124 THE FUTURE OF ARID LANDS 
shows a measure of correlation with the eleven-year sunspot 
cycle (g). In this region also within the past forty years or more 
the levels of certain lakes have shown a progressive fall, and ice 
caps have shrunk, indicating a climatic change. Wayland believes 
that the Kalahari climate is slowly reverting to a more arid 
phase, but at the same time he says, “It 1s unthinkable that the 
change will be an entirely one-way process; moreover, these 
climatic mergings take time—geological time” (28). 
In southern Africa an increasing aridity since European occupa- 
tion began is generally admitted, although opinions still differ as 
to the extent to which this is due to climatic change or to man’s 
interference with vegetation and other natural conditions. 
Bosazza et al. (2) expressed the view that the desert encroachment 
of South Africa is the result of the activities of man and his com- 
panion animals, although others have seen in meteorological 
records and in the altered regime of rivers evidence of late climatic 
change. 
Gevers (13), for example, described drying rivers in the north- 
eastern Transvaal. He recorded that Dr. Schumann, Chief 
Government Meteorologist, in 1934 showed that there had been 
a noticeable decrease in rainfall over great parts of the Union 
since the eighteen nineties, and he quoted figures showing a 
steadily declining rainfall from 1906-07 to 1946-47 at the Duivel- 
skloof and Ravenshill stations, in the vicinity of the rivers de- 
scribed. He stated that there was no question of the widespread 
desiccation in the area referred to, and that there was also little 
doubt that the marked decrease in rainfall since 1926 was the 
predominant cause. There is equally little doubt that the effects 
of the incidence of rainfall have been greatly modified by man- 
made agencies, such as despoliation of the vegetal cover (forests, 
bush, scrub, and grasslands) with consequent removal of long- 
conditioned absorptive topsoil and increase in runoff. It is quite 
clear by comparison with former conditions and ocular evidence 
of the present day that all streams not rising in protected or com- 
paratively well preserved catchment areas have lost their staying 
and recuperative powers and that many of them have been 
turned into stormwater drains. Gevers considered also that the 
