' U. S. Soil Conservation Service. 192 UNIT III SECTION 9 LIFE IS INTIMATELY CONNECTED WITH CHANGES IN THE EARTH'S SURFACE Where there is no vision, the people perish. — Proverbs 29:18. What shall it profit a nation to gain all the gold in the world and suffer the loss of its soil? — Walter G. Lowdermilk.^ Introduction. The natural endowment of the United States is unrivaled among the nations of the world. One of the largest of the favorable climatic regions is found in the United States. Almost one fourth of the land suitable for cultivation within the temperate zones lies within the boundaries of continental United States. This Section presents a "get-rich-quick" version of this "paradise lost." The average uninformed person is likely to consider soil as just plain dirt, not realizing that it is the connecting link between the living and nonliving world. The early pioneer, confronted by seemingly inexhaustible resources of plant and animal life, killed huge herds of buffalos for their hides, ruthlessly cut down the world's greatest forests and burned the wood to obtain charcoal or wood ashes, as if these natural resources were man's worst enemies. Sod which had been thousands of years in the making was plowed up with considerable difficulty; and as soon as a piece of land was denuded of its soil, the plows moved on to new virgin territory. By this time, however, the machine age had multiplied man's destructiveness a thousandfold, so it was not long until the scene of the marvelous golden wheattields in the Middle West became the desolate graveyard of the machines which made the wheatfields possible and the dust bowl witnessed the exodus of some of our best citizens, who had unwittingly helped to bring about the permanent loss of an alarmingly high per cent of the soil which is our priceless heritage.
LIFE IS DEPENDENT UPON EARTH CONDITIONS 193 Land Plant Life Requires Moist Soil. Plants must have soil into which they may send their roots for anchorage and from which they may secure the water and soluble minerals essential to their growth. Soil is therefore the most important geological product that is essential to life. Soil Is a Product of Erosion or Volcanic Action. Most of the soil is produced from rocks by the various processes of erosion. They are first broken into small pieces by the various disintegrating agents. Plants could not grow, however, even in finely powdered Fig. 59. Plowing on the prairies beyond the Mississippi. (Sketched by Theodore R. Davis.) Six strong oxen were required to pull this plow which is turning over the thick virgin sod of the Great Plains. The pioneer's plow destroyed the luxuriant tall grasses of the Great Plains where the buffalo grazed. (Culver Service, New York.) rock. Chemical changes must take place in the disintegrated rock before it is suitable for plant growth. Oxygen and carbon dioxide of the air, supplemented by other substances, such as nitric and sulfuric acids, which are produced in the air by lightning, volcanic activities, etc., decompose these rocks. Even then the decomposed rock particles will not support plant growth. Nature's chemists, the bacteria, must now go to work. Microorganisms can live and multiply in water. Some of them can live without oxygen. Some of them liberate sulfur from the compounds, others