A functional hypothesis of the threat of local extirpation of woody plant species by elephant in Africa

Species vulnerable to extirpation by elephant are those: whose attributes predispose adults to pollarding, uprooting or ringbarking; adults coppice poorly, hence mortality occurs; mortality is not compensated by regeneration and recruitment owing to the impact of elephant and other agents; species have a restricted distribution; and poor dispersal ability constrains recolonisation. Threat of their local extirpation has increased because of an increased probability of encounter with elephant attributed to artificial boundaries that have constrained movement, and proliferation of water points that has reduced spatial refuges for plants and weakened density-dependent regulation of elephant populations. Degradation of grasslands, wetlands and riparian areas has forced elephant to subsist on woody vegetation for a longer period of the annual cycle. A reduction in water points should increase local elephant density and attendant density-dependent effects of increased foraging distance, nutritional stress, calf and juvenile mortality, and predation, and reduce reproduction. Eliminating human predation after 4000 years in some parks has contributed to the problem. Mitigation of the threat of local extirpation should concentrate on configuration of boundaries, water provision, simulated predation, minimum reserve size, and not pursue non-definable notions of elephant carrying capacity.