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
In the volume cited in the text, Reclus informs us that "the village and
the great thermal establishment of Bareges in the Pyrenees were
threatened yearly by avalanches which precipitated themselves from a
height of 1,200 metres and at an angle of 35 degrees; so that the
inhabitants had been obliged to leave large spaces between the different
quarters of the town for the free passage of the descending masses.
Attempts have been recently made to prevent those avalanches by means
similar to those employed by the Swiss mountaineers. They cut terraces
three or four yards in width across the mountain slopes and supported
these terraces by a row of iron piles. Wattled fences, with here and
there a wall of stone, shelter the young shoots of trees, which grow up
by degrees under the protection of these defences. Until natural trees
are ready to arrest the snows, these artificial supports take their
place and do their duty very well. The only avalanche which swept down
the slope in the year 1860, when these works were completed, did not
amount to 350 cubic yards, while the masses which fell before this work
was undertaken contained from 75,000 to 80,000 cubic yards."--La Terre,
vol. i., p. 233.]
Minor Uses of the Forest.
Besides the important conservative influences of the forest and its
value as the source of supply of a material indispensable to all the
arts and industries of human life, it renders other services of a less
obvious and less generally recognized character.
Woods often subserve a valuable purpose in preventing the fall of rocks,
by mere mechanical resistance. Trees, as well as herbaceous vegetation,
grow in the Alps upon declivities of surprising steepness of
inclination, and the traveller sees both luxuriant grass and flourishing
woods on slopes at which the soil, in the dry air of lower regions,
would crumble and fall by the weight of its own particles. When loose
rocks lie scattered on the face of these declivities, they are held in
place by the trunks of the trees, and it is very common to observe a
stone that weighs hundreds of pounds, perhaps even tons, resting against
a tree which has stopped its progress just as it was beginning to slide
down to a lower level. When a forest in such a position is cut, these
blocks lose their support, and a single wet season is enough not only to
bare the face of a considerable extent of rock, but to cover with earth
and stone many acres of fertile soil below. [Footnote: See in Kohl,
Alpenreisen, i., 120, an account of the ruin of fields and pastures, and
even of the destruction of a broad belt of forest, by the fall of rocks
in consequence of cutting a few large trees. Cattle are very often
killed in Switzerland by rock-avalanches, and their owners secure
themselves from loss by insurance against this risk as against damage by
fire or hail.]
Public-domain text, read in full here on John Shaqi.
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