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 scientific fields of plant ecology, and veld utilization and management.
Karoo vegetation has now reached a most critical stage in Phase Three which, if mismanaged, will inevitably develop into a Phase Four situation.
The active spreading and increase in so-called invading species, are positive indications of the progress toward Phase Four in which they could eventually become dominant.
This phase is where Phase Three, with continued development, has arrived at a point where productive and utilizable species have reached such a low level that the less desirable, semi-palatable species and even those considered unpalatable have become the main source of natural fodder. There already exist clear-cut examples of the Phase Four situation over large areas in the western Karoo and mountains. Subjecting Phase Four vegetation to increasing utilization, especially under pressure, would inevitably lead to the destruction of protective vegetation. The general consequences of this would undoubtedly be many times more severe than those encountered in the Phase Two situation. The development of a Phase Four situation should be prevented at all costs.
Phase Four vegetation consists basically of a stable and relatively permanent cover of unpalatable or inedible vegetation dominated by one or two species. The floor (i.e. open ground between the established species) will at time become covered by largely short-lived or annual herbaceous species; these include the lesser grass species which may be annual or bi-annual. The grazing capacity of Phase Four vegetation is on the average low and is subject to considerable fluctuation as it is practically entirely dependent on rain. The phase Four situation is thus an unpalatable shrub (or succulents or woody low trees) matrix filled in by a short-lived floor cover dependent on rain for its development. In this situation run-off and erosion rates are usually high, but not necessarily so. To reclaim Phase Four vegetation would be many times more difficult and would take much longer than that 