Before moving on to Cyprus and North Africa, let's look at China. Civilization here probably arose somewhat later than that in the Near East and was influenced by it. Mixed agriculture, irrigation, the oxdrawn plow, and terracing of slopes are notable similarities in the two regions (fig. 7).

Figure 7. -- These bench terraces in Shansi Province illustrate the extent to which some Chinese farmers have gone to conserve the remaining soil on their hillsides.

It was in China, where I was engaged in an international project for famine prevention in 1922-27, that the full and fateful significance of soil erosion was first burned into my consciousness. During an agricultural exploration into the regions of North China, seriously affected by the famine of 1920-21, I examined the site where the Yellow River, in 1852, broke from its enormous system of inner and outer dikes. As we traveled across the flat plains of Honan, we saw a great flat-topped hill looming up before us. We traveled on over the elevated plain for 7 miles to another great dike that stretched across the landscape from horizon to horizon. We mounted his dike and there before us lay the Yellow River, the Hwan Ho, a great width of brown water flowing quietly that spring morning into a tawny haze in the east.

Here in a channel fully 40 to 50 feet above the plain of the great delta lay the river known for thousands of years as "China's Sorrow." This gigantic river had been lifted up off the plain over the entire 400-mile course across its delta and had been held in this channel byhand labor of men -- without machines or engines, without steel cables or construction timber, and without stone.

Millions of Chinese farmers with bare hands and baskets had built here through thousands of years a stupendous monument to human cooperation and the will to survive. Since the days of Ta-Yu, nearly 4,000 years ago, the battle of floods with this tremendous river have been lost and won time and again.

But why should this battle with the river have to be endless? Any relaxation of vigilance let the river break over its dikes, calling for herculean and cooperative work to put the river back again in its channel. Then suddenly it dawned upon me that the river was brown with silt, heavily laden with soil that was washed out of the highlands of the vast drainage system of the Yellow River.

As its flood waters reached the gentler slope of the delta (1 foot to the mile), the current slowed down and began to drop its load of silt. Deposits of silt in turn lessened the capacity of the channel to carry floodwaters and called on the farmers threatened with angry floods to build up the dikes yet higher and higher, year after year.

There was no end to this demand of the river if it were to be confined between its dikes. Final control of the river so heavily laden with silt was hopeless; yet millions of farmers toiled on.

In 1852, the yellow-brown waters of the Hwang Ho broke out of its elevated channel to seek another way to the sea. It had emptied into the Yellow Sea, where it had usurped the old outlet of the Shai River.

This time the river broke over its dikes near Kaifeng, Honan, and wandered to the northeast over farm lands, destroying villages and smothering the life out of millions of humans, and discharged into the Gulf of Chihli, 400 miles north of its former outlet. In its rage it had refused to be lifted any higher off its plain. Hundreds of thousands of farmers had been defeated. Silt had defeated them, valiant as they were.

Silt - silt - silt! We determined to learn where this silt came from, even up to the headwaters.

In a series of carefully planned agricultural explorations we discovered the source of the silt that brought ruin to millions of farmers in the plains. In the Province of Shansi we found how the line of cultivation was pushed up slopes, following the clearing away of forests. Soils, formerly protected by a forest mantle, were thus exposed to summer rains, and soil erosion began a headlong process of destroying land and filling streams with soil waste and detritus.

Without a basis of comparison, we might easily have misread the record as written there on the land. But temple forests, preserved and protected by the Buddhist priests, gave me and my Chinese associates a remarkable chance to measure and compare rates of erosion within these forests and on similar slopes and soils that had been cleared and cultivated.

In brief, my Chinese scientific associates and I carried out a series of soil-erosion experiments during rainy seasons of 3 years. In these experiments we measured the rate of runoff and erosion by means of runoff plots within temple forests, out on farm fields under cultivation, and on fields abandoned because of erosion. For the first time in soil-erosion studies, we got experimental data for such comparisons. Here too, we found how the Yellow River had become China's Sorrow, for we found that runoff and erosion from cultivated land were many times as great as from temple forests.

It was clear that if the farmers of the delta plain were ever to be safeguarded from the mounting perils of the silt-laden Yellow River, the source of the silt must be stopped by erosion control.

Farther west in the midst of the famous and vast loessial deposits of North China, we found in the Province of Shansi that an irrigation system first established in 246 B. C. had been put out of use by silt. Here again silt was the villain.

We sought out the origin of the silt that had brought an end to an irrigation project that had fed the sons of Han during the Golden Age of China. This origin was found in areas where soil erosion had eaten out gullies 600 feet deep (fig. 8). It was while contemplating such scenes that I resolved to challenge the conclusions of the great German geologist, Baroon Von Richthofen, and of Ellsworth Huntington that the decadence of North China was due to desiccation or pulsations of the climate.

Figure 8. -- These huge gullies indicate the severity of soil erosion in the deep, and once fertile, loessial soils of northern China. Millions of acres have been cut up like this and are now almost worthless.

Temple forests gave the clue. They demonstrated beyond a doubt that the present climate would support a generous growth of vegetation capable of preventing erosion on such a scale. Human occupation of the land had set in motion processes of soil wastage that were in themselves sufficient to account for the decadence and decline of this part of China, without adverse change of climate.

It was in the presence of such tragic scenes on a gigantic scale that I resolved to run down the nature of soil erosion and to devote my lifetime to study of ways to conserve the lands on which mankind depends.

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1/ T.I. Li, C.T. Ren, C.0. Lee, and others. See Proceedings of the Pan-Pacific Science Congress, Tokyo.1926.