State of the Environment

2006

Indicator: BD-08 Estimated loss of biodiversity resulting from land clearing

Data

A study by Cogger, et al on behalf of WWF, suggests that land clearing in Queensland alone kills around a 100 million animals (mammals, reptiles and birds) and a 100 million trees per year, based on 1997-1999 data. No estimate of amphibians, fish and invertebrates killed is included.

Summary of total number of selected mammals killed annually in Queensland by land clearing
Mammal Type Total Number Killed
Koalas 19 000
Possums and gliders 342 000
Echidnas > 7 500
Macropods 233 000
(kangaroos, wallabies and rat-kangaroos)  
Bandicoots 29 000
Small carnivorous marsupials 1,250,000
(dunnarts antechinuses and others)  
Rodents (native rats) 196 000
TOTAL 2 076 500

Source: Cogger, H, Ford, H, Johnson, C, Holman, J and Butler, D 2003, Impacts of Land Clearing on Australian Wildlife in Queensland, World Wildlife Foundation Australia, Sydney, Table 2, p. 19

Number of birds killed annually in Queensland by land clearing (by general vegetation type)
General vegetation type Average annual clearing rate(ha/yr) Mean bird density(birds/ha) Number of birds displaced/year
Tablelands woodland 29 800 18.9 563 220
Open Forest 9 100 31 282 100
Eucalypt Woodlands 239 200 26 6 219 200
Acacia Woodlands 133 900 10.2 1 365 780
Grassland 25 200 1.3 32 760
Rainforests 4 400 33 145 200
Wetlands 2 500 ? ?
Mangroves 800 ? ?
Heathlands/mixed shrublands 1 600 ? ?
TOTAL 446 500 120.4 8 608 260

Source: Cogger, H, Ford, H, Johnson, C, Holman, J and Butler, D 2003, Impacts of Land Clearing on Australian Wildlife in Queensland, World Wildlife Foundation Australia, Sydney, Table 5, p. 24

Number of reptiles killed annually in Queensland by land clearing
General vegetation Type/bioregion Average annual clearing rate (ha/yr) Number of reptiles killed (millions)
Brigalow Belt 260 200 52.04
Desert Uplands 51 100 10.22
Mitchell Grass Downs 26 900 5.38
Mulga Lands 85 400 17.08
South-east Queensland 7 400 1.48
All other areas 14 900 2.98
TOTAL 89 000 000 89.12

Source: Cogger, H, Ford, H, Johnson, C, Holman, J and Butler, D 2003, Impacts of Land Clearing on Australian Wildlife in Queensland, World Wildlife Foundation Australia, Sydney, Table 8, p. 29

Number of trees cleared annually from remnant areas of Queensland's broad vegetation groups (1997-99)
Broad Vegetation Group (BVG) Mean tree densities (trees/ha) Estimated no. of trees cleared (millions/yr) Percent of total trees cleared
Eucalypt woodlands on ranges. 397 11.34 6
Eucalypt open forest. 457 4.07 2
Eucalyptus tetrodonta woodlands / open forest. 466 1.02 1
Eucalyptus similis and E. whitei woodlands. 231 3.66 2
Eucalyptus populnea and E. melanophloia woodlands. 325 43.7 23
Mixed eucalypt woodlands. 421 15.97 8
Eucalyptus microneura and other box woodlands. 340 1.78 1
Eucalyptus leucophloia low open woodlands. 235 1.91 1
Riparian eucalypt woodland. 303 11.34 6
Acacia spp. woodlands and shrublands. 1022 12.77 7
Acacia harpophylla or A. cambagei open forests & woodlands. 590 60.15 31
Acacia aneura woodlands and shrublands. 523 17.06 9
Rainforests and vine thickets. 959 2.97 2
Wetlands. 798 2.67 1
Mangroves and strand communities. 916 0.6 <1
TOTAL 190 100  

Source: Cogger, H, Ford, H, Johnson, C, Holman, J and Butler, D 2003, Impacts of Land Clearing on Australian Wildlife in Queensland, World Wildlife Foundation Australia, Sydney, Table 9, p. 33

What the data mean

Gross land clearing, rather than clearing net of regrowth, needs to be considered when assessing the pressure of land clearing on biodiversity because each act of clearing eliminates all resident and dependent biodiversity. When the same area is cleared more than once, the pressure on biodiversity is cumulative because each time it is cleared a new cohort of biodiversity is destroyed. Therefore it is necessary to look cumulatively at the actual annual areas cleared, as well as the change in overall extent.

The Queensland study provides a very broad, rough average of animals killed by land clearing at about 223 native vertebrate mammals, birds and reptiles per hectare.

In the absence of any similar continent-wide study, if the Queensland averages were assumed to apply across Australia (see data limitations below), a national death toll from land clearing can be extrapolated. AGO remote sensing data suggests that around 424 727 hectares of wooded land was cleared across the continent in 2004 (See Indicator LD-03 Change in extent and proportion of woody vegetation cover, clearing and regrowth ), Using the WWF averages, the animal death toll from this land clearing, in mammals, reptiles and birds alone, would have been around 95 million animals. Across the 17 million hectares cleared since 1972, approximately 4 billion birds, reptiles and mammals would have died.

Data Limitations

Continent-wide estimates of biodiversity lost to land clearing are not available. The extrapolation of the Queensland vegetation clearing data, which includes some grasslands, to continent-wide data on woody vegetation should be seen as a very rough indicator, rather than as a serious estimate. The number of animals killed by clearing will vary considerably with the type of vegetation cleared and with where in the varied climatic and biogeographical regions of the country the vegetation occurs.

Issues for which this is an indicator and why

Biodiversity - Pressures on biodiversity - Land clearing 

The immediate effect of clearance of native vegetation on plant and animal species can be significant. When land is cleared, everything that lives in it is killed. Estimates of the number killed are a direct indicator for this pressure.

Other indicators for this issue:

Further Information

Changes to this document since December 2006

An error in transcribing data caused an error in three of the figures quoted in the interpretative text. These errors have been corrected.

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