76 FOREST LANDS FOB THE PROTECTION OF WATERSHEDS. 



In the record-breaking flood of 1907 in the Sacramento Valley 88 per cent of 

 the normal for the month of March (based on twenty-one years' observation) 

 fell in three days (17-19), and on one day the precipitation ranged from 5 to 

 8 inches at the different stations. 



In the extraordinary flood of May and June, 1908, in western Montana, the 

 precipitation for May," at four selected stations, was 6.5 inches and for June 

 4.2 inches. The greater portion of this fell late in May and early in June. 

 The normal for May is 2.6 inches and for June 2.3 inches. 



Similar conditions prevail in every great flood, and the true explanation is 

 found in them and not at all in the presence or absence of forests on the water- 

 sheds. Whether the forests are in any way responsible for the precipitation 

 itself and so, indirectly, for the floods, brings up the third of the foregoing 

 general propositions, viz, that forests do increase precipitation. However 

 strong may be the popular belief in this theory, there is nothing in the records 

 of rainfall to give it substantial support. The author has had occasion, in 

 connection with his official work, to compare the rainfall records in the north- 

 ern half of the United States from the Atlantic to the Pacific, often with this 

 particular point in mind, and he has never found anything to indicate a change. 

 So far as he has examined European records the same result holds, and he 

 believes it to be true the world over, except where climatic changes have re- 

 sulted from causes entirely disconnected with the operations of man in chang- 

 ing the face of nature. In fact, the claim that forests increase precipitation 

 (about 10 per cent, according to Mr. Pinchot), leads to some contradictory 

 results in the forestry argument. Coincident with our recent high waters, 

 which are attributed so largely to deforestation, there has been an increase in 

 precipitation, where there should, apparently, have been a decrease. It is 

 evident that where one rule applies the other fails. So, likewise, it is held 

 that forests are necessary to protect mountain slopes because of the greater 

 precipitation prevailing there; yet the forests are said to increase this precipi- 

 tation materially. 



There is really very little, theoretically, to support the claim that forests 

 insure precipitation. It is said that the cooler status of forest arens condenses 

 moisture and induces precipitation ; but if tliis were so in midsummer, when 

 the least precpitation falls, how about the rest of the year when no such dif- 

 ference exists, but the reverse, if anything? Take, for example, the great for- 

 ests around the source of the Yellowstone. During the period when the bulk 

 of the precipitation falls the temperature of the forests can not differ materially 

 from the outside, and it is impossible to believe that the forest exercises much 

 influence upon the snowfall. 



The fact that these high areas are generally wooded is frequently cited to 

 prove that forests produce the higher rates of precipitation which also prevail 

 there. Rut would it not be more reasonable to say that the forests flourish 

 there because of the higher precipitation, and that the latter is due to the ele- 

 vated situation and consequent lower temperature? Is not this, in fact, the rea- 

 son why precipitation is nearly always greater upon the hills than upon the 

 neighboring lowland? The mountains are nature's wine press by which she 

 extracts from an unwilling atmosphere the elixir of life for the hillsides and 

 the valleys below, and she does this whether the forests have been cut away 

 or not. 



In one respect, and a very important one, forests diminish precipitation, and 

 that is in the deposition of dew. Dew is essentially an open-country phenomenon, 

 where the radiation of heat from the earth's surface is unobstructed. Clouds 

 or high cover of any kind, and also wind, interfere with this process and prevent 

 the dew from gathering. It collects in full strength on low -shrubbery, to a less 

 degree on small trees, as in orchards, and penetrates for short distances under 

 forest cover. In the heart of the native forest of full-grown timber, however, 



As a step in the crescendo of gloomy forebodings upon this subject, that 

 have filled the periodicals during the past twelve months, the following from 

 the September Scrap Book is the very latest : " When our forests are gone the 

 streams will dry up, the rivers will cease to run, the rain will fall no more, and 

 America will be a desert." Considering how large a percentage of our forests 

 has already disappeared, the extraordinary rains in all parts of the United 

 States during the past year are not exactly in line with this dismal prophecy. 

 If one were to judge from the records of the past few years only, he must 

 conclude that deforestation is increasing rainfall. 



