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The scene is of Mount Dromedary across Horseshoe Bay, Bermagui, on the New South Wales South Coast

Abuse of Our Farming Soils, Desertification, Erosion and Dust

By Graham Andrews

Farming methods threaten the soils they depend on. Even soil fertility is threatened by agricultural practices. Yet soils are the basis of our very existence; without food, without agriculture, we don’t eat. If land is overstocked, soils are abused, and every last bit of goodness is extracted from them. Then, when we can’t do anything with them, they are abandoned. This problem is becoming increasingly urgent as human populations increase.

On the earth right now, we have all the soil we are going to have in our lifetime. It can take a thousand years or more for soils to form to a sufficient depth to be useable. This makes soil one of our most precious resources. But I believe it’s also one of the world’s most abused resources, for which we have yet to find a satisfactory substitute.

Let’s consider what soils are, and let’s look at their demise.

Soils are not composed of just one or two ingredients. They are complex materials; each type of soil possesses different physical and chemical properties, and comprises a combination of many parts: elements, ions, minerals, organic matter, oxygen and other gases, water and inorganic material. Every cubic millimetre of fertile soil contains millions of: bacteria, fungi, worms, micro-­organisms, and other invertebrates. Soils are a mixture of all these things and more.

Because of their incredible biological activity, I would suggest that soils could almost be considered to be alive. But with intervention, it’s easy to kill them, to render them sterile, unsupportive of plants, and unproductive for agriculture. That’s the easy part. The difficulty is breathing life back into them.

Agricultural soils must contain sufficient moisture to combat periods of dry weather that can occur at any time of the year, and for any duration. When reserves are low, the growing season for plants, such as grasses or pastures, will be short, with insufficient feed available for livestock.

Effective water control is possible by taking proper care of the soil, maintaining a reasonable vegetation cover at all times, and ensuring a good reserve of humus.

During the next hundred years the United Nations reckons that the world’s population will have increased from the present seven billion people to possibly around fifteen billion. And, if the Australian Bureau of Statistics calculations, based on present rates of increase in population, prove to be correct, Australia’s population could rise from the present twenty-two million to well over forty million people in the same time. The people then will have to depend on the soil that is remaining. By the end of this century, there may not be much of the existing soils left.

Australia has been practising agriculture for just over two hundred years – in many parts of the country, it has been for only one hundred years or less, yet there has generally been a marked deterioration in soil structure, and fertility, and in the volume of soil remaining. The cost of replacing the minerals lost by the removal of the top few millimetres could well be in excess of one hundred dollars per hectare. The cost of nutrients lost from very fertile soils could well be ten times that amount. The loss of even a small amount of topsoil reflects heavily on the operating costs of farming.

A farm, neglected, with the soil blown away, or washed away year after year, will have a short life. Yet we have less soil in the world than we had one hundred years ago, less soil to feed an extra eight billion people in the next hundred years. The topsoil lost worldwide is now estimated by scientists at twenty­-five billion tonnes every year. Much of the cause of this soil depletion is drought, and wind, and poor farming practices spanning several farming generations. But the problem gets worse – not better. And many of these problems can begin with salt – that white menace that causes loss of soil structure, and loss of vegetation cover that would normally hold the soil together.  

Look at the dust storms that blow across continents. Australia has frequent storms that dim the sunlight. America has them. Other lands have severe storms that carry fertile soil and deposit it in the oceans. A dust storm can carry upwards of a million tonnes of topsoil – a million tonnes of fine, fertile soil. A million tonnes of fertile topsoil lost in an hour would have grown thousands of tonnes of feed for tens of thousands of animals, and feed for the people. That topsoil lost during a one-hour dust storm represents tens of thousands of tonnes in equivalent fertilisers worth perhaps millions of dollars – the cost to replace only the minerals lost. A quick loss indeed, and very expensive.

NASA’s satellite photographs of the earth show huge dust storms almost on a daily basis – millions of tonnes of soil dust blown across China, or across the Atlantic where the soil removed is not deposited back on to the ground, but lost in the oceans. Some dust storms have been so intense that visibility is reduced to a few metres. They can turn daylight into darkness.

Dust storms can change the atmosphere to yellow, or red, depending on the source of the dust – or, more correctly, the soil. Which country did it all come from? It could have been from just about anywhere, from any continent.

Loss of soil and soil fertility by erosion is not confined to lands in distant places. It occurs wherever soil is disturbed for agriculture. Losses from areas in the Darling Downs in south-eastern Queensland are estimated at up to one hundred tonnes per hectare – every year. The soils there may be deep, but I wonder how indefinitely can losses of this magnitude be sustained, and production maintained, at present rates of soil depletion?

The El Nino is often blamed for causing the droughts, but El Nino doesn’t cause the dust storms and the significant loss of soils. Blame inappropriate farming practices. Blame salinity that results from inappropriate farming practices. Blame deforestation. Blame overgrazing. Overgrazing during a severe drought results in loss of soils ... salinity … deforestation. But if you must blame something, you need to look further than El Nino.

Many people show a distinct reluctance to benefit from the lessons that should have been learned from the past. We’ve learned nothing from the desertification around the world ­estimated by some scientists to have increased by two and a half times during the last century alone. We’ve learned nothing from the dust storms that are becoming more frequent. We look at the thick clouds of dust over the continents and show no remorse, not appreciating that the cause of those dust storms is invariably our abuse of agricultural lands. Obviously, by our disregard and lack of remorse for those clouds of red dust, it seems that we don’t know what’s causing the problem. Perhaps we just don’t care.

The time will come when we must take action to overcome our abuse of the land that feeds the world’s population. But those who are well fed, with fresh meat on their tables, and meat in the refrigerator for their next meal, should not overlook the fact that the world is facing difficulties in feeding all the people on the planet. It feeds the wealthy, but many countries are struggling to adequately feed even a small fraction of their populations – even disregarding political situations in various parts of the world that exacerbate the problems of hunger. Perhaps Australia is lucky to feed its own population. With land that is constantly being eroded and worn out, how much longer can we support ourselves? And what of those people of other countries who are less well off?

At the height of a dust storm in Victoria during the early 1980s, the dust extended across the entire width of Victoria, and stretched many kilometres from North to South. The yellow cloud was over 300 metres deep when it struck Melbourne, but in other areas it extended thousands of metres into the atmosphere. Scientists estimated that about 50,000 tonnes of topsoil were stripped from the Mallee in western Victoria, with approximately 1,000 tonnes of it being dumped on the city of Melbourne, leaving the ground bare, and exacerbating the effects of the drought. On that single day in 1983, 50,000 tonnes of fertile soil was removed from Victoria’s agricultural system. And that was in only one day.

The New Zealand Alps on the South Island are often turned red, or brown, because of the loss of Australia’s topsoils that are blown across the Tasman.

Desertification around the world is not something that happened once, way back in history, and should now be forgotten. Our agricultural practices have increased the extent of deserts in the world from a little over one billion hectares in the early 1900s to more than two and a half times that area in about 100 years. That’s one and a half billion hectares taken out of the world’s farming system, yet the world’s population increased significantly during the same period. The deserts are increasing in size, because we are making them increase.

It’s a waste of time to plough sandy, infertile soils, to have the little that remains blow away in the first storm. It’s pointless to develop hillsides where one torrential downpour will – forever – remove the topsoil. It is a waste of time to develop pastures in those parts of a country where rainfall is inadequate to grow grasses. What last year might have been a ploughed field can, after heavy rains, consist of a series of deep erosion gullies. These are not productive; their loss to the farmer is appreciable; the inconvenience to the farmer is significant, and the cost to the country, enormous.

What can start off as a small gutter a few millimetres deep will, over only a few years, become a gigantic gully; square metres of erosion become square kilometres of erosion before very long. One square kilometre of land that has reached that final stage may not seem like much. Sometimes that area will total all the land on a farmer’s property. It happens that way. Frequently. It will remain only as a reminder of the better times that could have been won from that land, had the soil been treated with the respect that is essential if food production is to be maintained.

A thousand properties that have reached this stage of degradation add up to millions of dollars in lost profits and lost production, and hundreds of thousands of hectares of previously fertile agricultural land removed from production. The eroded land is abandoned. We look for somewhere else to initiate the same processes we used to destroy our previously farmed land.

A lack of vegetation allows winds to blow away much of the finer soil particles; wind carries them high into the air for considerable distances. As I said before, silt and dust from Australia is frequently observed in quantity in New Zealand. Soil blown by winds from the western portion of Australia can be observed far out over the ocean. Once the finer soil particles have been removed, what remains will be the hard clays, an impervious pan that will resist further wind erosion but this will be of little value to both present and future agriculture.

Wind erosion can be severe when fields are ploughed. Yet it is common to see dense clouds of soil blowing away behind a tractor, each year slowly but surely reducing the available soil. On cultivated land with little impedance to the flow of water, the rate of soil removal will be high. Down slopes, water erosion can be quite significant even over relatively short distances, and over short periods of time. Water can be concentrated into definite, well-defined channels with a still greater force with which to remove still more soil. Loose soil is easily broken down further, with particles being carried in suspension.

Yet, even a thirty percent cover of shrubs or trees, particularly in dry regions, is sufficient to greatly impede wind movement close to the ground. Substantial vegetation cover may be the only feasible method of preventing the initiation and continuation of the erosion processes. But... where are the trees?

Established trees seldom have a smooth surface under them. Trees drop leaves, small branches and litter on to the ground, which impede the flow of water so that it moves very slowly beneath them. Hence, the removal of soil particles is reduced. But ... where are the trees?

Salinity is an ever-increasing problem around the world. It is the rendering of large areas of once productive land barren so that no vegetation, no pastures, can grow there. The removal of trees often initiates soil salinity by raising the water table. Salt builds up in the soil due to inappropriate farming practices.

While the area of land affected in this way is large, the loss of productivity is serious. Losses caused by salinity result in economic losses of millions of dollars annually; that lost through other salinity problems such as seepage, even more.

The carrying capacity of much of the pastoral lands in Australia now is less than it was a century ago, despite the many millions of dollars that have been spent on efforts to improve productivity. The more we remove from the soil and the more we alter the soil’s structure, then the more work we will have do to breath life back into our soils. Only then will our soils again produce enough food for all of our people and all of our animals in sufficient quantities.

But that will take time, it will take energy, and it will take money.

Do you have the time to plant trees? Do you have the energy to organise information and events to spread knowledge of our soils widely in the Australian community? Do you have access to the ways government funds are allocated; for instance do you know anyone in government who you can influence to help to save our soils?