Past sets limits for the future

The following article is reproduced from Nature Australia and informs dot points 1.2.4 and 1.2.5 of the VCE OES study. VOEA has provided discussion questions at the foot of the article.

by Mary White

To find out why land and water degradation is increasing, one has to appreciate that this ancient land has set the parameters within which sustainable use is possible.

Australia today faces serious problems of soil and water degradation. Our current land-use and agricultural practices are largely unsustainable. The more visible problems of ever-increasing salinisation of soils and rivers in the two major food-bowl areas - the Western Australian Wheatbelt and the Murray Basin - are receiving increasing media attention. Less publicity is given to acidification of soils (resulting in loss of productivity), and to high levels of nutrients in rivers (leading to algal blooms and other imbalances) due to excessive use of fertilisers and the use of legumes in pastures and crop rotations. Loss of structure and microbiological content of soils, and the hazards posed by the profligate use of pesticides and herbicides, rarely get a mention. The adverse long-term effects of irrigation, the dams and water diversions that are profoundly affecting, and even killing, some rivers, are seldom acknowledged. The widespread degradation that results from heavy grazing pressures, in fragile arid and marginal lands in particular, is largely ignored.

To find out why land and water degradation is increasing inexorably, one has to appreciate that this ancient land, because of its geological and evolutionary history, has set the parameters in which sustainable use is possible.

Australia is the driest continent, and arid lands of the world have proved to be extremely fragile. (Similarly arid lands of the Middle East, for instance, are now man-made deserts.) It is also the flattest and most poorly drained, with vast regions, excluding the margins, inwardly draining. As a consequence of its flatness it has accumulated sediment and is a land of vast floodplains. Its rivers have the most variable flow patterns of any in the world, and most of the arid and semi-arid regions that comprise 85% of the land surface are ephemeral. Floodplains are as much a part of the rivers as are the channels and banks, and failure to recognise this has led to widespread degradation. We now know that the health of the river ecosystems depends on the patterns of flood and restricted flow - the very features that our management and regulation have sought to eliminate.

Poor drainage of most of the continent has led to accumulation of salt, and saline watertables underlie much of the land, Upsetting the hydrology by removing perennial, deep-rooted vegetation, or by irrigating, causes rising saline watertables and salinisation.

Australia’s soils are almost universally thin, poor and easily eroded, made from deeply weathered rocks that have had many nutrients leached out of them through the ages. Only six per cent of the land surface is arable. The continent’s stable, mid-plate situation accounts for the absence of widespread volcanic activity and consequent soil enrichment. No renewal of soils by glaciation has occurred since the late Carboniferous ice age of nearly 300 million years ago. The Pleistocene ice age of the last 2.6 million years … brought extreme dryness and increased windiness in glacial stages. During the last glacial maximum 18,000 years ago, rainfall was half today’s amount, and more than 80% of the continent was affected by windblown sand. The major dune fields were established, as were the gibber plains and deserts. Recovery from that quite horrendous stage, when the Murray basin, for instance, was a salt desert, created the modern continent and its ecosystems to which Europeans came just over 200 years ago.

The ice-age history of northern hemisphere lands from which the settlers came was completely different from that of Australia. Great icesheets had ground across the lands, creating fresh, new, nutrient-rich soils, and then modern climates stabilised with predictable seasons. In contrast, Australia has an unpredictable climate due to ENSO, the El Niño-Southern Oscillation, which creates additional and often devastating problems of drought and flood. The agricultural and land-use practices suited to those northern hemisphere conditions were imported into Australia, whose histories and environments could not have been more different. The introduction of multi-millions of hard-hooved grazers has had disastrous consequences for grasslands, saltbush plains and the rangelands.

The incompatibility of inappropriate practices and foreign biota with our age-old, fragile land are now only too obvious. We currently feed the equivalent of 80 million people, and the rundown of our basic resources is reaching crisis proportions. Unless we change our ways and work within the limits set by the land, we will not have the viable resources to feed 20 million Australians in 2020.

Dr Mary E. White is a palaeo-environmentalist and author.

This article was first published in the Spring 2000 edition of Nature Australia and is reproduced here with permission.

Discussion Questions

1. Salinisation of soils and rivers are the "more visible" environmental problems affecting Australia’s two major foodbowl areas. List 6 other not so visible environmental problems mentioned in paragraph 1.

2. What three major geological and/or evolutionary features of the Australian continent (paragraph 3) have severely limited what humans can and can’t do without totally destroying the environment (i.e helped "set the parameters within which sustainable use is possible")?

3. List 2 factors that cause increased salinisation. (Paragraph 4)

4. What does the writer mean when she states that "Only six per cent of the land surface is regarded as arable."?

5. What 3 factors have contributed to Australia’s soils becoming (and remaining) "almost universally thin (and) poor"? (Paragraph 5)

6. How were things different in the northern hemisphere? (Paragraph 5)

7. Explain the following sentence: "The introduction of multi-millions of hard-hoofed grazers has had disastrous consequences for the grasslands, saltbush plains and the rangelands."

8. Australia has a current population of less than 20 million, yet "feeds the equivalent of 80 million people"? How is this possible? (Last paragraph)

9. What is the writer’s final conclusion?

10. Do you agree with that conclusion?

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