National Geographic : 1896 Nov
THE ECONOMIC ASPECTS OF SOIL EROSION turned fields. So long as the earth is covered by the normal forest growth the strong roots are likely to pass through the soil and fix themselves in the crevices of the underlying rocks and clamp, so to speak, the loose materials in their place. In this way it comes about that one of the effects of deforesting a coun try, even where the lesser vegetation is allowed to develop, is to increase the rate at which the soil goes away to the streams. As yet this country has not been long enough exposed to the de structive effects of tillage to afford striking instances of the effect of the reckless war which is waged upon the woods by the sav ages who play that they are the agents of civilization. In Europe examples of the irreparable damage which may thus be wrought abound. Perhaps the most striking are to be found in the Ap enines, near Florence, where it is possible to walk for miles on mountain slopes without setting foot on anything but bare rock fields, which a century or so ago bore heavy forests nurtured in a fertile, if not deep, soil. The last of the Medicis who held these woods as crown lands cut the timber without any provision for the replacement of the trees, with the result that the fine soil, before it had time to obtain protection from plants, was swept away. In this manner a great area has been doomed to age long sterility and a region made desolate which might with proper management have continued to be helpful to man for an unlimited period. The mountainous countries of the Old World, with their vast reaches of bare rock slopes, which down to recent centuries were forest-clad, show the destructive effects of man's heedless assault on the earth. In this country there has not been time for this process of destruction by the axman to manifest itself in a very serious way, yet in the Appalachians we can see the evil in rapid progress. South of Pennsylvania there is, according to my reckoning, based on observations in every state in that upland country, an aggregate area of not less than three thousand square miles where the soil has been destroyed by the complete removal of the woods and the consequent passage of the earthy matter to the lowlands and to the sea. At the rate at which this process is now going on, the loss in arable or forestable land may safely be reckoned at not less than one hundred square miles per annum ; in other words, we are each year losing to the uses of man, through unnecessary destruction, a productive capacity which may be estimated as sufficient to sustain a population of a thousand people.