The Problem of Soil Erosion

WE ARE surrounded on all sides by soil. It is taken for granted by most people. But, since life on this planet could not exist without soil, it is sobering to learn that in just one country of southern Africa many millions of tons of soil are lost each year. And according to Dr. Kai Curry-Lindhal, UNESCO biologist and conservationist, the world soil loss during the past century was an estimated 2,023 million hectares (5,000 million acres)—about one quarter of the earth’s total farmland.

What causes such drastic loss of valuable topsoil so essential for life? Soil erosion.

What Causes Soil Erosion?

Erosion results from denuding the soil of grass or plants by overgrazing (too many cattle in an area) or plowing and leaving bare the topsoil, which is then blown away by wind or washed away by water. The mantle of soil on the earth is relatively thin, no more than 30 cm (12 inches) deep in many places.

Regarding the effects of erosion, the magazine Veldtrust, of August 1975, said: “The tragedy of South Africa has been the appalling rapidity with which its fertility reserves have been depleted and its thin soil covering washed away. In no other country have the disastrous consequences of erosion followed so quickly after its commencement.”

Farming has changed drastically in South Africa, as in most countries. In earlier years farmers would do what is called “subsistence farming”—they were concerned only with providing enough for their private needs. But as people became concentrated in towns the emphasis was on production. This led to what is known as “soil mining,” that is, exploiting the soil for a maximum return. As a result, the soil was overtaxed, causing the erosion problem that has now taken on national proportions. So man’s misuse of the soil over a long period has been the direct cause of this problem.

In Canada, the pulp industry has denuded huge forests. In Australia, the overgrazing by many millions of sheep has caused erosion. The same thing has happened in Iraq. Forage experts say that the pasturage in northern Iraq could support about 250,000 head of sheep, but there are at least a million grazing there. As civilization has spread, so has erosion.

But what does widespread erosion mean in practical terms? Are its effects overstressed, or does it really pose a threat to man’s continued existence?

The Extent of the Damage

Looked at from the point of view of the farmer, soil erosion means poorer crops, which, in turn, results in poorer feed for his animals. Both crops and animals will be more susceptible to disease and parasites, and this will further affect his production. If the situation goes unchecked, the time may come when his farm can no longer provide him with a livelihood.

Erosion also lessens the water supply in an area. Where there is plenty of vegetation, this helps to hold the water until it seeps into the ground; but where the land is exposed, the water tends to run off into the nearest river and carry with it much valuable topsoil. The fine silt gets to the sea, but the heavier silt is deposited along the lower reaches of rivers, gradually raising the riverbeds and resulting in more serious and more frequent floods. In South Africa, vast quantities of silt have been deposited in irrigation dams built by the State at great cost, and these dams could eventually be rendered useless.

The U.S.A. is also grappling with erosion. It is reputed to have nearly 250 million hectares (600 million acres) of agricultural land, but by 1940, 40 million ha (100 million acres) had been lost, most of it in this century.

Italy revealed to a conference held in Stockholm in 1972 that 80 percent of her grazing land in the Apennines and Alps was seriously damaged. Tanzania’s serious erosion problem has resulted in 30 percent of children under five years in the Dar es Salaam district suffering from malnutrition diseases. And Syria, the Congo, Kenya, Chile, India and many other countries face serious consequences as a result of soil erosion.

Erosion also acts like a catalyst in helping the great deserts to spread. In the last 50 years an estimated 650,000 km2 (250,000 square miles) of farming and grazing lands have been swallowed up by the Sahara along its southern edge, sometimes called the “Sahel.” In the Sahel more than 100,000 people have died as a result of drought and famine. Hundreds of thousands of tribesmen have lost their livestock and gone to refugee camps.

The problem is indeed serious and urgent, especially in the poorer countries. As their land becomes infertile, people move into towns and cities and put an extra strain on the food supplies there. The United Nations secretary-general, Kurt Waldheim, warned: “Countries could disappear from the face of the map. We risk destroying whole peoples in the afflicted area.”
These are shocking realities. But virtually all authorities on the subject agree on the cause—man’s unwise use of the land.

However, you may be surprised to learn that the natural process of soil erosion, when not aggravated by man, is actually a friend!

When Soil Erosion Is a Friend

The natural process of erosion by weathering, wind and water is very beneficial, as it breaks down rocks eventually to form soil. Without this process there would be no soil in which plants could grow, for soil consists largely of mineral grains that come from rocks.

Plants play an important role in keeping this erosion process under control. They tend to hold the soil in place and prevent rainwater from carrying the soil away. The plants trap the water so that it gradually seeps into the ground. Plants also help to contribute to the formation of soil, as their roots are constantly prying rocks apart, helping to grind them up into smaller fragments.
Animals also play an important part by helping to preserve the vegetation. This is well illustrated in South Africa, which used to have a large number of wild animals before man killed the majority of them off. Wrote James Clarke, in his book Our Fragile Land (pp. 69, 70):
“Every species had its contribution to make towards maintaining the soil cover, even if it was merely by donating its droppings or carcass to the replenishing process. Hippos played an important mechanical role by habitually walking away from a river in the direction of its flow so that when the river was in flood the rising waters would finger gently outwards—nature’s own irrigation system. Today, in most areas the hippos have been shot out and the banks of the rivers cultivated so that when the floods come they roll up the land and carry it off into the sea. Elephants had the habit of pushing trees into dongas [gullies]—a strange habit, but one with an obvious element of self-preservation in it, for it helped block the dongas and so they filled up, and as the land scar gradually disappeared the veld flourished once more. And elephants also had the habit of pushing over thorn trees so that they littered the veld. But each fallen tree effectively protected islands of grass from desperate grazers in times of drought. These specially protected grass nurseries would often be the only grasses left after a really severe drought and would seed the veld when spring winds and rains came.”

This is all evidence of a wise Creator who designed the earth and life on it in such a balanced way that everything would run smoothly. But man, by upsetting the balance of life designed by the Creator, has reaped the unpleasant results we see around us today. However, recently men have been trying to overcome the problem.

What Is Being Done

In South Africa, Soil Conservation Acts were passed in 1946 and 1969 to help farmers and encourage their cooperation with the State. As a result, many farmers have improved their farming methods, although there is still much to be done.

In many parts of southern Africa dry, windy weather occurs in winter when the soil is barren. To reduce loss of soil by wind, hedges or windbreaks are planted between arable strips to lessen its force. In some cases winter crops or fodder are grown to help keep the soil in place. The addition of lime causes adhesion of soil particles and also prevents or reduces the loss of soil.

Many farmers now practice contour farming—not plowing up and down slopes, but following the same level of terrain in and out of its contours or curves, thus preventing the furrows from acting as eroding water channels after heavy rainfall. Also, planting strips of grass down the slope of the land at suitable places helps the flow of water to spread and prevents erosive dongas. On some farms, watering the crops is not done by irrigation furrows that carry off topsoil but by spraying, or by other mechanical means. Further water control is achieved by constructing many small dams in valleys and on hill slopes; also, by putting rocks and branches in old dongas so that they get filled up and eventually are covered with grass.

Trying to raise too many animals in a certain area (overgrazing) is one of the main causes of destructive soil erosion. Control, not only of the number of animals, but also of their movements is important. Cattle have their own peculiar ways. If a herd has a long walk to water or to the kraal (cattle pen) for the night, they usually do so in single file and form deep tracks that become watercourses in heavy rains. So, where possible, many farmers now just let their cattle spend the night in the veld. They also provide smaller grazing areas with convenient drinking places so as to eliminate footpaths.

Man, too, needs controlling. In South Africa, it is a time-honoured custom to burn the veld in winter (to reduce ticks, pests, and so forth). But this causes a thinner grass coverage, resulting in more erosion. So this is now illegal in South Africa, except by permit.

Countries threatened by “desertification” have taken steps to halt the invading deserts. The people of Saudi Arabia have planted 10 million tamarisk, acacia and eucalyptus trees to save the al-Hasa oasis, near Hofuf, from the encroaching desert. They have also tried spraying the sand with a petrochemical “glue” that binds the grains together and prevents the sand from blowing away. The Libyans have tapped the so-called fossil water locked under the desert and have also made large circular patches of farmland in the Sahara desert with the aid of irrigation techniques developed in America. The Chinese have succeeded in growing new grasslands, vineyards, cotton and other crops in the desert area of Sinkiang.

The Israelis have restored water collection systems built by the ancient Nabateans in the Negev desert, and are using these to water orchards of almond and pistachio trees. Drip irrigation systems are also being used in the Negev, and these systems carry small quantities of water directly to the roots of plants, using computer monitors.

But there are still many setbacks facing those trying to save the environment from irreparable damage. The United Nations in 1977 called for international cooperation “on a scale not seen so far in the history of mankind.” Is such cooperation likely to occur? The meeting in Nairobi was marred by political ill feeling and disunity. One observer said: “So much political sniping and hollow hyperbole go on in open and closed sessions that you begin to feel that one of the greatest deserts is the human mind.”

Legislation by governments is not enough because it cannot change the selfish desires of men. To solve the problem of erosion, as well as the host of others facing mankind, it needs a completely new system of things, a new approach to problems and progress based on the great law: “You must love your neighbor as yourself.”Only the great Maker of this beautiful planet can accomplish such a change. Only he can restore the perfect balance of natural forces as at the beginning.