nd the decimation of indigenous fauna. This phase gained effective momentum during approximately the middle of the nineteenth century and continued well into the first quarter of the twentieth century. The destruction of valuable, productive and soil protective plants occurred largely during this phase.
The thinning of palatable vegetation (Phase One) under grazing by stock (primarily sheep) took place at a rate which could not be compensated for soon enough by less palatable and grazing resistant species. There was thus a considerable time lag (Phase Two) before the replacing species could build up sufficient momentum to offset the results of thinning out.
The result of this lag was that for many decades the general vegetation was very much sparser than it used to be or than could potentially be supported by the existing climate and soils. This phase lasted up to approximately the nineteen-sixties, gaining its peak from the nineteen-twenties well into the nineteen-fourties and early nineteen-fifties. This phase was characterised, as a result of the sparser vegetation, by increased run-off and high rates of erosion with an accompanying decrease in rainfall effectivity. This alarming phase spawned theories and investigations into droughts, climatic change and desert encroachment. During this Second Phase the greatest reduction in grazing capacity of the veld, as well as in stock numbers took place - especially during the late nineteen-thirties. The widespread development of bare patches (kaalkolle) was a conspicuous result of this phase. The development of these bare areas reached a maximum during the 'thirties and 'fourties.
During the whole of the Second Phase the Third Phase had begun its development with greatly varying and variable pace.
During this phase the replacement of the thinned-out. vegetation of the Second Phase had gained momentum. The replacing species were largely those not normally eaten by stock and those variously called invaders, unpalatable and undesirable species, encroaching species (large and small) and Karoo pioneers. Some of these species were ecologically so successful that they had, to a considerable extent, blurred the development of the second phase in many localities as for example in the Karoo mountains.
Under continuous and severe grazing stress the development of Phase Three can be inhibited.
A direct result of the Phase Three development was the near complete obliteration of bare patches in the Karoo Region (especially during the late nineteen-sixties and nineteen-seventies), and the general thickening-up of the vegetal cover. Vast areas were occupied and dominated by less desirable and less productive problem plant communities and species. This replacement has already reached such proportions that a relative state of stability exists. The position is now such that the general vegetal cover is nearly as dense, as, and, in some instances, is even denser than that of the vegetation in Phase One due to a more effective water economy.
The present situation is significant in three respects: namely, that it provides an excellent opportunity for the redevelopment of Phase One vegetation; that erosion and run-off has slowed down; and that loss of grazing capacity has occurred generally.
Inevitably, especially during Phase Two, considerable loss in the potential of soils to support the original vegetation had taken place. It is therefore at present quite impossible, even under ideal treatment, to revert to a Phase One type of vegetation. However, there undoubtedly exists in Phase Three a vast potential and a reclamation slack which should be exploited to the full in order to approach the Phase One situation as nearly as possible.
It should also be realized, that over the last two centuries many ecological processes have been disrupted, diverted and deflected, whereas others have gained unprecedented momentum and even in some instances, stability. To change such vast and stimulated ecological processes and such stabilized situations requires concerted and co-ordinated efforts especially in the sc