1 40 SCIENCE IN AFRICA 



the character of natural vegetation were noticeable as early as 

 1 751, within one hundred years of the first settlements, and that 

 these changes can only be attributed to the effects of overgrazing. 

 Indeed there are many examples of erosion in southern and eastern 

 Africa which have resulted from European methods of farming. 



Once the causes are recognized and the best ways of preventing 

 erosion are discovered, it is comparatively easy to arrest the trouble 

 on land under management by white peoples. A much greater 

 problem is to be faced in the vast areas farmed by Africans, whose 

 methods can be controlled only with extreme difficulty by Euro- 

 pean administrative officers and agriculturalists. 



The collection of data in the field, showing the severity and ex- 

 tent of damage to the soil in each territory, is urgently needed. 

 Such surveys of soil erosion are being made in parts of Africa, and 

 the subject was discussed at the second conference of East African 

 soil chemists in 1934 (East Africa, Conference, 1935), when a paper 

 by Mr. Gethin Jones outlined the results of a reconnaissance survey 

 of the extent of soil erosion in Kenya. In Uganda also, a special 

 survey has been made for the Teso district and a wider survey of 

 the protectorate is also being conducted. It is to be hoped that 

 further studies of this type will be organized. 



The question of soil erosion is closely allied to that of the regu- 

 lation of water-supplies. It is generally admitted that the destruc- 

 tion of natural vegetation, forest or otherwise, adversely affects 

 the water-supply, causing floods in times of heavy rain and the 

 disappearance of springs and streams in the dry season, while the 

 maintenance of the natural vegetation prevents run-off and causes 

 rain water to percolate into the soil and issue subsequently in the 

 form of springs. One of the most complete investigations into this 

 question has been carried out in the northern part of Tanganyika by 

 Teale and Gillman (1935), as mentioned in Chapter III. The 

 conserving power of forest reserves in suitably chosen areas is now 

 widely recognized, and action is being taken with regard to their 

 creation or enlargement in many parts of the continent; these 

 questions are discussed in Chapter VII. Agricultural methods of 

 soil conservation are considered in Chapters XIII and XIV where 

 the subjects of cultivation and animal husbandry are discussed in 

 some detail in relation to soil deterioration and erosion. 



