by Malcolm McDonell
Measures of sustainability show Australia’s rural landscape is in poor shape. One popular movement to address the situation is ‘landcare’ – focussed on revegetation of the natural bush. Landcare that is focussed can be part of a sustainable future. Any plans to address the problem has to deal with soil, water and care of biodiversity of plants and animals.
I want to look at the temperate south-east corner of the land in Australia, the most user-friendly part from a productivity perspective, and with a point of focus on Adelaide at the tail end of this territory.
Historical and geographical considerations
We are challenged by lack of water – exacerbated by its variability. To make way for agriculture much of the land has been cleared of its vegetation cover. The aboriginal owners were swept aside quickly, and no regard was shown for their management ways. Australia has a different biotic assemblage to other parts of the world; Charles Darwin contrasted it with the northern biota – “Two distinct Creators must have been at work”. He was not aware, as we are, that Australia is a unique remnant of the Gondwana heritage.
The soils are poor. Geoffrey Blainey claims Australia is the “world’s great museum of soil deficiencies”. What soils we have are thin, and the practice of deforestation for agriculture has left soils exposed which were then able to be stripped by rain and wind. The outcome is that across much of the arable land of the country a large fraction of the topsoil is gone.
The early colonists struggled for many years to produce food sufficient for the colony. Eventually subsistence was achieved. And in time the agricultural export economy grew with wheat, wool, and later meat production. Today corporate agriculture is concerned with exports and shows little concern for the discussion of sustainability, (beyond the public relations considerations) but the conservation minded (‘greenies’) do. The conservation movement goes in two different directions.
Two streams of sustainability are apparent –
– firstly, the conservation of biodiversity; and
– secondly, organic agriculture (dealing with soil and water),
and these agendas can be in conflict – such is our enigmatic land! Native plants thrive in the poor native soils, and agriculture looks to build a rich soil profile for fertility and production. The two do not sit happily in the same immediate environment.
Sustainability 1 – Conservation of Biodiversity
All species have a right to existence each for its own sake, but some species would also have value for some qualities that we may never know – if they are driven over the brink to extinction.
Loss of species
The demands of agriculture saw large areas of land cleared, and so many plants and animals were under threat. Many species of animals and plants were actually driven to extinction – and many more are now endangered. Endangered species should be given the highest priority in our management of the land. We may yet not even know their utility value to an ecosystem.
European colonial society has made two mistakes in terms of the Australian environment. One is to regard the native bush as inferior and to seek to replace it. The other is to ignore aboriginal land management. Cultural attitudes are sentimental. In the late 20th century Australians saw fault with their earlier attitudes and turned in favour of ‘the bush’ but this sentiment is not discerning and it accepts a simple answer where more analysis is needed. So our attitudes to the bush are simplistic. Likewise our attitude to aboriginal ways has changed, and here also there is a lack of rational analysis, as yet we have not understood much of their knowledge.
In the management of our sprawling landscape some land is taken up for settlement, more is given over to agriculture and some is retained as reserves. This reserve land is maintained by a low maintenance methodology – as far as possible it is left alone. In the popular imagination this is seen as ‘natural’ and ‘like it was before colonization’, however those two are not at all the same.
Numerous writers have pointed out the way parts of the Australian landscape were constrained by aboriginal communities. Forests were controlled such that the land was like a park with lots of open space. Closed forest was not the norm at all. And when we talk about forests in this Australian context we are talking about forests of (predominantly) eucalyptus trees.
Although this perspective would not be new to students of environment, at the cultural level this is not readily accepted today, as we have come to think of our best reserves as the ones we leave undisturbed. However, the reality, it seems, is that to leave the land alone is to profoundly change it! I believe our problematic, bushfire prone reserve areas demand a stronger approach, to keep them appropriately in check.
We know that the forests were controlled in this way, but I do not think we know for sure why they were thinned. Some writers have (glibly?) speculated that it was done to facilitate hunting of kangaroos, but was that the only reason? From a modern perspective there is more to be said about eucalypts. European land use has made their presence unstable to the soil.
1. Eucalypts are fire-prone. Who would doubt it? They have flammable bark and flammable leaves and are ecologically adapted to thrive with fire – which drives out other species. The terrible destructive bushfires that happen at times even close to our cities are fires thriving on a eucalypt fuel-load – the devastating crowning fires in particular. In 2007 we saw huge forest-fires in Los Angeles and it is Australian eucalypts that are to blame. They are not good companions for a sedentary populace.
2. Eucalypts are thirsty. In many places around the world where there is a low rainfall eucalyptus trees have been planted. They have proven valuable in drying out a swamp, and have been used in that way in other countries. But in Spain they are removing them because of the aggressive deep roots which are killing off forests of cork-oak trees. Even in suburban plantings we can easily see that the amount of undergrowth under the trees canopy is minimal – they out-compete all others.
3. The impact of eucalypts on the ecology is detrimental to the rest of the flora. Tim Flannery says “they like to get rid of nutrients out of soils” and further: “there is maybe only a hundredth as much protein available in those ecosystems as was available in the earlier systems. So it’s an impoverished system which is stable to a certain extent – but not nearly as productive.”
If not eucalypts then what?
The vegetation of the 18th century was not ‘natural’ it was also interacting with human beings and an artefact – aboriginal farmland. It begs the question what was it like before human occupation (50,000 years ago)? Might it have been a Gondwana vegetation, not characterized by eucalypts at all? The landscape has certainly changed since then – it is only about 11,000 years ago since Australia was under the influence of an ice-age. We have some knowledge of individual species that were around in earlier eras, but no clear picture of the species at the time of first human settlement, and certainly not of the spread of species across the landscape.
For instance, a useful street tree of today is the White Cedar (Melia Azedarach) which is a subspecies of an Indian tree – possibly a Gondwana link. In the present day, other available local native species of trees include she-oaks, native pine and blackwoods, but there are not many other options from the current assemblage.
The answer in the early 20th century was to plant exotics – and slowly make a European and American (northern) species mix. The trees planted in Canberra during that era illustrates it – poplars, plane trees…etc. Do we go back to that option? I think the rationale for planting indigenous shrub species still stands. We can still do a lot with understorey plants. However these species are of course fire-adapted, as the companions of the eucalypts – subject to fire on a regular basis. Remove fire from the ecology and surely we change the ecology markedly.
The environmental demand to find an assemblage of plants that is stable in the long term with minimal management is elusive. Just what landcare bush structure can we put in place and maintain with a low manpower management system? (Meaning we can look after it by basically leaving it alone).
It might be that just as aboriginal people found they could not leave it alone, we cannot take that path either. Could it be that we keep a restricted population of eucalypts as was done in pre-colonial times? With our present day housing situation the forest maintenance might have to be done more with a chainsaw than with fire!
But this issue is not dealt with until we consider the situation of soil and water.
Sustainability 2.1 – Soil
Early colonial farmers cleared the land and erosion by wind, rain and running water carried a lot of soil away. We have to plant to look after our soil. This might be native plants but it must be successful – and might require exotic plants.
The challenge is not easy. Soil enrichment is antagonistic to native plants, so weeds may thrive the more. And runoff from rich soils may find its way into the creeks and dams – promoting algal blooms. This could even be a threat to endangered species in the creeks, estuaries and coastlines! So care must be taken.
As I have just been arguing, native vegetation, especially eucalypts, robs the soil of water, so less is available for agricultural needs. On the other side soil improvement, enriching the soil with fertilizer, (inorganic or organic) for the sake of agriculture means the water that runs off can be high in nitrogen and phosphorus, and thus make for algal blooms in the creeks and ponds. Certainly some endangered species of fish and/or crustaceans could be lost due to this effect.
Sustainability 2.2 – Water
Australia has a population now of over 22 million people. Two hundred years ago the population was ½ to 1 million according to anthropologists. The population of Australia needs food. Which is to say that we need agriculture, and agriculture needs water. (I am not talking about the agriculture that is focussed on exports).
In Adelaide water is problematic. The state is largely desert and semi-desert. The well-watered part – Adelaide and the Mount Lofty Ranges – is an area of about ten thousand square kilometres, and it is home to a population of over one million people. That is a population density comparable to Indonesia and France. It is a very different picture to the situation of the eastern states of Australia.
In the early 20th century the growing city of Adelaide recognized the need for more water resources. The problem was dealt with by accessing the Murray River. Since then utilisation and exploitation of the water throughout the Murray-Darling Basin means that there is no longer any summer flow in the river, and the reliability of winter flows is not assured. We might well lose the support of the River Murray and be forced again to utilise local rainfall.
In recognition of this matter the state of South Australia has built a desalination plant to make a backup supply of water. However the desal-plant is coal fired, and if called on to supply water it would make a very large carbon footprint – just at the time we are trying to reduce our carbon use for sustainability. The logical end of it is clear we have to maximise our capacity to harvest the yield of water from the rain that falls on the Adelaide Hills – the Mount Lofty Ranges from Cape Jervis to Mount Remarkable.
As we have seen eucalypts are not a good choice for hills where rain is to be collected. Neither is bare ground. We would do well to create an ecology that supports water harvesting. Trees for shade, cooling the understory, vegetation cover and layers of humus on the soil, making a sponge of soil, capable of holding soil and allowing it to travel slowly across the landscape – eventually to creeks, then to be stored in thousands of ponds and dams over the landscape.
From this point of view what is the right choice of species for the Adelaide Hills – which is the catchment for that much needed water? An understorey of local native plants might be good, but what is the climax species? I think it probable that we will need some imported species as well. It might be reliance on Australian natives like the Moreton Bay Fig which does quite well in Adelaide, but it might be that we should use some exotic species too, like the Mediterranean Oaks – ready to thrive in Adelaide’s winter rain and summer heat and aridity.
We should also plant to enhance rainfall! Some vegetation does induce rain as shown by the research of Lyons who noted the 30% better rainfall on the vegetated side of the rabbit proof fence in Western Australia. And it is widely accepted that loss of vegetation is a cause of the growth of deserts in Australia and elsewhere.
Further, some plants are claimed to be more rain attracting than others. For example, P.R. Sarkar directed, and with local support made a change-of-landscape plantation in a run-down area of rural India, by the use of oaks (Quercus species) and ferns (and others) for promoting rain and water retention in the organic materials in the soil. This project at Anandanagar (West Bengal, India) now has running rivers, where dry stream beds were 40 years ago. When water is such a key for the Australian landscape this type of approach should surely be the focus of trials and experiment.
We need to care for endangered plants directly, and we need to care for endangered animal species with suitable habitat – be it native plants or otherwise. We need to plant to care for soils – to stop soil erosion, which might also be done by native or exotic plants. And we need to plant to maximise our water yield – to make rain, to shade the soil and understorey, to create a spongy soil receptive to moisture.
In Adelaide today there is sentiment and there is rhetoric, but there is no commitment – there is not even any analysis – towards a plan which can deliver a sustainable environment for the generations ahead. I hope we can formulate a plan that makes for a healthy environment into the future.
1. Triumph of the Nomads, Geoffrey Blainey, 1975.
2. The Biggest Estate on Earth, Bill Gammage, 2012.