78 FOREST LANDS FOR THE PROTECTION OF WATERSHEDS. 



forests upon evaporation through the medium of their leaves finds its counter- 

 part in the similar action of the growing crops that overspread deforested areas. 

 As already pointed out, the forests of the mountains increase the evaporation 

 from snow very materially. 



Where the balance lies among all these conflicting influences affecting precipi- 

 tation and evaporation it is impossible to say, and when the records are ex- 

 amined it must be admitted that they afford no answer. So far as the re- 

 searches of science have yet determined, the presence or absence of forests cuts 

 no figure in climatic conditions. These depend upon causes of far greater magni- 

 tude and are influenced, if at all, only to an insignificant degree by the operations 

 of those who occupy the planet. 



The fourth proposition of the forestry argument is that forests are necessary 

 to prevent erosion on steep slopes and the consequent silting of reservoirs and 

 watercourses below. Here again there is the same deficiency of evidence to 

 support the theory that has characterized the three propositions already con- 

 sidered. The author has been unable to find anything to confirm it. In his 

 observations, embracing pretty nearly all varieties of timber laud in the northern 

 two-thirds of the United States, he has still to see a single example where the 

 mere cutting off of forest trees leads to an extensive erosion of the soil. Almost 

 invariably, and it may be said always except in very unusual conditions, a soil 

 that will sustain a heavy forest growth will immediately put forth, wjien the 

 forest is cut down (or even burned down), a new growth, generally in part 

 different from the first, but forming an equally effective cover to the soil. The 

 only approach to an exception to this rule that he has observed is in some of 

 the high mountain forests where the soil is extremely thin and weak and the 

 action of nature in producing vegetable growth is slow. In the forest areas of 

 the East, the growth that follows tree cutting consising not only of new trees, 

 but of briars and small brush of every description accumulates very rapidly 

 and forms a more effective mat against erosion than the original forest itself 

 and equally effective in storing water. Such low growths have also a better 

 effect upon snow melting, because they give both wind and sun freer play. 

 Certainly the ground in a forest under culture, with the debris raked up, is 

 more easily eroded than that of a slashing or second-growth area, or even good 

 meadow or pasture. A forest soil unprotected by forest debris is almost as 

 erosible as a field under culture. 



The increased erosion of the soil, of which so much is heard, does not result 

 from forest cutting, but from cultivation, using that term in its broad sense 

 to include all of man's operations for the occupancy and utilization of the 

 ground from which the forests have been removed. It is the " breaking of the 

 soil " that leads to its erosion by the elements. Roads and trails are one of 

 the great sources of erosion in hilly countries, but plowing and tilling are the 

 principal causes. The question is not one of forests in the first instance, but 

 of how far the cultivation and occupancy of the soil can be dispensed with. 

 Even on steep mountain slopes, where erosion and ruin have resulted, the 

 effect is often due to the clumsy and injudicious work of the husbandman who 

 uses no judgment of cause and effect in the way he exposes the soil to the force 

 of the storms. The successful cultivation of hillsides in every quarter of the 

 globe is an everlasting refutation of the argument that forests are necessary to 

 protect the face of the earth wherever cultivation is practicable. Some classes 

 of cultivated vegetation, like the well-knit turf of meadow or pasture, are a 

 better protection against erosion thau any ordinary forest cover. That there 

 are sections of the country where erosion of the soil is much more rapid than 

 in others under similar conditions is perfectly true. This is especially the case 

 with certain districts in the Southern States, and very likely forest protection 

 is there better than any other; but it is still true that the problem of control 

 of soil erosion on cleared lauds is essentially a problem in cultivation. It is 

 not so much the absence of the forest as it is the cutting of roads and ditches, 

 the upturning of the soil, and the various kindred operations of man that 

 quicken the run-off and increase the surface soil wash. 



The oft-repeated assertion that, owing to the cutting off of forests, our rivers 

 are shoaling up more than formerly may be challenged absolutely. There is 

 nothing in our river history to support it except in a few instances, like the 

 Yuba Kiver in California, where extensive hydraulic or similar operations have 

 produced vast changes. It is exceedingly doubtful if it can be established by 

 any evidence worthy of the name that the streams of the Mississippi basin are 

 more obstructed by sand bars than formerly. The author's observation of 



