ABSTRACT
The main impact of man on ecosystems can be summarised in one word, simplification. This process has come about for a number of reasons:
Removal of competitive species; usually confined to larger mammals and dominant plants (trees). Competition can be in the form of:
competition for food resources, and/or
competition for living space.
Clearance of an area to make way for agriculture.
Removal of species which are antagonistic towards man; e.g. pests, weeds, carriers of disease.
Involuntary processes which bring about additional simplification as a result of conditions 1–3.
Deliberate removal of a dominant species can alter the meso- and micro-habitat conditions such that dependent subordinate species can no longer survive the changed circumstances. Allen (1980) has suggested that for every deliberate removal of a major species, the survival of as many as 30 minor species may be thrown into jeopardy.