The five indispensably essential materials in our civilization are wood,
water, coal, iron, and agricultural products.
We have timber for less than thirty years at the present rate of
cutting. The figures indicate that our demands upon the forest have
increased twice as fast as our population.
We have anthracite coal for but fifty years, and bituminous coal for
less than two hundred.
Our supplies of iron ore, mineral oil, and natural gas are being rapidly
depleted, and many of the great fields are already exhausted. Mineral
resources such as these when once gone are gone forever.
We have allowed erosion, that great enemy of agriculture, to impoverish
and, over thousands of square miles, to destroy our farms. The
Mississippi alone carries yearly to the sea more than 400,000,000 tons
of the richest soil within its drainage basin. If this soil is worth a
dollar a ton, it is probable that the total loss of fertility from
soil-wash to the farmers and forest-owners of the United States is not
far from a billion dollars a year. Our streams, in spite of the millions
of dollars spent upon them, are less navigable now than they were fifty
years ago, and the soil lost by erosion from the farms and the
deforested mountain sides, is the chief reason.
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