58 rRESiJ)i:xTiAL address — section c. 



and tlie other downward — are tlie natural sequence of events 

 begun with man's actions, either toward protection or toward 

 destruction. 



In the case of forest destruction the change is even 

 greater, for if we look on good forest as the highest climax 

 type, and remove that forest or reduce its canopj^ Avithout due 

 care as to the rapid recovery or renewal of that canopy, it 

 promptly becomes, through man's agency, either rough grass 

 land or more or less unstable mixed vegetation which is liable 

 to pass into erosion before it ever g^ets settled into grass-veld, 

 though the latter is its natural tendency if left alone, prior to 

 the next step upward in the succession, which in forest con- 

 ditions would be forest, if the opportunity were given. But 

 when the down-grade is once begun, man's action harrlh' ever 

 helps recovery, but much more frequently helps to change the 

 position from bad to worse, till eventually a suitable forest 

 slope is Avashed to the bare rock, and can no longer maintain 

 any vegetation. 



Dr. I. Croumbie Brown uttered this warning very strongly 

 in his many writings over fifty years ago, but the public still 

 ignores the plain fact, and farmers farming stock on what is 

 naturally forest land sincerely believe they are doiug the right 

 thing, or following the only possible course, in burning for 

 immediate returns, irrespective of the ultimate result. 



Climatic Changes. 



Let us now look at the result of this destruction of vegeta- 

 tion upon the climate. Where the process involves the change 

 of a dense canopy and hum\is, whether of forest or of grass, 

 with its soil-protection and moisture absorption, into a bare 

 surface from which the run-off is immediate and intense, or 

 into any of the succeeding lower stages in which the run-off 

 and erosion are even worse, the atmosphere naturally loses 

 all the moisture, which then goes to form the ri^'er flood, or 

 even the river's regular flow, all of which water, when retained 

 by the humus of the undamaged surface, eventually finds its 

 way into the atmosphere and falls again as rain, sometimes 

 time after time. 



We can onlj' regard the flood-water and also much of the 

 ordinary river flow as so much water wasted, except in so tar as 

 it is used for irrigation or household or power purposes, and we 

 can only regard what sinks into the subsoil, or is transpired 

 or evaporated, as so much water saved for further use. In 

 other words, the less flow to the river indicates the greater 

 saving of water by natural means for further and immediate 

 use inland. I am aware that this is contrary to a common 

 idea that eucalypts, wattles and other trees of rapid growth 

 dry the country, and that this is shown in the reduction of 

 the off-flow. J^o such drying happens, however, but, on the 

 contrary, wherever the off'-flow is reduced that much water 

 is saved from flowing away and is passed into the atmosphere, 

 ready to fall again. It does sometimes happen that these trees 

 tax their sites heavily, which indicates that these particular 

 sites are not well suited for such trees. But wherever the 



