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
Since European settlement, the native vegetation of South Australia has been extensively modified. While there is a paucity of data on the extent of pre-European forest and woodland cover, except for mainly anecdotal data for small areas such as the Adelaide Hills and Kangaroo Island, it has been estimated that 55 per cent (some 54 852 000 ha) of South Australia supported forest and woodland at the time of settlement (Wells et al 1984).
Vegetation clearance has occurred mostly in the 18 per cent of South Australia that is generally suitable for pasture and crops. Known as the agricultural area, it is approximately 155 000 km² in size and receives more than 250 mm of rain per year on average.
In 1975, 75 per cent of the agricultural area had been cleared; by 1988 this had risen to 79.9 percent. Much of the native vegetation left is in areas considered marginal for agriculture (GOSA 1988, p.106; SADEP 1989).
Recent and current situation
Until recently, clearance of native vegetation occurred at a significant rate. Native vegetation declined in the agricultural area by some 17.3 per cent (651 600 ha) between 1975 and January 1988 (GOSA 1988). A regional breakdown is given at Table 6.
|Region||Area at 1975 (ha)||Area at 1988 (ha)||Per cent change|
|Lower South-East||69 400||48 540||30.0|
|Upper South-East||256 900||98 015||61.8|
|Murray Mallee||529 000||481 256||9.0|
|Mount Lofty Ranges||39 700||36 787||7.3|
|Yorke Peninsula||67 400||59 140||12.3|
|Eyre Peninsula||1 722 400||1 375 596||20.1|
|Kangaroo Island||95 000||47 730||50.2|
|Mid-North||987 200||968 009||1.9|
|Total||3 767 000||3 115 073||17.3|
Source: Native Vegetation Authority First Annual Report and Vegetation Management Branch, Department of Environment and Planning cited in GOSA (1988, p.105)
Of this decline, 17 per cent (478 500 ha) occurred prior to the introduction of clearance controls in May 1983. An additional 162 000 ha were approved for clearance from May 1983 to the establishment of the Native Vegetation Authority in November 1985. Subsequently, only 11 000 ha have been cleared in the period to 1988. The major areas of clearance up to 1983, and the areas where the greatest pressure continues for clearance approval, are Eyre Peninsula (especially the far west and north), the South-East and Kangaroo Island (GOSA 1988, pp.105-6; also see SA Department of the Environment 1976).
Drainage of swamps and wetlands, particularly in the South-East, has contributed to the loss of large areas of native vegetation. Approximately 90 per cent of the wetlands of the South-East (4 600 km²) have been lost and many of those which remain have been significantly modified, especially through changed water regimes (Jones 1978; Ecologic and Associates 1988).
Fragmentation of remnant vegetation in the agricultural area has been substantial. For example, a survey of Fleurieu Peninsula south of Adelaide found that only nine per cent of the region was covered by original vegetation of which 67 per cent was located in blocks less than 10 ha in size. In an area of 150 000 ha only three patches exceeded 500 ha (Williams and Goodwin 1988).
Between 1985 to 1991, 31 300 ha were permitted to be cleared (SADENR data cited in NGGIC 1994, p.129a; see also GOSA 1993, pp.127,129). Table 7 below shows that from the enactment of the Native Vegetation Act in April 1991 to 30 June 1994 a total of 357.5 ha were permitted to be cleared while 5114.5 ha were permitted to be cleared with conditions. It appears that most clearing activity occurred in the year 1 July 1993 to 30 June 1994 with a total of 4675 ha permitted to be cleared (outright and with conditions) (SANVC 1992;1993;1994). It is evident that the range of measures aimed at retaining native vegetation, including native vegetation clearing controls, have effectively put an end to broadscale clearing in South Australia.
|Scattered Trees||Property Management||Wood||Brush||Other||Total|
|Total area applied for||2154.5||2757.5||3448||2901||776||12 037|
|Refused||226||1 535||2999||1231||577||6 568|
|Granted with conditions||1784.5||1040||443||1670||177||5 114.5|
Source: adapted from SANVC (1992;1993;1994)