Eye in the Sky: Dr. Adam Cruise
A trophic cascade is an ecological process which starts at the top of the food-chain and cascades all the way down to the bottom.
African elephants, for example operate, in the natural landscape in this way. Biologists often refer to African elephants as ecosystem ‘architects’ and ‘gardeners’. They break branches off trees, sometimes the entire tree itself, that then creates microhabitats for seedlings and small vertebrates, like dwarf mongooses and invertebrate animals like butterflies. Elephant dung is a food source for dung beetles and a variety of birds like the spurfowl and quails, which in turn nourish the soil and provide a seed dispersal mechanism for many tree and plant species. Other bird species such as the ground hornbill and the pearl-spotted owlet rely on elephants to create nesting sites in hollows of the old dead trees knocked over by them.
The Keystone Role of Elephants in Ecosystem Maintenance and Biodiversity
In the dry months, elephants dig holes in the dry riverbeds to access water, which is then available to all other water-dependent species. Their large size creates pathways through the
thickets for other smaller species like impala to follow and even for humans when hiking through the African bush. Through their feeding habits they make browse available for other
browsers, they maintain structure in savannahs by reducing the tree to grass ratio and create
nutrient rich microclimates underneath dead trees. This means grazers such as buffalo need elephants to ensure they have enough grazing fodder.
The African elephant is also an ‘umbrella species’ in that it requires large areas of suitable habitat to maintain viable populations that support an array of associated species. Elephants have vast ranges and require large intact areas to maintain their populations. By creating such vast areas in which we protect elephants, we ultimately protect many other species that share their habitat with elephants.
Impact of Fencing and Resource Manipulation on South African Ecosystems
However, in South Africa, the high level of fencing, especially in the many smaller private reserves, as well as natural resource manipulation, such as the provisioning of perennial artificial water supplies (which are evident even in the largest of the national parks), impacts negatively on the movement patterns and consequently on the intensity of the wild habitat used by elephants. This leads directly to wilderness degradation. Wild habitat degradation in small fenced reserves, in conjunction with severe droughts, negatively affects elephants and all other animals in the area. Within South Africa, there are only two elephant subpopulations that can move naturally as fences restrict movements elsewhere.
And, it is not only the charismatic megafauna that should be viewed in this trophic cascading light. Dung beetles are as important as elephants in dispersing and breaking down the tons of dung dropped by all animals, not just elephants. The great forests and savannahs of Africa are fertilised by legions of dung beetles rolling, dispersing and burying dung. The rolling also scatters the seeds necessary for growth and rejuvenation of vegetation. Take the lowly dung beetle out of the ecosystem and we will likely see the whole system collapse.
The Essential Role of Elephants in Shaping Ecosystems
Back to elephants. There is a lot of contention about elephants destroying the natural habitat. However, the presence of an elephant knocking over a tree hides the fact that the fallen tree will shape and create a new world in time, not just for the future of elephants, but for all the grazers, browsers, insectivores and seed-planters whose futures depend on the fact the tree was knocked over.
Through the process of time, a being is inextricably intertwined with its surroundings and vice versa. The long-term invisible temporal movements of the elephant, the dung beetle and all the other interconnected species that rely on each other are critical for the survival of the wild environment as a whole, just as the intricate and dynamic interrelations that make up the wild environment nourishes and gives life to these animals over time.
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