The Earth as Modified by Human ActionMarsh, George P. (George Perkins)
History
The Earth as Modified by Human Action
Marsh, George P. (George Perkins)
Conservation of natural resources; Human geography; Nature -- Effect of human beings on; Physical geography
Charnock's experiments in two years show an absorption of from seventeen
to twenty-seven per cent.] Besides, even admitting that the water from
summer rains is so completely evaporated as to contribute nothing
directly to the supply of springs, it at least tends indirectly to
maintain their flow, because it saturates in part the atmosphere, and at
the same time it prevents the heat of the sun from drying the earth to
still greater depths, and bringing within the reach of evaporation the
moisture of strata which ordinarily do not feel the effects of solar
irradiation.
Influence of the Forest on the Flow of Springs.
It is an almost universal and, I believe, well-founded opinion, that the
protection afforded by the forest against the escape of moisture from
its soil by superficial flow and evaporation insures the permanence and
regularity of natural springs, not only within the limits of the wood,
but at some distance beyond its borders, and thus contributes to the
supply of an element essential to both vegetable and animal life. As the
forests are destroyed, the springs which flowed from the woods, and,
consequently, the greater water-courses fed by them, diminish both in
number and in volume. This fact is so familiar throughout the American
States and the British Provinces, that there are few old residents of
the interior of those districts who are not able to testify to its truth
as a matter of personal observation. My own recollection suggests to me
many instances of this sort, and I remember one case where a small
mountain spring, which disappeared soon after the clearing of the ground
where it rose, was recovered about twenty years ago, by simply allowing
the bushes and young trees to grow up on a rocky knoll, not more than
half an acre in extent, immediately above the spring. The ground was
hardly shaded before the water reappeared, and it has ever since
continued to flow without interruption. The hills in the Atlantic States
formerly abounded in springs and brooks, but in many parts of these
States which were cleared a generation or two ago, the hill-pastures now
suffer severely from drought, and in dry seasons furnish to cattle
neither grass nor water.
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