FORESTS IN RELATION TO CLIMATE AND RAINFALL. 137 



in all its details, but the main issues may be shortly mentioned. 

 They are : — 



Forest in relation to CUmate and Rainfall, 



The Regulation of Moisture. 



Forest Produce required by the Country. 



1. Forests in Relation to Climate and Rainfall. 



This relation is of a very peculiar nature. On the one hand, a 

 covering of forest vegetation reduces the temperature of the air 

 and soil, increases the relative humidity and tends to increase 

 precipitation. On the other hand, the exceptionally high 

 temperature prevailing in spring and early summer over the 

 centre of the peninsula is one of the agencies which bring about 

 the summer monsoon rains. Thus afiorestation might produce 

 local precipitations, but it might also weaken the force of the 

 south-west monsoon, or delay its arrival. Moreover, investiga- 

 tions instituted of late years by the Government of India, have 

 shown that the effect of forests on the rainfall is so small, at any 

 rate in the low lands, that it can be neglected ; it could not 

 compensate for any interference which extensive afforestation 

 might exercise upon the arrival of the south-west monsoon. As 

 a matter of fact, three-fourths of the areas here under considera- 

 tion is utilized for cultivation and grazing grounds. The south- 

 west monsoon must, therefore, remain the main source of moisture 

 in India. On the whole, the climate and rainfall of India are 

 subject to influences compared with which the effect of a limited 

 area of forests must always be very small. At the same time, the 

 shade of forests and of trees generally will be gratefully accepted 

 in a country as hot as India. 



2. The Regulation of Moisture. 



The regulation and husbanding of moisture in a country with 

 an uncertain rainfall like India is of great importance as regards 

 evaporation of moisture and the mechanical action of water. 



The difference in evaporation between a forest-clad area and 

 one exposed to the full effect of the sun and air currents is much 

 greater in a tropical climate than it has been proved to be in a 

 temperate climate. Hence, the presence of forest acts highly 

 beneficial wherever the rainfall is limited, or unfavourably distri- 



