ientific 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 of the Phase Three situation. In fact, Phase Four would probably require artificial veld reclamation measures. The destruction of Phase Four vegetation the development of Phase Five appears to be a final stage; this is where vegetation is practically entirely destroyed and the soil completely exposed to erosive agents.
It must be borne in mind that the concept of vegetation change as set out above has bearing on the general situation in the Karoo Region. At any particular locality, depending on its grazing history and climate – especially average rainfall - the various phases may vary in duration and intensity and may overlap and merge considerably or may even be indistinguishable. The various phases should never be considered as distinct or discrete stages.
In the marginal grassveld regions the Phase One situation rapidly develops into Phase Three. Phase Two is usually of relatively short duration and is usually not severe. Also, as a result of the higher potential of grassveld areas there are far greater prospects of the reversal or halting of phases here than in arid areas, excluding possibly that of the western arid grasslands (Bushmangrassveld). It should be pointed out here that there are still vast tracts of veld - especially in the eastern dry grassveld and adjoining grassveld which are in the late stages of Phase One.
The ecological unravelling of these phase changes and those taking place within phases, afford some of the most demanding and complicated studies that can be undertaken by the plant ecological and pasture sciences. The identification of the phases as set out above can afford the basis for developing new philosophies and new approaches to the reclamation of vegetation.
It should be pointed out here that the geographical distribution of insects, birds, mammals and reptiles are also affected by the development of the phases.
In the Karoo Region there are deserts, semi-deserts and arid lands, such as they have been over the centuries. It cannot be disregarded that there is desert encroachment a