Slide 22: Test 3: + elephants
Adding elephants into the system, however, throws things completely out of kilter. Since elephants are known to prefer browsing (although they can survive as grazers as well), their impact on the tree population is considerable. The proportion of grass grows very rapidly, and both tree basal area and tree height drop to a low stable (coppiced point), as the elephants push over the larger trees and coppice the smaller ones. This stable, highly productive coppiced tree population is optimal for supporting elephants, since the level of production is so much higher than fully-grown trees.
The elephant population climbs rapidly from an initially moderate level to a very high one (in excess of 4t/km2). Even more importantly, the browsing pressure from elephants would push the browser population into competitive collapse before 2040, and then a shift in diet to include more graze would cause the coarse grazer population to crash within the next 25 years. The main reason for this is that there are no real predators for elephants, and the question that follows is why has this effect not been observed in nature? It seems the most probable reason is that there is no such thing as an undisturbed wild population, as hypothesized. For tens of thousand of years, the top predator in the African savanna has been the human, and in fact the hunter of our ancestors is the only reason we are not knee-deep in elephants today.