Destructive erosion on an unwisely cleared slope in the Blue Ridge part of the southern Appalachians

A.-Wind erosion, the result of drought and trampling, New Mexico. Excessive concentration of cattle near permanent water during drought periods results in serious trampling. Wind has removed 5 or 6 inches of soil, exposing the roots of the few remaining plants to desiccation

B. Fire has destroyed the vegetation, and the steep slopes are rapidly washing away (California)

A.-A barren waste. Smelter fumes have destroyed the vegetation (Arizona)

B. All the herbaceous vegetation has been destroyed by overgrazing. The brush and timber are insufficient to prevent serious sheet and shoe-string erosion and excessive soil deterioration

What would be the feeling of this Nation should a foreign nation suddenly enter the United States and destroy 90,000 acres of land, as erosion has been allowed to do in a single county? Any American of live imagination knows that the people of the United States would willingly spend $20,000,000,000 or as many billions as might be necessary, to redress the wrong. Because rain water was the evildoer in this instance, which is but one of many, is the act forgiveable and is there no occasion for concern about it?

It is not necessary to go to China or to some other part of the world for examples of what eventually happens to unprotected slopes of cultivated areas. There is an abundance at home, not yet so vast in area as in China, but just as bad, and by no means small. It is well to observe, however, that millions of human beings have been driven out of the wasted uplands of China into the valleys of the great rivers, where the population is so dense and the land so completely used that even the roots of grain crops are dug for fuel. China cut the forests from the uplands and made no provision for protecting the bared slopes. Erosional débris sweeping out of these wasting highlands has rapidly extended the river deltas and made floods ever more difficult to control. After 4,000 years of building dikes and digging great systems of canals, the Yellow River broke over its banks and brought death to a million human beings during a single great flood. During one flood that great river, known in China as the "scourge of the sons of Han," changed its channel to enter the sea 400 miles from its former mouth.

No one, of course, wants anything remotely like this to take place in this country, but "coming events cast their shadows before." That the greatest flood of which we have reliable records came down the Mississippi in 1927 was a prophetic event. G. E. Martin's statement (14) about erosion as an enemy to agriculture "It is very unlikely that any other industry could suffer such severe losses and survive" is prophetic. That bare land at the Missouri Agricultural Experiment Station was found to be wasting 137 times faster than land covered with bluegrass, on a slope of less than 4 per cent gradient, is prophetic. That many millions of acres of cut-over land lie bare and desolate and exposed to the ravages of fire and erosion, with but pitifully little done toward reforestation, is prophetic. That minimum estimates show that the rate of plant-food wastage by erosion is twenty-one times faster than the rate at which it is being lost in crops removed, is prophetic.

These shadows are portentous of evil conditions that will be acutely felt by posterity. Shall we not proceed immediately to help the present generation of farmers and to conserve the heritage of posterity?

The writer, after 24 years spent in studying the soils of the United States, is of the opinion that soil erosion is the biggest problem confronting the farmers of the Nation over a tremendous part of its agricultural lands. It seems scarcely necessary to state the perfectly obvious fact that a very large part of this impoverishment and wast age has taken place since the clearing of the forests, the breaking of the prairie sod, and the overgrazing of pasture lands. A little is being done here and there to check the loss-an infinitesimal part of what should be done.

PART 2. SOIL EROSION ON WESTERN GRAZING LANDS

By W. R. CHAPLINE

INTRODUCTION

The toll the West has paid to soil erosion is enormous. Countless slopes, once covered with rich soil and a dense carpet of herbaceous and browse plants capable of profitably supporting millions of cattle and sheep, have been so wasted by sheet and gully erosion following depletion of the vegetation that they can now support far less than half the number of livestock that once grazed upon them. Furthermore, the loss of the valuable surface soil and the exposure of the less productive subsoil have made difficult the reestablishment of an abundant stand of plants. Fertile valleys, their good soil cut away by silt-laden flood waters or covered with sand and gravel, have had their value seriously impaired or have even had to be abandoned. The silt has finally been carried to the mouths of rivers to clog channels and hamper navigation.

Water available for agriculture, power, and industry will largely determine the development and prosperity of the West. In 1920 approximately 19,000,000 acres in the West were under irrigation, and it was estimated that this area could be extended to 51,000,000 acres by the conservation and development of the entire water supply (10). Erosion, however, is already endangering established projects and making prospective ones uncertain. A more adequate protective covering is necessary to safeguard these watershed interests.

Erosion, the removal of the soil cover by water or wind, is taking place everywhere, but under favorable conditions nature starts at once rebuilding the soil from the decomposition of rocks or by the addition of humic material from decaying vegetable matter. Numerous factors, of which climate, soil, topography, and geologic formation are doubtless the most important, influence these processes, but the vegetative cover is the main single controllable factor. It is recognized that forest cover furnishes the greatest protective value for preventing erosion and soil washing and for regulating stream flow. It is, therefore, important that forest growth, including its understory of herbaceous and shrubby vegetation, be maintained wherever possible at the headwaters on all streams used for irrigation, power, or navigation. West of the one hundredth meridian, however, forests grow on only 13 per cent of the land area. It falls to herbaceous and shrubby vegetation to afford the necessary protection to the soil and stream flow on the remaining 87 per cent. It is this vast area of unforested land that largely supports the range livestock industry which in turn plays a principal part in the prosperity of the West. On these western ranges the protective cover of vegetation varies from a very sparse stand of browse and