It is not surprising that the largest terrestrial animals can make a tremendous impact on their habitats through their feeding activities. Imagine an elephant clan moving through a wooded savanna at an ecological density of 10 animals per square kilometer, each individual having a fresh forage requirement of up to 10% of its body weight each day. With an average individual weight of 1,800 kg, this elephant clan would consume 1,800 kg of vegetation each day from each square kilometer of habitat. Another 1,200 kg of vegetation would be wasted in the process. A 200-strong elephant clan would thus remove 60 tonnes of vegetation each day or 21,900 tonnes each year over a 20 km landscape. Even if such a high elephant density is seasonal and unlikely to be sustained over the year, an average density only a third the seasonal figure would still remove a considerable biomass of woody vegetation over large landscapes.
Now, if most of the forage removed by elephants were to be grass or other herbs, there probably would not be much concern. After all, there seems to be no shortage of grass in the African savannas for elephants and other herbivores. Elephants, however, also feed on shrubs and trees, breaking branches, stripping bark, and uprooting huge trees. When a centuries-old stately baobab is reduced to pulp by elephants trying to get at its succulent pith or a fever tree (a major attraction for tourists, who wish to see lions under its shade or a leopard perched on a branch) is pushed over by a bull elephant for just one trunkful of leaves, there is justified cause for concern. It can be argued that the loss of a local clump of trees, attractive to tourists, is not sufficient cause from an objective biological perspective to label the elephant as a destructive creature. When trees begin to disappear over hundreds of square kilometers and the landscape resembles a battlefield with flattened trees, the stage is set for scientific curiosity over elephant-vegetation dynamics to give way to a political war over elephant management.
The "elephant problem," as it was commonly labeled in Africa, dominated the debate over management of the species in the continent during the 1970s. One school of thought considered such drastic impact on vegetation by the elephants as unnatural. The reasoning was that compression of elephants into protected areas or insular habitats by expanding human settlements resulted in artificially high elephant densities and damage to vegetation. A contrary view was that elephant utilization of woody vegetation was merely natural foraging and that "damage" to trees was part of the natural ecology of semiarid habitats. Much has been written about this issue in the African context and less on the Asian situation. My intentions are to review briefly the nature and extent of vegetation change in elephant habitats, consider the role of elephants and other agents of habitat change, and discuss various theories and models of elephant-vegetation dynamics, especially as to their implications for the management of elephants.
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