Land and its Changing Use

Introduction

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The land's vegetation cover is never static, especially over the longer term. The Australian continent has been subject to various climatic changes, not least those associated with the most recent ice ages, all of which resulted in significant changes to the vegetation. To such evolutionary changes must be added those resulting from the thousands of years of Aboriginal occupation. Their burning practices, to provide fresh plant growth and assist in the hunting of native fauna, resulted in the maintenance of associated open woodland and grasslands and the increased presence of fire-tolerant species. Thus, at the time of arrival of the first European settlers, the native vegetation over much of Australia, including the Murray-Darling Basin, could not be described as 'natural' as it had already experienced considerable change (Figure 1).

Figure 1 Land use in the MDB (source based on MDBMC 1987)

The impact of the Aboriginal peoples on the vegetation was real but gradual, in marked contrast to that of the European settlers. Their impacts, in no more than two hundred years and a very much shorter period over most of the Basin, have been both intensive and extensive (Carnahan et al. 1990, 54). This was the period that Eric Rolls has called "our white adolescence". Land clearing on a massive scale has taken place (Walker et al. 1993), replacing the diverse native vegetation with agricultural landscapes, plantation and regrowth forests, urban areas and communication corridors. In fact, for Australia as a whole, recent studies have indicated that over 20 per cent of the native vegetation has been cleared for agricultural and other purposes, compared with previous estimates of 6 to 8 per cent. The figure rises to 52 per cent in what has been termed the ‘intensive land use zone’ of the continent, which includes much of the MDB (Graetz et al. 1995). At least half of the Basin's pre-European vegetation cover has been removed. Many new plants and animals have replaced the native ones. Especially in the arid and semi-arid areas, many native species are not regenerating. Many species have been lost, not least those of the native grasslands. There is little wilderness of high quality remaining in the Murray-Darling Basin (AHC 1995). Australia has an unfortunate record of such flora and fauna losses, and many animals and plants remain on the endangered list.

However, whilst much of the remaining natural vegetation is still at risk of being cleared, with very little left in some areas, an increasing proportion is now contained in managed reserves of one kind or another, though many of these remain vulnerable to future disturbance (Graetz et al 1995) (see National Parks and other Reserves). Of considerable importance are the remnant vegetation sites, small areas of native plant communities outside the boundaries of parks and reserves, that have remained relatively untouched. Many are small and unconnected, and insufficient to conserve the dependent fauna. For example, it is estimated that no more than 0.5 per cent of native grasslands are left in south-east Australia, with much of these being along roads, railway lines, stock routes, and in old cemeteries. Such remnants are under increasing pressure, in all kinds of locations, both rural and urban. They need to be conserved as much as the parks. In fact, what areas remain of the native grasslands are perhaps in greater need of protection than some forest areas.

Over the period of European settlement, the Murray-Darling Basin has been the location of some of the most extensive and dramatic vegetation cover changes in Australia. The major ones have been the clearing of eucalypt woodland and shrubland in the drier areas and their replacement by crops and pastures, notably in what has long been known as the wheat-sheep belt that stretches from south-east Queensland through New South Wales and northern Victoria into South Australia. Over large areas, the native vegetation, both woodland and shrubland, has been thinned rather than cleared, again in the interests of agricultural activities. Interestingly, in the MDB is found one of Australia's main areas of 'tree increase', namely the Pilliga Scrub, as well as large areas of tree plantations (especially Pinus radiata) (see Forestry). Also, some people are beginning to question the extent and nature of the vegetation changes that have taken place (Ryan et al. 1995).

Continuing change

In spite of the many commendable efforts to preserve what is left of the native vegetation - for its own sake and for its contribution to the continuing viability of the Basin - land clearing has continued to take place. In fact, for Australia as a whole, as much land has been cleared in the last fifty years as in the 150 years before 1945 (Glanznig 1995). The situation in the MDB is unlikely to be different. For example, in the eight years to 1984-85, in the area covered by the St George, Goondiwindi and Moree 1:250,000 map sheets in northern New South Wales, over 627,000 hectares of native woody vegetation were cleared, nearly 70 per cent of what had remained in 1977. If such figures are extrapolated for the whole of the study area (by no means all of the wheat-sheep belt in NSW), over 300,000 hectares a year were cleared between 1977 and 1984-85 (Sivertsen 1994). In the wheat-sheep belt, it is estimated that less than nine per cent of the original vegetation cover now remains. Clearly, major changes in the Basin's natural vegetation are not simply a thing of the past, of the early years of settlement. In fact, with modern machinery, it is now very much easier to make such changes, the clearing of the Brigalow (Acacia harpophylla) communities in the Queensland part of the Basin in the 1960s and 1970s, as well as areas to the north, providing a classic illustration.

As in the past, much of the continuing change is the result of changing agricultural activities. The expansion of the cotton industry, both irrigated and dryland, has been a significant factor in such changes in the northern Darling Basin over the past thirty years. Australia's rangelands, which include much of the arid and semi-arid north-western parts of the Basin, present particular illustrations (Foran et al. 1989). In these areas, livestock grazing has been the major factor in changes to the native vegetation, not least in terms of the increasing problems of reduced quality pastures, woody weed infestations and associated soil erosion (QDPI 1993, 44-45) (see Agriculture, Irrigation and Land Degradation). Because of such problems, as well as the non-viability of many of the grazing activities, there are some people who believe the rangelands should be de-stocked and become a vast nature reserve.

Quite apart from the clearing of native vegetation, land use is constantly changing. The introduction of new crops and new farm management practices, for both crops and livestock, means that agricultural land use changes frequently. Crops such as cotton, rice, canola, and sunflowers are evident in terms of land use and their visual impacts. Agricultural and pastoral land is taken over for urban development, with Canberra providing perhaps the best illustration within the Basin. New roads, especially dual carriageways such as the re-built Hume Highway, are other important changes to land use. As for railways, the changes are now more often associated with their abandonment.

Land use today

In the continuing absence of a comprehensive survey, it is difficult to provide an accurate picture of land use in the Murray-Darling Basin. Further, at the scale available here, it is possible to provide only a very generalised map. A more detailed picture will have to await completion of the final stage of the 'Basincare' project (Ritman 1994 ). However, the Figure 1 and Table 1, supplemented by material in other pages, provide pictures or overviews (MDBMC 1987). The different categories and definitions that are used rule out direct comparisons between them, quite apart from the inconsistencies between the sources and data presented in other pages. However, these 'snapshots' provide a picture of land use in the Murray-Darling Basin that is dominated by grazing with relatively small areas devoted to other uses, though these are important regionally and locally (see Agriculture and Irrigation).

In detail, of course, the picture is very much more complex in all parts of the Basin, in terms of the present land use and the changes that have taken and continue to take place. Such changes are illustrated by the various photographs (see also, for example, Graetz et al. 1992).

The implications of changing land use

Overall, the most dramatic change in the Murray-Darling Basin's vegetation cover and land use is that from one of natural vegetation (though not unmodified) to agricultural landscapes. These changes have brought many obvious benefits and Australia's present society and economy would not exist without them. However, it is now realised that the changes have also brought many costs and we are increasingly aware of the consequences of "too much of a good thing", especially in terms of the many forms of land and water degradation and associated declines in agricultural productivity (see Land Degradation, Water Quality and Agriculture). It is also evident in the reduced habitat for many native fauna. For example, the decline of the Superb Parrot (Polytelis swansonii) in the south-east New South Wales portion of the Basin is largely due to clearing of box woodlands that provide forage and breeding sites for the birds (Figure 2) (Streatfield 1995).

Figure 2 Superb parrot distribution

Land clearing continues in parts of the Basin (Glanznig 1995), but measures are being taken to stop or reduce it, as in South Australia, where farmers have to obtain planning permission before they can clear native vegetation. Most applications are being rejected, but the State Government pays compensation for lost farm production. At the federal level, there is increasing pressure to halt land clearing. On a more positive note, large numbers of trees are now being planted, by numerous individual farmers and land owners and through numerous tree planting and re-vegetation programs (see Forestry). Some have government support; others are independent of such support. All are dependent on considerable community input, such as the River Murray Corridors of Green program and the 'Angry Anderson Landcare Challenge', which resulted in a major commitment to tree planting (Anon. 1995). Such activities are stimulating much independent and group tree planting. The reversal of many current land uses together with changes to land management practices are essential to the sustainability of the Basin and its many activities.

Conclusion

Land use change will continue to take place, in both the rural and urban areas of the Murray-Darling Basin. However, much greater attention must be given to such changes, now and in the future. The environmental and economic consequences of past and continuing changes, especially in the interests of agriculture, are now well documented (see Land Degradation and Water Quality). The continuing threat to biodiversity through such things as land clearing and feral animals, such as rabbits, wild pigs and goats, is a growing concern (Graetz et al. 1995). Now, it would appear that land use change and land clearing make a major contribution to total Australian greenhouse gas emissions (Barson et al. 1995). An overall assessment of land use and land use change in the Murray-Darling Basin is clearly needed.

References

AHC (1995): The National Wilderness Inventory. Australian Heritage Commission, Canberra.

Anon. (1995): "Thanks five million Australia!". The Challenge, December, 4-9.

Barson, M. et al. (1995): "Land use changes: a surprise in the National Greenhouse Gas Inventory". Search, 26(4), 122-125.

Carnahan, J. et al. (1990): Atlas of Australian Resources, Third Series, Volume 6: Vegetation. Australian Surveying and Land Information Group, Canberra.

Garman, D.E. (1983): "Water quality issues in Australia". pp. 1-265 in Water Quality Issues. Water 2000: Consultants Report No.7. Department of Resources and Energy, Canberra.

Glanznig, A. (1995): Native Vegetation Clearance, Habitat Loss and Biodiversity Decline. Biodiversity Series Paper No. 6. Biodiversity Unit, Department of Environment, Sport and Territories, Canberra.

Graetz, D. et al. (1992): Looking Back: the changing face of the Australian continent, 1972-1992. Office of Space Science and Application, CSIRO, Canberra.

Graetz, R.D. et al. (1995): Landcover Disturbance over the Australian Continent: a contemporary assessment. Biodiversity Series Paper No. 7. Biodiversity Unit, Department of Environment, Sport and Territories, Canberra.

MDBMC (1987): Murray-Darling Basin Environmental Resources Study. Murray-Darling Basin Ministerial Council, Canberra.

QDPI (1993): The Condition of River Catchments in Queensland: a broad overview of catchment management issues. Queensland Department of Primary Industries, Brisbane.

Ritman, K. (1994): Basincare: vegetation data for the Murray-Darling Basin. Land Information Centre, Bathurst.

Ryan, D.G. et al. (1995): The Australian Landscape: observations of explorers and early settlers. Murrumbidgee Catchment Management Committee, Wagga Wagga.

Sivertsen, D. (1994): "The native vegetation crisis in the Wheat Belt of NSW". Search, 25(1), 5-8.

Streatfield, S. (1995): The Superb Parrot. Murray-Darling Basin Commission, Canberra.

Walker, J. et al. (1993): "Ecohydrological changes in the Murray-Darling Basin. I. The number of trees cleared over two centuries". Journal of Applied Ecology, 30, 265-273.

 Table 1 Major land uses in the Murray-Darling Basin (source: Garman 1983)