FORESTS AND RIVERS.* 



At the recent meeting of the International Navigation Congress 

 at Milan, one of the questions taken into consideration was "the 

 influence which the destruction of forests and the desiccation of 

 marshes has upon the regime and discharge of rivers," and seven 

 papers bearing on the subject were read and discussed. Of these, 

 three were from Austria, and the others from Germany, France, 

 and Russia. The problem as to the effect of forests on the water 

 supply of rivers and on climate is of great social importance on 

 account of the agricuUural and commercial interests which are so 

 closely connected with the use of timber, and with the utilisation 

 of running water. 



It is allowed by all the authors of these papers that, due to the 

 improvident way in which the forests have been dealt with, there 

 has been a marked change in the water supply of the neighbour- 

 ing rivers ; that where forests have been cut down brooks have 

 disappeared, and many small rivers that at one time were useful 

 as sources of power are so no longer for want of water ; that in 

 the larger rivers torrents have become more impetuous, and flood- 

 ing more frequent ; while, on the other hand, navigation suffers at 

 times for want of water. 



The greatest harm has been done in the mountain districts, 

 where the steep slopes allow the rain-water to run off" too rapidly, 

 carrying away the surface soil and transporting pebbles and boul- 

 ders into the rivers, causing shoals, thus decreasing their capacity 

 to discharge the flood water. 



The extent to which forests, both on the Continent and in 

 America, are being cut down and destroyed, and large areas of 

 land, which at one time were covered with primaeval forest, have 

 become barren wastes by fire or the lumberman's axe without any 

 attempt at re-afforestation, was one of the subjects dealt with in 

 the presidential address of Mr. J. C. Hawkshaw at the Institution 

 of Civil Engineers in 1902. Mr. Hawkshaw pointed out that, 

 notwithstanding the displacement of wood in building structures 

 by iron, yet large quantities of timber are still required, not only 

 for building purposes, but for temporary structures, such as coffer 

 dams and scaffolding ; pit props for mining ; sleepers required for 

 the railways, which, in this country, he estimated at an annual 

 value of 18 million pounds, and those required for renewals at 

 three-quarters of a million pounds ; while for the railway service 

 of the united States there are required 15 millions of acres of forest 

 land to maintain a supply of sleepers. 



The question for consideration at the Congress was whether the 

 wholesale destruction of forest land for cultivation or for timber 

 supply is having any material effect on the rainfall and consequent 

 water supply ; and the effect of forest destruction on the rivers of 

 the country from which the trees are removed was also considered. 



* From " Nature." Februari) 1, 1906, 



