DESERT DUST THAT GIVES CHINA LIFE AND DEATH.

Otago Witness, Issue 3511, 28 June 1921, Page 52

DESERT DUST THAT GIVES CHINA LIFE AND DEATH.

Although millions of Chinese are just now starving, that is a matter of defective transportation. The great plain of China, continues to be the richest farming land in the world. Every few years other millions perish in the floods of the Hoang, or Yellow, River. It is interesting to know that the loess, or fine silt, which makes the fertile plain and incidentally causes the floods by forcing the river to build itself above the land-level, comes by air route from the great desert of Gobi. Tt is this wind-blown desert dust that is at once China’s joy and China’s sorrow—the source of her food supply and the destruction of her population, in an article entitled “The Dust of Uobi” Jacques W. Redway gives us particulars in Ecology (Brooklyn, N.Y.). He writes : “The great plain of China, one of the most productive regions on the face of the earth, is not much larger than the semicircle of t-he Gulf States. Yet it supports 200 million human beings—about twice the population of the United States. Except for bosses of rock, remnants of the original surface, that protrude above the sea of alluvium, the plain is so flat that the earth’s curvature may be determined therefrom. “Fierce desert winds, black with their loads of rock-waste, have filled the old valleys and canyons of desert-Mongolia with coarse detritus worn from mountain crests and scarps. The onset of a simoom is a dense black cloud of dust—coarse, medium, and fine. The heavier dust can not be carried high above ground, and does not go far beyond the desert, since the wind slackens materially at the desert boundary. The lighter dust, being carried high into the air, reaches the great plain, and in some dust-storms even reaches the coast. The air is thick and glistening with yellow dust; and sometimes as much as one-tenth of an inch settles on the ground after a- severe duststorm. “The erosion that attends rains, and the natural tendencies of gravitation, move the dust toward the various river channels. The Yangtze, because of its swifter current and of not receiving so great a volume of dust, is able to carry all that is dumped into it. The. Hoang and its chief tributary, the Wei, receive far more than they can carry, and from time to time have broken their banks and have spread their sediments all over the great plain. The sediments spread by the floods of the Hoang now cover the plain very deep, in places exceeding 1000 ft. Gentle winds tend to spread the dust mantle evenly, while the forces mentioned above tend t,o clear it from the high spots and carry it to the low. The greater depths of loess, therefore, are in the river valleys. “Where the current of the river is swift enough to cut into the loess, the water has carved into the deposit, lowering its channel and leaving vertical banks of 10ft, 20ft, and 30ft or more in height. Among the Chinese the economy habit is always prominent. Dwellings built on

the flood-plain would cover ground that ? might produce foodstuffs. So the patient I farmer tunnels, and burrows, and exca- j vates into the hank of loess, making not only dwellings, but village communities in tho banks. The troglodyte population of j the flood-plain is very large. i “Physically, the loess is the lightest of 1 the wind-blown dust; therefore it is the j most easily' moved, and likewise it is ! carried farthest by the winds and the water. In cultivation, a man’s strength is sufficient to drag the primitive plough th rough it and to turn the furrow to the necessary depth. Here human strength performs the labour for which animal or mechanical force is necessary elsewhere. In spite of intensive cultivation, the ground is in a condition of almost- perpetual fallow. ® “In composition, the loess consists mainly of ferruginous clay, fine sand, potash, lime, P.nd nitrogenous matter. The last is derived from the grass and reeds which, while growing, are covered up by successive additions of wind-blown dust-. \V hat better material for soil can he found anywhere in the world? In many places three crops of grain are grown each year on loess soil. Perhaps the soil of the Nile delta and the lower Mississippi may be capable of supporting aa dense a population as that of the great plain of Chona, but neither can surpass it in productivity. “Phe dust burden delivered to the Hoang is born of the desert region to the north-westward. The winds spread it over the upper water-shed ; wind, rain, and flood in concert spread it over the great plain. The deposit of sediment is greatest in winter, when the volume of water is lowest. With the advent of the spring rains there is a volume of water of flood proportions that is treacherous, tempestuous, and at times overwhelming.” The Hoang is the largest river of northern China, Mr Redway goes on to tell us. The Nile poss'-bly excepted, it has been more intimately connected with the economics of the world than any other river. According to the Shu-king, the Books of History' edited by Confucius, a most destructive flood followed the bursting of the levees of the river about 2200 B.C. Tho work of restoring the revetments and adjusting the channels to the volume of the water made the name of the engineer, Ta-yu, famous for all time. He used practically- the method adopted bv the engineers of the Mississippi River Commission—namely, the adjustment of the velocity of the current to the maximum load of silt which the water carries. Mr Red way continues: “The hydraulic engineer of to-day accomplishes this by impounding the excess of water during flood seasons and releasing it during seasons of drought; Ta-yu accomplished the same result by the construction of additional channel's. In the lower part of the plain nine additional channels were constructed. Any number or all of them could be thrown open to a flood; any number of them might he closed as necessity- demanded. Thereby a uniform volume of water and a constant velocity of the current were insured. It was a task of 13 years. “Unfortunately, the wise plans of Ta-yu have not always been followed by his successors, who merely built embankments where high waters threatened overflow. When a stream can not carry the siltwhich ; t holds in suspension, the silt drops to the bottom and sides of the stream-bed, thereby building the bed and banks higher and higher. In 1844 Abbe Hue, a distinguished missionary and geographer, noted that throughout the greater extent of Honan and Kiang-su provinces the river-bed was materially higher than the plain—in places as much as 25ft. Within the period of written history the Hoang has changed its channel nine times. Within a period of 1000 years the Hoang has drowned more human beings than have been slain In all the wars of the same time. “Diking and channeling after the mans of Ta-yu might have been a great preventive of the disasters which have attended the floods of the Hoang, but a greater preventive must be found in the reforestation of the denuded slopes bordering the valley. The railwav engineers have already begun this work in a small way, but a measure of the sort requires national effort and control ; moreover, nearly a centurv of time will he required to make it effective. The, destruction of forests and protective vegetation has been China's great offence against Nature, and Nature has avenged herself by the Wuruction of the offenders. “In spite of Jo loss of lives by the million, and the destruction of property the value of which must tie estimated by the. billions of taels, tile floods of the Hoang are not an unmixed evil. Every flood has covered the great plain with fresh soil that is full to the brim with nutrition—and nutrition is life. Birthrate is the measure of nutrition ; and for every life that has paid the penalty of neglect, more than a life has been added. Life is in proportion to the richness of the soil. Tire coal and the iron-ore deposits of China are the richest in the world), butt the Idfustb of tiro Gobi is richer.”