Down come the trees .....

The extensive clearing of land for agriculture and for rural development such as roads and towns was an integral part of economic development. There was the perception by Government and society that, for maximum productivity to be achieved, all land should have native vegetation removed. Trees were perceived to be competitors for pasture and space and the need to clear was a feature of conditional purchase settlement schemes. Failure to comply with clearing regulations could result in loss of the lease or failure to acquire the land freehold. Community pressure to clear was strong in the pioneering days. Settlers were not given any guidelines on clearing and were told to clear as cheaply as they could.

With the development of land for agriculture, clearing is unavoidable. Huge tracts of native vegetation have been cleared and in many shires in Western Australia's agricultural areas, less than 10 per cent of the original vegetation remains. Of the 25 million hectares of land in south-western Australia previously covered by native perennial vegetation almost 18 million hectares have been cleared. (Beeston et al. 1994)

In the 1960's the Government of the day was stating that the state was developing dramatically with a million acres (half a million hectares) of land a year being cleared/released. All these areas were all released with very little or no clearing guidelines. This lead to blanket clearing, two bulldozers pulling an anchor chain between them, dragging out all vegetation in their wake. As a result of this, land that should never have been cleared of vegetation, was cleared.

In 1986, legislation was introduced that required land users to notify the Commissioner of Soil and Land Conservation of any intention to clear land for a change in land use for any area greater than one hectare. At this time sections of the community were calling for a total clearing ban.

In 1995, the clearing regulations were widened to include nature conservation values to discourage any clearing of native vegetation and the onus was on the applicant to prove that the clearing would not lead to any further land degradation.

Apart from clearing for agriculture, other influences tend to reduce the amount of native vegetation:

• Tree loss caused by insects and fungi such as Phytophthora cinnamomi (dieback). This is a problem in forests that are disturbed or lack the original species composition;
• Grazing by domestic stock inhibits regeneration, because seedlings are eaten, trampled and broken;


• Increased frequency of fire will inhibit the growth of some species and encourage the growth of others, thereby dramatically changing the species composition;


• Rabbit plagues have led to the destruction of remnant vegetation and land degradation caused by rabbit warrens exposing the soil to the risk of wind and water erosion;


• Salinity destroys remnant vegetation;


• Weeds can invade remnants of native vegetation, competing with plants in the under storeys; and


• Mining in most cases destroys the ecosystem and some native species cannot be re-established.

The effects of vegetation decline

Loss of flora and fauna

Through clearing for agriculture, we have lost many plant and animal species. Since European settlement, twenty three species of plants, ten species of mammals, two subspecies of birds and one species of insects are presumed to be extinct in Western Australia and an even larger number of plant and animal species is considered endangered today.

Loss of genetic diversity

Within species and between species there are differences or variations. Maintaining this genetic diversity has been identified as an important aim of conservation strategies. In natural environments, populations of organisms with a high genetic diversity have the best chance of coping with unfavourable environmental changes, because at least some individuals will survive. The traits which enable the survival of these certain individuals may then be passed on to the offspring. Loss of diversity limits the ability of populations and even whole ecosystems to respond to environmental changes. It also represents a loss of genetic resources that may be useful to humans in the future. Loss of much of the native vegetation has led to an impoverishment of the genetic diversity, either by destroying complete populations or by drastically reducing their range.

Loss of nutrient cycling

Trees play a major part in recycling of nutrients. They can recover nutrients leached from the surface soil layers and nutrients produced by weathering of subsoils. The pastures and crops that have replaced much of the native vegetation cannot do this and fertilisers are needed to maintain soil fertility.

Land degradation

The loss of native vegetation has led to erosion and salinity. Once vegetation is removed, nutrient recycling is reduced and the land becomes prone to erosion. Without deep-rooted plants, more of the rainfall reaches the watertable, making it rise and cause salt problems on the surface.

What can we do?

Clearing of native vegetation has been banned in some catchments to protect water supplies. Protecting remnant native vegetation on farms is supported by Government policy and providing subsidies on fencing. Regeneration and maintenance of native vegetation by landholders should play an important role in halting its decline.

Education concerning the value of native vegetation and community participation in its management is vital. People who realise the value of native vegetation on road verges, for instance, are less likely to damage it. Local communities can help by preparing inventories of local reserves. Large tree planting schemes, through groups such as Greening Australia, allow people to become involved. Land conservation districts can be a focus of changing farmer attitudes to farming systems and can show the aesthetic, economic and conservation value of retaining native vegetation.

References:
Beeston, G.R., Mlodawski, R.G., Sanders, A., True, D., (1994). Resource Management Report, No. 149, pp 45.
Davies-Ward, E., and Finlayson, R., (1997) Environment Western Australia 1997 Draft State of the Environment Report for Western Australia, Department of Environmental Protection, p.63.

Next » | « Back to Index