By Duncan Odour

Species consists of individual organisms which are very similar in appearance, anatomy, physiology and genetics having relatively recent common ancestors. Many species survive in specialized habitats. When these habitats are destroyed or fragmented the threat of extinction looms.

Herd of Cape Buffalo in Soysambu Conservancy

Keystone species is defined as one that has a critical role in determining and maintaining the overall relationship of plants and animals within an ecosystem. If a keystone species is removed or declines, the nature of the ecosystem will change dramatically. Keystone species of plants or animals appear to exhibit a particularly large influence on the ecosystem they inhabit. Keystone Species are essential to ecosystems and biodiversity.

Zebras are keystone species in Soysambu conservancy.

Elephants as a keystone species.

As keystone species, elephants stop the progression of grassland to forest or thicket by weeding out the trees and shrubs.   Elephants browse on these woody plants, yanking young trees out by their roots or stunting their growth by eating the growth points on their branches or kill it slowly by prying away its bark. Without elephants the grasslands overgrow with woody plants and convert to forests or to shrub-lands. This conversion begins when woody plants, particularly various species of acacias e.g (Acacia nilotica, xanthophloea) sprout among the grasses. Left unchecked, these sprouts can grow and reproduce, eventually forming a closed stand of trees or shrubs. Once in place, the stand’s interlocking branches and leaves shade out the grasses. Without enough sunlight to survive, the grasses dwindle, the grassland disappears. When grasses disappear, so do grazing antelopes and without antelopes, the packs and clans of carnivores also disappear. The newly growing forest supports a new web of life that is more impoverished and less productive feeding fewer species than the grassland.

An elephant grazing does not harm the grasses as grasses are adapted to live in harmony with their grazers sacrificing a few leaves in exchange for keeping their roots and growth points intact.
Grasses ensure this compromise by forming leaves that connect to their roots through weak and narrow bases which snap when a grazer eats the leaves leaving the roots safely below the ground. When a keystone species disappears from its habitat, that habitat changes dramatically. The keystone’s disappearance triggers the loss of other resident species, and the intricate connections among the remaining residents begin to unravel.
As resident species vanish, other species move in or become more abundant. The altered mix of species changes the habitat’s appearance and character.The “new” habitat looks different from the original one, housing a new mix of plants and animals. Often, the new habitat supports fewer species and works less efficiently than the original one as nutrients and energy turn over more slowly and less efficiently, biological diversity dwindles and the landscape begins to change.