402 FOREST DESTRUCTION. 



that was destro3'ed ma,v be slow in returning, even after the forest 

 condition is established, and great length of time, in tens or hundreds 

 of years of useful growth, may be lost; but, in the great majority of 

 cases, the type of forest once best adapted to the land will clothe it 

 again. 



The destruction of a forest through fire or otherwise brings about 

 two results. In the first place, it disturbs the general balance of 

 nature, sets free geological activities which were previously held in 

 check, and begins a long process of readjustment. In the second 

 place, it profoundly modifies the vegetation for a longer or shorter 

 term of years, both before and after the forest condition is restored. 



The chief geological agent set at work by forest destruction is 

 water. We are already well persuaded in general of the effect of 

 forests on the flow of streams. Yet an illustration which I ma}^ bor- 

 row from an unpublished paper by Mr. Filibert Roth will serve to set 

 the matter iii a clear light. If an ordinar}^ desk or table be tilted and 

 water is sprinkled on its surface, the water speedily runs off. If the 

 tilted table is covered with an inch or two of loose soil, the water 

 falling upon it is at first somewhat retarded in its journej^ to the lower 

 edge; but soon not only does it find its wav there with rapidity, but it 

 carries with it relatively large amounts of soil. As yet no reservoir 

 has been established on the sloping surface. If now a layer of cotton 

 batting, which we may liken to the mat of decaying leaves and twigs 

 which constitutes the forest floor, be laid on the surface of the soil 

 erosion ceases, the water which falls sinks gently into the soil, and 

 the soil on the surface of the <able has become in effect a reservoir for 

 the temporary retention of water. Such a reservoir will continue to 

 give out water long after the rain has ceased to fall. 



Over large areas of our country, especiallj' in the far West and in 

 the Southern Appalachians in the East, the water-conserving property 

 of the forest is for the present, and is likely long to continue, its most 

 important one. In addition to the loss of water by promoting its 

 useless waste in floods there is the loss of the soil itself. Fertile soil 

 is the product of long geological processes and is perhaps the most j 

 valuable asset of any nation. Forest destruction tends to convert the 

 soil of productive fields into costly and dangerous bars at the mouths 

 of rivers and harbors, by permitting its transportation In' water to the ■ 

 sea. The washing away of cleared soil is proceeding with astonishing 

 rapidity in many parts of the country. The damage is most visible 

 in the gullying of hillsides, but it is not less destructive in the removal 

 of the surface soil without gullying, where heavy rains and smooth 

 steep slopes make the process possible. Estimates of the loss from i 

 this source have been made, notably by Professor Shaler, of Harvard, 

 but it is sufficient to say here that the damage is on a gigantic scale 

 and that it is .steadily increasing in the United States. 



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