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514 LIFE
Generally speaking, it may be stated that forests, which in this respect
may be compared to the sea, diminish the natural differences of temperature between the various seasons, while their destruction exposes a country to all thje extremes both of cold and heat, and adds still greater violence to the atmospheric currents. If we are to put faith in certain authors, the mistral itself, the terrible wind which swoops down upon the
Cevennes and brings desolation into Provence, has been a scourge of mankind, and has blown in its full violence only since the disappearance of
the forests on the adjacent mountains. In the same way marsh-fevers
and other endemic diseases have often broken out in a district after the
woods, or even mere sheltering screens of trees, have fallen under the axe.*
As to the general flow of the surface waters and the climatic conditions
which depend upon them, there is no room to doubt that the result of the
clearing away of forests is a disturbance of the regularity of the above-
named conditions. The rain, which by the intersected branches of the
trees, descends drop by drop, and subsequently trickles slowly through
the dead leaves and the net-work of roots, when the forests are destroyed,
flows down fast upon the ground and forms temporary rivulets; instead
of descending by subterranean sources to the lower strata and springing
up again in fertilizing springs, it runs off rapidly on the surface of the
ground, and is lost in the streams and rivers. Up-stream the ground is
dried up, and down-stream the body of running water is so increased, that
floods are converted into inundations, devastating the whole country
along the river-side; dreadful disasters are thus brought about, similar to
those which were caused by the Loire and the Rhone in 1856.
But man is now able to take account ofthe influence which his agency
has exercised upon climate, either by improving it or making it worse;
and any mischief that he has done he is able to undo. He knows that by
again planting woods he has the power of modifying the extremes of temperature, and of equalizing the amount of rain; he knows that by devel
* oping a system of irrigation he is able to increase the fall of moisture, as
has been proved by the observations made in Lombardy during the last
century ;f lastly, he can make a district healthy by draining the marshes,
by clearing the surface of the land from decaying matter, and by modifying the various kinds of cultivation. This was the case in Tuscany, where
the valley of the Chiana, once almost uninhabitable, into which the swallow scarcely dared to venture, has been completely set free from the
marsh-miasmas by the rectification of an irregular slope, covered with
pools and lagoons. In the same way, the marshes of the district which
was the ancient Etruria have become much less dangerous to the health
ofthe inhabitants since the Tuscan engineers filled up the low grounds on
the sea-shore, and have taken care to prevent the mixture of salt and fresh
water which took place at the -mouth of the streams. The amelioration
of the air to be breathed is the mode by which man will resolve the important question of acclimitization ; for the only hot countries that are
* George P. Marsh, Man and Nature. - f Ibid.
| Title | The ocean, atmosphere, and life |
| Creator | Reclus, Elisée |
| Publisher | Harper |
| Place of Publication | New York |
| Date | 1873 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000571 |
| Type | Books/Pamphlets |
| Transcript | 514 LIFE Generally speaking, it may be stated that forests, which in this respect may be compared to the sea, diminish the natural differences of temperature between the various seasons, while their destruction exposes a country to all thje extremes both of cold and heat, and adds still greater violence to the atmospheric currents. If we are to put faith in certain authors, the mistral itself, the terrible wind which swoops down upon the Cevennes and brings desolation into Provence, has been a scourge of mankind, and has blown in its full violence only since the disappearance of the forests on the adjacent mountains. In the same way marsh-fevers and other endemic diseases have often broken out in a district after the woods, or even mere sheltering screens of trees, have fallen under the axe.* As to the general flow of the surface waters and the climatic conditions which depend upon them, there is no room to doubt that the result of the clearing away of forests is a disturbance of the regularity of the above- named conditions. The rain, which by the intersected branches of the trees, descends drop by drop, and subsequently trickles slowly through the dead leaves and the net-work of roots, when the forests are destroyed, flows down fast upon the ground and forms temporary rivulets; instead of descending by subterranean sources to the lower strata and springing up again in fertilizing springs, it runs off rapidly on the surface of the ground, and is lost in the streams and rivers. Up-stream the ground is dried up, and down-stream the body of running water is so increased, that floods are converted into inundations, devastating the whole country along the river-side; dreadful disasters are thus brought about, similar to those which were caused by the Loire and the Rhone in 1856. But man is now able to take account ofthe influence which his agency has exercised upon climate, either by improving it or making it worse; and any mischief that he has done he is able to undo. He knows that by again planting woods he has the power of modifying the extremes of temperature, and of equalizing the amount of rain; he knows that by devel * oping a system of irrigation he is able to increase the fall of moisture, as has been proved by the observations made in Lombardy during the last century ;f lastly, he can make a district healthy by draining the marshes, by clearing the surface of the land from decaying matter, and by modifying the various kinds of cultivation. This was the case in Tuscany, where the valley of the Chiana, once almost uninhabitable, into which the swallow scarcely dared to venture, has been completely set free from the marsh-miasmas by the rectification of an irregular slope, covered with pools and lagoons. In the same way, the marshes of the district which was the ancient Etruria have become much less dangerous to the health ofthe inhabitants since the Tuscan engineers filled up the low grounds on the sea-shore, and have taken care to prevent the mixture of salt and fresh water which took place at the -mouth of the streams. The amelioration of the air to be breathed is the mode by which man will resolve the important question of acclimitization ; for the only hot countries that are * George P. Marsh, Man and Nature. - f Ibid. |
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