MODIFICATION' OF SOmi AFRICAN RAINFAFJ.. 325 



conversion comes the conversiiui of the veld ami the spread of 

 Karroo conditions. Not only ha^ the threat iiitiTior l)asin of 

 South Africa been converted into a semi-desert. ])ut the boun- 

 daries of the Karroo are constanth' increasing. 



Mr. E. R. Bradheld. one of the oldest hydrolosj^ical observers 

 in South Africa, records an area of some 800 acres in the 

 Stormbers: area of the Cape Pro\ince which was, not so many 

 years ago, most valuable agricultural ground, now completelv 

 gutted by erosion and the grass veld practically converted to 

 Karroo. The same gentleman makes mention of another feature 

 of desiccation in the formation of sand-dimes in the neighbour- 

 hood of ]\Iolteno. These dunes now cover some 700 morgen 

 of ground, and new dunes are forming in what less than fifty 

 years ago was heavily grassed land. This is merely the first 

 step of semi-desert conditions to that area. 



Everything, then, tends to i)r()\e the modification of South 

 Africa's rainfall. .\nd as a result o\ this luodification there 

 rises before us a vision of the aftermath to the ijrosperity of 

 the coimtry in the future — some glimpse of what this aftermath 

 must materialise as is afforded by the desiccation of most of the 

 older civilised countries of the world. We look to Arabia, to 

 the Mediterranean countries of Africa, and to Mexico, all in 

 their day renowned for their productiveness, and what do we 

 see? The l(^ss in everv direction of the very power of produc- 

 tion. The need of irrigation, and of more and more irrigation, 

 in a country once intersected in all directions by perennial rivers, 

 once without fear of drought or without need of artificial water- 

 ing, is the best answer to that question. 



Since, then, through human agency, the rainfall of South 

 Africa has been so modified as to threaten the whole future of 

 the country, we, the people of South Africa to-day, have to ask 

 ourselves if we can reverse the process, and cause both an in- 

 crease to take place in the qitantity of moisture precipitated and 

 the manner of precipitation to change, so that, instead of thunder- 

 storms and torrential downpours, we may have more and more 

 soaking showers and mists. The influence of the numerous 

 wattle plantations on the rainfall of Natal prove that even in 

 the course of a few years we can influence the rainfall. I do not 

 mean tc^ extol the wattle as an ideal tree for hydrological pur- 

 po.ses : I do not consider it as such, but at the present time it 

 is the only actual exami)le we have in this country. The ways 

 in which we can influence the rainfall are, firstly, by artificial 

 afforestation, especially of the luountain areas, and by the strict 

 conservation of our indigenous forests ; and, secondly, by cooling 

 til* ground surface of the grass velds. These two means again 

 interact on one another, and must, to some extent, be taken in 

 conjunction. 



Afforestalion. — Tree-planting for commercial i)in-])oses, has 

 been going on in South Africa for the last thirty or forty years. 

 A great deal has been done by the Forest Department, but un- 



