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
It was a narrow view of geography which confined that science to
delineation of terrestrial surface and outline, and to description of
the relative position and magnitude of land and water. In its improved
form it embraces not only the globe itself and the atmosphere which
bathes it, but the living things which vegetate or move upon it, the
varied influences they exert upon each other, the reciprocal action and
reaction between them and the earth they inhabit. Even if the end of
geographical studies were only to obtain a knowledge of the external
forms of the mineral and fluid masses which constitute the globe, it
would still be necessary to take into account the element of life; for
every plant, every animal, is a geographical agency, man a destructive,
vegetables, and in some cases even wild beasts, restorative powers. The
rushing waters sweep down earth from the uplands; in the first moment of
repose, vegetation seeks to reestablish itself on the bared surface,
and, by the slow deposit of its decaying products, to raise again the
soil which the torrent lhad lowered. So important an element of
reconstruction in this, that it has been seriously questioned whether,
upon the whole, vegetation does not contribute as much to elevate, as
the waters to depress, the level of the surface.
Whenever man has transported a plant from its native habitat to a new
soil, he has introduced a new geographical force to act upon it, and
this generally at the expense of some indigenous growth which the
foreign vegetable has supplanted. The new and the old plants are rarely
the equivalents of each other, and the substitution of an exotic for a
native tree, shrub, or grass, increases or diminishes the relative
importance of the vegetable element in thegeography of the country to
which it is removed. Further, man sows that he may reap. The products of
agricultural industry are not suffered to rot upon the ground, and thus
raise it by an annual stratum of new mould. They are gathered,
transported to greater or less distances, and after they have served
their uses in human economy, they enter, on the final decomposition of
their elements, into new combinations, and are only in smnall proportion
returned to the soil on which they grew. The roots of the grasses, and
of many other cultivated plants, however, usually remain and decay in
the earth, and contribute to raise its surface, though certainly not in
the same degree as the forest.
Public-domain text, read in full here on John Shaqi.
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