I go SCIENCE IN AFRICA 



of forestry to native agriculture, and measures taken to ensure the 

 interests of forest conservation that it is worth discussing the Vv^ork 

 done in the different territories in detail, with particular reference 

 to the British territories under the control of the Colonial Office. 



In Northern Rhodesia native systems of agriculture vary consider- 

 ably, but all are dependent in part on the clearing and cultivation 

 of bush. In the north-west and north-east the natives depend almost 

 entirely on the temporary cultivation of forest land. The ecological 

 survey officers, Trapnell and Clothier (1937), who have correlated 

 native systems of agriculture with forest types, conclude that the 

 extent of a given agricultural system could be defined by the 

 vegetation type or group of types characterizing the region used. 

 The time required for soil and forest recuperation between periods 

 of cultivation is so long that the area of forest available in some of 

 the reserves is inadequate for the population. Colonel Gore Brown 

 has pointed out,^ for instance, that in Mpika district each house- 

 hold requires about ten acres of land every two years, and the 

 same land cannot be used again for twenty-five years. Therefore 

 the optimum population is one household per 125 acres of suitable 

 forest, but the actual density is far in excess of this. In addition to 

 the inroads of cultivation in the forests, the growing mining industry 

 is beginning to make itself felt, so that reservation of the savannah 

 forest, for which steps have only recently been taken, is urgently 

 needed. 



In Nyasaland mnch. of the savannah forest has been modified by 

 shifting cultivation and fire, and in places destroyed, with resultant 

 soil erosion. This process has been accelerated to a considerable 

 extent by the traditional mode of cultivation of finger millet 

 [Eleusine coracana\ which makes extravagant demands on the land, 

 as described by the Conservator of Forests, Mr. Clements (1933). 

 Wood or grass is burnt by natives to heat the soil before planting 

 this crop, which peculiarly responds to partial sterilization. In 

 some regions, where the forests were destroyed long ago, regrowth 

 is cut on a rotation of two to ^v^ years for this purpose, and many 

 acres of regrowth are used for burning one acre of garden. Under 

 this system a new garden is required after one or two crops, and soil 

 impoverishment, followed by crusting, desiccation, and erosion, is 



* Private communication. 



