Suffering the Scourge of Salt

By Awake! writer in Australia

SALT is essential to human and animal life. It makes up nearly 1 percent of our body. We use it in food, medicines, and livestock feed. In fact, the world consumes some 190 million tons of salt each year. * But this useful and abundant substance is becoming a scourge to some of the world’s most productive farmland.

Some 40 percent of the global food harvest comes from the 15 percent of the world’s cultivated land that is irrigated. Indeed, channeling water onto seemingly barren land can make it blossom like the proverbial rose. But irrigation can lead to a buildup of salt residue in the soil, resulting in a slow poisoning of the ground. Already crop production is stunted by salinization on half of all irrigated land in the world. Indeed, an area more than twice the size of Switzerland is said to be lost every year as a result of salinization and waterlogging!

In his book Out of the Earth, Daniel Hillel, a prominent soil scientist, sounds this warning: “Each and every one of the insidious man-induced scourges that played so crucial a role in the deaths of past civilizations has its mirror image in our contemporary world . . . but on an ever larger scale.” Salinity is already said to be costing the U.S. economy five billion dollars a year in crop losses. Yet, there are few places on earth where this man-induced scourge is more menacing than Australia.

The White Death

Each hour, the vast wheat fields of Western Australia are losing an area the size of one football field to salinization. Dr. Tom Hatton of the Commonwealth Scientific and Industrial Research Organization (CSIRO) says: “Without question this is the largest environmental crisis we face.”

 The agricultural heartland of eastern Australia, known as the Murray-Darling Basin, is especially vulnerable to salinization. The basin covers an area as large as France and Spain combined, and it contains three quarters of Australia’s irrigated land. Close to half of Australia’s total agricultural earnings come from here. The Murray and Darling rivers, the arteries that feed this agricultural heartland, nurture thousands of wetland areas and supply drinking water for three million people.

Sadly, 750 square miles [2,000 sq km] of this vital land is already badly affected by salinization, and scientists estimate that a further 4,000 square miles [10,000 sq km] are at risk during this decade. The salt content is rising in the Murray and Darling rivers and their tributaries, and in some areas the water is becoming unsafe to drink. In the fertile fields that flank these rivers, salt-encrusted, lifeless bogs are forming. Farmers call this phenomenon the white death.

However, more than farmland is at risk. Scientists at the CSIRO warn that because of salinity, up to a thousand Australian plants and animals are threatened with extinction. Also, if things continue as they are, perhaps half the bird species in the Murray-Darling Basin will be lost in the next 50 years. Consider the lack of foresight that has provoked this environmental crisis.

The Source of the Salt

Scientists surmise that much of Australia’s salt came from ocean mist, carried inland over millenniums of time. The salt from the mist was deposited on the land by rain. Another source, they believe, is the salt residue of seas that once covered parts of the continent. Rain leached the salt through the layers of soil, and groundwater tables slowly formed below the salty subsoil.

Over time, eucalyptus trees and other vegetation carpeted the continent, growing roots that penetrated as much as a hundred feet [30-40 m] or more into the earth. The vegetation intercepted most of the rain falling on the soil and pumped it back to the surface, where it transpired from leaves. This kept the groundwater tables deep underground. But European farming methods, which brought prosperity and progress to Australia, also involved clearing vast tracts of  land. On account of mass removal of these pumplike trees, as well as the widespread use of irrigation, water tables rose. Thus, long-dormant salt has been dissolved and carried ever closer to the fertile surface soil.

Causes of the Salinity Problem

Controlled flood irrigation of crops boosts production in the Murray-Darling Basin. At the same time, however, this practice rapidly raises the groundwater tables under the fields. The salty groundwater then seeps into the river systems, polluting the fresh water. This creates another problem known as river salinity. The salty river water is pumped back onto the irrigated fields, and the problem increases in a vicious circle.

More insidious, though, is the form of salinity known as dryland salinity. Throughout the basin, deep-rooted trees have been replaced by pastures and annual crops, whose roots only penetrate a few feet into the soil. The rainfall previously absorbed by the trees now filters past the reach of the crops.

As a result, scientists estimate that from 10 to 100 times more water now seeps into the groundwater table than when trees were growing on the plains. So much extra water has soaked into the earth over the past hundred years that water tables under the Murray-Darling Basin have risen in places by up to 200 feet [60 m] or more. As these salinized water tables reach within a few feet of the surface, the farmer’s woes begin.

Fields once fertile begin showing areas of stunted growth. Long before salt-encrusted patches start forming, salinized groundwater lurking close to the surface is drawn upward by evaporation. At first, the plants growing on these patches can cope, but as more salt is drawn up and concentrated in the surface soil, the ground becomes infertile.

Dryland salinity affects more than just the farming community. It is already undermining some state highways, reducing their life expectancy by 75 percent. Also, it is damaging buildings, plumbing, and sewerage systems in country towns throughout the Murray-Darling Basin.

Is Recovery Possible?

It seems that the majority of these salinized water tables will continue to rise for the next 50 to 100 years. One report states that by the time a baby born today reaches the age of 30, an area the size of the state of Victoria​—about the size of Great Britain—​will be ruined. What is needed to turn back this destructive tide?

“We need to radically change the management and use of [Murray-Darling] Basin resources in order to maintain healthy ecosystems and productive land use,” states a government report. “Significant costs will be incurred . . . However, these costs are dwarfed when compared with the inevitable costs​—economic, environmental and social—​if current management practices are not changed.”

Large-scale tree planting would start to reverse the damage, but at present this is not seen as a profitable option. One scientific report noted: “We cannot return to conditions identical to the natural system. In many cases, improvements [from planting trees] would occur very slowly, if at all.”

In the meantime, farmers are being encouraged to plant crops that have deeper roots or to change to salt-tolerant crops. Some entrepreneurs are even mining the salt that has ruined their farms and are making a living from this enterprise. Others are planning to use salinized water ponds to raise ocean-going fish, prawns, and even seaweed commercially.

Australia’s experience is not unique. Unless major changes take place soon, the description of ancient Greece by the Greek philosopher Plato will sound ominously prophetic: “What now remains of the formerly rich land is like the skeleton of a sick man, with all the fat and soft earth having wasted away and only the bare framework remaining.”

[Footnote]

^ par. 3 The most common form of salt is sodium chloride. Other important salts are potassium chloride and ammonium nitrate.

[Map on page 25]

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MURRAY-DARLING BASIN

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Map: Mountain High Maps® Copyright © 1997 Digital Wisdom, Inc.

[Pictures on page 25]

Salt residue clings to the remains of a tree in the middle of a waterlogged field

Once fertile fields are killed as salt accumulates in the surface soil

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© CSIRO Land and Water

[Pictures on page 26]

First signs of the scourge​—infertile patches amid fertile fields

Salt drawn to the surface kills vegetation

The effects of salinity on once productive farmland

The final effects of rising groundwater tables

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All photos: © CSIRO Land and Water