not be an excuse for postponing action to conserve biological diversity (ANZECC Task Force on Biological Diversity 1993, p.9).

The extent to which the precautionary principle is used to assist making decisions whose full environmental impacts may take decades or even centuries to become apparent will be a legacy current decision makers give to Australia's future generations.

Despite the lack of complete information, the need for strengthened action to retain native vegetation has been recognised by Governments in the National Strategy for Ecologically Sustainable Development, The National Greenhouse Response Strategy, the draft National Strategy for the Conservation of Australia's Biological Diversity and the National Landcare Program. This need was recently affirmed by the Australian and New Zealand Environment and Conservation Council which agreed that accelerated action to encourage the retention of native vegetation is a high priority in Australia.

The draft National Biodiversity Conservation Strategy provides a timetable which also acknowledges the pressing need for action, namely that 'by the year 2000 Australia will have arrested and reversed the decline of remnant native vegetation' and 'avoided or limited any further broad-scale clearance of native vegetation, consistent with ecologically sustainable management and bioregional planning, to those instances in which regional biological diversity objectives are not compromised' (ANZECC Task Force on Biological Diversity 1993, p.62).

Recent initiatives which will contribute to this end include the Commonwealth Government commitment of a further $7.5 million to the One Billion Trees Program.