Soil Erosion – A Vicious Cycle
In The Land Deterioration Problem
(Page 1)

Soil erosion is both a contributor, as well as an outcome of land degradation. Hear we learn from Professor Nils Nykvist about the vicious relationship that exists between the two.

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By Professor Nils Nykvist

The beginning of the problem

Before humans started to influence nature on a larger scale, most of the land was covered by more or less dense forests. Of course, it cannot be excluded that more open grasslands also existed, created by fire and large prehistoric herbivores (it is known that large herbivores lived in North America before humans crossed the Bering Strait [11]).

Then about ten thousand years ago when the people in western Asia (the Fertile Crescent) began to cultivate the soil and engage in animal husbandry, a depletion of vegetation on a large scale began. The loss of biomass led to a lower formation of organic substances through photosynthesis, providing lower amounts of soil organic matter, which is of great importance for the storage of water and nutrients in the soil.

In fact, the largest population increase and hence the greatest impact on land occurred in areas where the climate was most favorable for humans.

Erosion of precious land

Due to this deterioration of soils, the vegetation cover decreased and left the soil more open for water and wind to detach and carry away the soil particles to lower-lying areas, where they were deposited (Fig. 14). In drier areas wind could also carry away soil particles and deposit them when the wind speed decreased (Fig. 15). Figure 14. Soil eroded from the slope has been deposited in a small depression. The Usambara Mountains, Tanzania.

Figure 15. Wind Erosion. Khartoum, Sudan.

The devastating effect of wind erosion on the American prairie, when half the U.S. was covered by a thin layer of soil, is very vividly described by John Steinbeck in the novel "The Grapes of Wrath".

The Greek philosopher Plato was the first to describe, as early as 400 BC, the deforestation and the resulting erosion of soil. In the publication Critias he wrote, ‘For some mountains which today will only support bees produced not so long ago trees which when cut provided roof beams for huge buildings whose roofs are still standing. And there were a lot of tall, cultivated trees that bore unlimited quantities of fodder for beasts. The soil benefited from an annual rainfall which did not run to waste off the bare earth as it does today, but was absorbed in large quantities and stored in retentive layers of clay, so that what was drunk down by the higher regions flowed downwards into the valleys and appeared everywhere in a multitude of rivers and springs. And the shrines which still survive at these former springs are proof of the truth of our present account of the country” [12, p. 134].

The impact of soil erosion

The soil that eroded down from the hills of the Mediterranean flowed into the sea or was deposited in the valleys, where marshes were formed when the soil hampered the drainage.

See the references for this article.

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