SOME PROBLEMS OF RESEARCH 9 



cult to prove, that forests slow up the run-off of waters, thereby 

 making streams run perennially instead of intermittently, and con- 

 sequently their destruction, especially on watersheds and high 

 ground, means that water is available in the soil for shorter periods. 

 It is generally assumed also that a single stand of trees, such as a 

 cocoa plantation, is less effective than the natural mixed forest in 

 holding up the run-off. In the forest belt of West Africa there are 

 many cases of destruction for the purposes of establishing planta- 

 tions which have led to a very great reduction of forests during the 

 past twenty-five years. In the Gold Coast, for example, it has been 

 estimated that, if the recent rate of cutting were to go on unchecked, 

 there would be no closed forest left in another fifty years. The forest 

 question is so involved with meteorological conditions, that the 

 number of balancing factors is legion. Some people hold that 

 forest actually increases the rainfall directly, others that its destruc- 

 tion causes rain to be precipitated in occasional heavy storms rather 

 than in frequent gentle falls. Again, in certain areas the destruc- 

 tion of forest in one place may affect the climate of another region 

 far removed; for example, in the Guinea lands, where the rainfall 

 of the dry regions bordering the Sahara is dependent on the local 

 monsoon from the Atlantic Ocean, which passes over the belt of 

 high forest, it is supposed by some that destruction of the high 

 forest will cause a reduction of rainfall in the dry regions of the 

 north. 



Opposed to these changes, most of which lead to lessened water- 

 supply, forestry departments are attempting to maintain the original 

 environment by the reservation of forest areas, and in some cases 

 by direct planting. Here again, another question arises in that 

 many exotic trees which are used in afforestation grow more 

 rapidly and have a higher transpiration rate than the original 

 indigenous trees. Accordingly it is supposed that the new forests, 

 in parts of South Africa for example, actually reduce rather than 

 increase the soil moisture. The amount of timber available for 

 building and firewood clearly depends upon the area of forests, 

 and the conditions imposed upon its use. It is a striking fact that 

 at present there are practically no data as to the amount of timber 

 required by native populations. 



Wild animals are important factors in the environment, as food, 



