Land Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Ann Hamblin, Bureau of Rural Sciences, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06748 5
Physical changes to natural habitats
Environmental indicators reported on in this section as originally listed and defined in Hamblin (1998):
| Environmental indicator | |
|---|---|
| L2.1 | Index of human accessibility related to landcover regions |
| L2.3 | Change in land use by catchments, AERs and landcover regions |
| L2.4 | Landcover change: proportion of each region covered by forest, wood, shrubs and grasses compared with 1990 baseline, by landcover and tenure |
| L2.6 | Fire control measure compared with natural fires, related to landcover regions |
Globally rapid physical change occurs naturally as the result of vulcanism, earthquakes and major storms (cyclones, tidal waves), but these effects are, apart from rainfall-related events, relatively small in a relatively stable geological continent such as Australia.
Other physical changes that happen in the short term are nearly all the result of human population change, and the technological state of the society at the time. The most widespread effects for land are related to the destruction or replacement of native vegetation and subsequent alteration of the soil environment. Fragmentation of vegetation by road and rail construction is also becoming a serious threat to the survival of fauna. (These issues are considered in detail in the Biodiversity Theme Report.)
These physical changes reduce the capacity of natural systems to grow, cycle water and nutrients, or maintain components of the original biota.
Pressure
How much of the continent is being disturbed by human activity? [L Indicator 2.1]
Environment Australia and the Australian Heritage Commission undertook a four-year study in the early 1990s to delineate those lands which appear to be 'unmodified or only slightly modified by modern or colonial society, have retained their natural character and do not contain permanent or significant habitation' (Australian Heritage Commission 1999).
An inventory of national wilderness areas was developed according to a number of specially designed criteria. The most significant for this report are the indicators of:
- remoteness from settlement, measured as the distance from centres of permanent occupation,
- accessibility, measured as distance from established access routes, including unsealed roads, and
- biophysical naturalness, measured as the degree to which the natural environment is free from disturbances caused by modern society, such as power lines, water and air emissions.
Details of the methodology and data sources can be found on the National Wilderness Inventory website.
A study carried out by CSIRO on the impact of grazing animals on biodiversity transects found that very few parts of the southern pastoral rangelands are beyond the grazing distance from watering points. In many areas the scientists could find no places suitable for their monitoring (James et al. 1996).
The Australian Heritage Commission study (AHC 1999) noted that managers have been encouraged to provide sufficient watering points to ensure that the majority of grazing lies within 3-5 km of water. They found that the average distance found by the end of the 1980s was 3.5 km for sheep rangelands, and 5.6 km for cattle. Exceptions were the most arid areas of vacant Crown land, conservation reserves and national parks. It is therefore no surprise that the full range of biodiversity or naturalness has not been preserved in the western and southern rangelands.
No data are available for south-western Western Australia (see Figures 27 and 28). The areas that are white on the maps in south-eastern and eastern Australia are regions in which the degree of accessibility is such that the areas coalesce on the maps. The Australian Heritage Commission has not yet updated the inventory, other than to add new conservation reserve locations, so the material presented here can be regarded only as a baseline for future trend studies.
Figure 27: Land disturbance calculated by remoteness from settlement, 1995.
Source: Australian Land Disturbance Database, ERIN, Environment Australia
Figure 28: Land disturbance calculated by accessibility, 1995.
Source: Australian Land Disturbance Database, ERIN, Environment Australia
Implications
Value judgments abound in the development of such an inventory, and it is not how Aboriginal or non-Aboriginal people view the areas that have been identified as wilderness. Indeed, the idea that many of the areas set aside as wilderness are 'natural' and 'pristine' may be seen by many as denying the effects of earlier Aboriginal land management practices in those areas. Aboriginal archaeological and ethnographic sites abound in such heritage areas (for example, in Kakadu, NT, and in the Franklin Gorge of Tasmania), and have been used as evidence for the need for preservation. Aboriginal peoples have had cultural traditions of stewardship that relied upon a knowledge of country and seasons (Langton 1998). In fact, in relation to ecosystem function and integrity the level of disturbance reported in these two attributes may be of value provided they are considered in the light of adaptive management, as suggested by Ludwig and Tongway (2000).