early times it was unnecessary for him to return to the piece of forest he had previously 

 cut down. In later times he returned but only after the lapse of a century or more when 

 a forest of second growth species had grown up. It was the increase in population and 

 the disappearance of so much forest which resulted in the shortening of this period of 

 return. 



In British West Africa this method of cultivation is termed farming and the system 

 is more fixed, since the people are under the rule of numbers of Chiefs, each having a 

 fixed area of country with fixed villages under his jurisdiction. In British and French 

 West Africa between the sea and the southern Sahara and including East Africa and the 

 Sudan, this method of cultivation is in force over great areas of the so-called bush or 

 savannah where the forest, for it is still forest though much degraded, is considered 

 still to be good if it has a height of 30-40 feet and a corresponding density. The ser- 

 ious trouble is that the populations have greatly increased and with them the grazing 

 and pasturing herds. But the area of land under a Chief and his people remains a con- 

 stant. This results in a shortening of the fallow period and with a consequent more 

 open and shorter scrub growth which produces less ash at the burning and a poorer crop. 

 But more serious, an interference with the water supplies commences to make itself 

 felt. This may be summarised as follows ;- 



(a) In the past the population of the regions now deserts, or on the way to become 

 deserts, was very small. The slow depreciation of the soil conditions caused 

 by a wasteful utilisation took many centuries to make its appearance. As is 

 known, the nomadic tribes moved away from an area becoming unproductive to 

 return to it, perhaps many years later, when it had recuperated. It was the ear- 

 liest form of 'crop rotation' or more correctly 'grazing rotation'. 



(b) With the increase in populations and in consequence in the intensity of the mis- 

 use of the soil the migration from an exhausted area was not followed, on any 

 scale by a return at a later date. For those later migrations of more numerous 

 populations were not apparently undertaken till the water supplies had become 

 so unreliable and the soils so poor that neither the one nor the other were capa- 

 ble of supporting them. 



(c) The decrease in rainfall supplies in springs, streams, rivers and wells precedes 

 the decrease in the rainfall. Here apparently lies one of the greatest stumbling 

 blocks to an appreciation in Africa of what is taking place under the misuse of 

 the soils in the upsetting of the balance of nature. The rainfall becomes unre- 

 liable or intermittent. 



(d) In the past this stage probably continued through the lapse of many centuries. 

 The fluctuations waxed and waned over long periods. Later generations took 

 the fitful rainfall as something which had now become a climatic reality which 

 had to be put up with. Generations of people lived and died under these con- 

 ditions as they are doing today. Travellers studying the land and its people, 

 being misled by this fitfulness or intermittancy, reported that in parts the rain- 

 fall was improving and with this improvement the ground was becoming re- 



124 



