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

Western Australia

Historical context

Almost all native vegetation clearance since European settlement has occurred in the south-west region of Western Australia in the wheatbelt, woolbelt and coastal agricultural zones. Of an estimated total cover of over 24.693 million ha, about 20.124 million ha have been cleared (George et al forthcoming). A substantial portion was cleared between 1945 and 1982 (Saunders and Curry 1990, p.303).

Significant clearance has also occurred in the Perth Metropolitan Region where some 270 000 ha of the total estimated area of 530 000 ha have been lost (Dixon et al 1994, p.58). In addition, 70 per cent of the original wetlands have been destroyed and the remaining 30 per cent have been effected to some extent by drainage, filling or mining (GOWA 1992, p.109).

Recent and current situation

It has been calculated that from 1986-87 to May 1992, about 194 800 ha of native vegetation were permitted to be cleared. These calculations are based on data available from the Soil and Land Conservation Council. On average this equates to about 32 500 ha per year (Nabben 1992). This average is consistent with the averaged estimate provided in the National Greenhouse Gas Inventory for 1988 and 1990 of 31 908 ha per year. For the period 1990-91 to December 1993 some 36 922 ha were permitted to be cleared (WA Department of Agriculture cited in NGGIC,1994, pg.129b). Table 11 shows the area of land permitted to be cleared in each district between the years 1986-87 and 1989-90.

Table 11: Total area of land permitted to be cleared by district, 1986-87 to 1989-90, (in hectares)
District 1986/87 1987/88 1988/89 1989/90
Albany 4 277 6 291 5 096 3 576
Bridgetown 1 648 - - -
Bunbury 53 129 377 564
Busselton 942 720 2 406 903
Carnarvon - - - -
Esperance 450 2 916 21 588 10 968
Geraldton 6 138 2 600 4 638 1 922
Harvey 36 305 1 149 142
Jerramungup 3 185 5 541 4 897 9 046
Katanning 1 679 1 227 472 2 692
Kununurra - - - -
Lake Grace 3 878 1 756 3 959 3 307
Manjimup 692 946 2 268 506
Merredin 2 493 3 036 3 350 2 390
Metropolitan 255 279 431 273
Moora 3 698 5 279 6 983 9 871
Narrogin 486 1 787 1 887 2 339
Northam 44 255 253 554
Three Springs 155 1 865 965 2 761
Total 30 109 34 932 60 719 51 814

Source: Adapted from Soil and Land Conservation Council data cited in Nabben (1992, Appendix 1, p. 2, table b minus table c)

Table 12: Clearing notifications, 1991-92 to end 1994
  1991-92 1992-93 1993-94 1 July to December 1994 Total (1 July 1991 to 31 December 1994)
Number of Notices of Intent to Clear 160 118 143 48 469
Area notified (ha) 12,336.92 6,066.51 13,078.00 5,022.00 36,503.43
Area without objection (ha) 10,293.22 5,254.18 9,443.47 2,856.99 27,847.86
Area retained (ha) 4,973.75 2,239.86 7,066.17 4,310.10 (1) 8,589.88
Per cent retained 40.32 36.92 54.03 86.00 -

Note:
1. In many instances, the area retained is more than the difference between area notified and area without objection (and sometimes greater than the area notified) because in negotiations with the landholder, further area under vegetation was added to the Agreement to Reserve

Source: Based on data supplied by the Commissioner for Soil and Land Conservation, Western Australian Department of Agriculture (1995)

Tables 11 and 12 show that after a peak in 1988-89 the scale of clearing appears to have begun tapering off since there has been a decrease in both the land notified to be cleared and that permitted to be cleared. Data for the six months to 31 December 1994 indicates that this trend is continuing.

Much of the remnant vegetation, however, is fragmented. There are over 300 000 small and scattered remnants on private land covering about 2.664 million ha (Beeston, pers comm 1994 cited in George et al forthcoming). Many of these remnants have large edge-to-area ratios. For example, a survey of remnant vegetation in the Midlands Division of Western Australia found that two-thirds of patches were less than 16 ha in size, only eight per cent exceeded 50 ha, and only 60 per cent of the 53 patches were considered to be relatively undisturbed (Arnold1990). Some of the effects of habitat fragmentation on the birds of this region are discussed in Chapter 2.