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
Constraints to an analysis of recent native vegetation clearance
A number of studies have examined the issue of recent clearance of native vegetation (Bennett 1990; Scalan et al 1991; RAC 1992). At present, however, any analysis at a national level is constrained by a lack of comprehensive, precise and accurate data at State, Territory and regional levels. The situation is summarised in a report commissioned by the Resource Assessment Commission to investigate forest clearing of Australia as part of its Forest and Timber Inquiry:
Australia does not have a clear, nationwide estimate of the total extent of its forests and woodlands. At present the best estimates could be wrong by as much as three to five million hectares for Queensland alone. Nor does Australia have reliable mechanisms in each State for monitoring changes in forest estate, particularly as a result of clearing. With the possible exception of South Australia, Victoria and parts of Western Australia, land management authorities have not instituted accurate or routine procedures for mapping and documenting the area and locations of changes to forest cover. There is a particular need for this information on private and lease-hold lands (Kestel Research and Victorian Department of Conservation and Environment 1990, p.i).
This conclusion can also be applied generally to other ecosystem types, such as grasslands and wetlands.
The situation has been partially improved by the National Greenhouse Gas Inventory which includes indicative estimates of recent patterns of native vegetation clearance at national and State and Territory levels. In addition, this paper consolidates currently available information at the State and regional levels.
This analysis defines native vegetation broadly to include woody ecosystems such as forests and woodlands, as well as wetland and grassland ecosystems.
Clearance is defined as the removal of a significant proportion of one or more of the major vegetation strata in an ecosystem by mechanical or chemical means. It includes removal of woody vegetation such as forests and woodland communities, the loss of grasslands, and drainage of wetland ecosystems.
Information in this paper is primarily drawn from two sources:
- primary time series data based on the interpretation of satellite imagery (such as Landsat data used to examine the loss of native vegetation in Tasmania between 1972 and 1988) or aerial photographs (such as for various areas in the Central Division of NSW);
- secondary time series data based on native vegetation clearance permits. The area of land permitted to be cleared can be used as a general surrogate for the amount of native vegetation cleared. Generally, there is a strong correlation between the surrogate and native vegetation cleared, though the surrogate tends to overestimate the amount actually cleared.
This analysis is based mostly on secondary time series data derived from land permitted to be cleared under State planning or native vegetation management legislation. While this surrogate measure may overestimate the actual amount of vegetation cleared, any potential overestimation could be at least partially offset by illegal and other clearance which has not been recorded. Data has been sourced from the literature and State agencies.
Due to the constraints imposed by available data, the analysis tends to focus on the clearance of woody native vegetation for agricultural purposes. It does, however, include losses for other purposes, such as the loss of remnant bushland in south-east Queensland for human settlements and infrastructure, where quantitative data sets were available to the author.