GOLD COAST REPORT ON FORESTS. 105 



insignificant ill regions where the rainfall is heavy and the 

 climate huinid practically throughout the year. 



As far as vegetable growth is concerned a climate with a well- 

 marked dry season is, so to speak, in a condition of unstable 

 equilibrium; the slightest variations in the soil then become of 

 great importance to plant life, and it is in such regions, of which 

 the hinterlands of our West African Colonies are the most im- 

 portant examples for the purpose of this report, that the question 

 of forest conservancy becomes one of grave concern. Destroy 

 the forests found there along the banks of streams, on the higher 

 hills, and in sheltered hollows, and the country will rapidly get 

 drier though the rainfall may remain practically the same as 

 before the damage was done'. The soil becomes no longer 

 capable of retaining the moisture precipitated on it once the 

 forests are removed. 



As regards the influence of forests on rainfall, reliable statistics 

 extending over a long period are not available for tropical 

 countries. In Europe it has been shown that forests do, but only 

 to a very small extent, increase the annual precipitation of rain. 



Quite recently, however, Mr. A. Walter, Chief Assistant of 

 the Royal Alfred Observatory, Mauritius, has made a thorough 

 examination of the data available with a view to investigating 

 the effect, if any, that the wholesale destruction of the forests 

 on the island has had on its climate. He " finds in the smoothed 

 rainfall curves extending over the period 1860 to 1907 evidence 

 that the cutting of the forests may have had some little effect on 

 the total fall, but has had more effect on the number of rainy 

 days. The distribution through the year is almost more im- 

 portant than the amount. The rainy days in the districts 

 denuded of forests have been decreased lay about 30 days per 

 year, but under such conditions that the amount due to these 

 30 days is only about 6 to 10 inches, whereas the annual varia- 

 tion of total rainfall is often 60 inches." (See page 610 of Vol. 

 78 of " Nature," where a brief extract of Mr. Walter's investi- 

 gations is given.) 



This inquiry has, of course, been confined to a limited region 

 (705 square miles) having an insular climate. There is every 

 reason to believe that ihe influence of forests is much more pro- 

 nounced in the case of continental areas in the tropics, where the 

 differences between the various seasons of the year are very 

 marked. A reduction by one month of the number of rainy 

 days in the year would, if established in such a climate, have 

 very important effects on the vegetation of the locality. 



The action of forests as wind-breaks is too obvious to call for 

 further remarks ; their use as barriers against the spread of 

 fungoid and insect attacks from one series of plantations to 

 another has of late been 'better recognized and adopted in tropical 

 countries. Mixed forests of the type usually found there are 

 amongst the most effective agencies that can be employed for 

 such a purpose. Any tropical country that is mainly dependent 

 on agricultural pursuits for its development cannot afford to 

 ignore this beneficial action of forest belts. 



