GOLD COAST REPORT ON FORESTS. 103 



ruore or less iinpimity, as the soil is quickly re-clothed with 

 luxuriant vegetation, and the chief danger to he guarded against 

 is that of erosion of the hill-sides. 



Such regions enjoy a heavy annual rainfall of 80 inches and 

 more, and the dry season is not only of short duration but is 

 interrupted at pretty frequent intervals by showers of rain attend- 

 ing the tornadoes. The case is very different, however, in those 

 portions of the hinterland, and also sometimes on the sea coast 

 itself, where the rainfall is deficient or where a long and pro- 

 nounced dry reason follows the annual monsoons. It is difficult 

 to state exactly what the minimum annual rainfall determining 

 the " safety '" margin of such a climate is, as so much depends 

 on the distribution of the rain during the various months of the 

 year; but so far my experience leads me to the conclusion that 

 in a climate where the annual rainfall is 60 inches and less the 

 wholesale destruction of the forests is followed not so much by a 

 marked deficiency in the rainfall, as by a general drying up of 

 what were once perennial streams and a gradual transformation 

 of the type of vegetation clothing the locality. 



This change in the vegetation will be realized if the influence 

 of moisture in the soil and the degree of humidity of the air on 

 plant life is recalled. Both these sources of moisture are affected 

 very adversely (for plant growth) by the extensive destruction of 

 forests, with the result that the original forests are gradually 

 replaced by others of a drier type. The transformation is most 

 rapid when extensive areas covered by drier vegetation happen 

 to be situated within a reasonable distance, say a dozen miles or 

 so, of the locality in which the forests (of a moister type) are being 

 destroyed, as there is always a marked tendency on the part of 

 the former to encroach on the habitat of the latter. Once an 

 area becomes clothed with drier vegetation, then the conditions 

 so far as moisture is concerned rapidly change for the worse. 

 Forest fires make their appearance and all the effects on plant 

 life become accentuated. Such alterations in the supply of 

 moisture lead to the transformations of the moist evergreen 

 tropical forests (" rain forests " of Schimper) to the mixed 

 deciduous ones (" monsoon forests " of Schimper, in which a 

 large proportion of the plants shed their leaves during the dry 

 season and replace them at the commencement of the monsoons 

 or wet period of the year), and, if the reduction is continued, the 

 conversion of the latter into the open savannahs so characteristic 

 of the hinterlands of our West African Colonies and also of 

 certain areas along the sea coast where the monsoons are deficient. 

 As a general rule the appearance of the grasses in any large 

 numbers within a forest region otherwise occupied by evergreen 

 vegetation is an almost certain index, in tropical West Africa, 

 of the commencement of such changes. Erosion of the hill-sides 

 and the tendency for violent floods to take place are also greater 

 on land covered with the more open and drier types of vege- 

 tation. As examples of such transformations I may mention the 

 tract of country between Accra and Aburi, w T here the xerophilous 

 scrub gradually gives place to thorn forests and these to the 

 savannahs at the foot of the Aburi hills and these in their turn 



