By Sarah Savory:
I use this example to teach children Holistic Decision Making and Ecological Literacy – it was never a case of there being too many kudu but a case of human management resulting in an imbalance of predator and prey which was causing too many kudu to behave unnaturally – without enough pack hunting predators to keep the kudu herds bunched together and constantly on the move, they began to spread out and stay too long which resulted in the knock-on consequence of over browsing of the trees and the devastating longer term consequence of humans blaming the damage on too many kudu and either culling or translocating them. The exact same thing happened with elephants – we took the humans out of National Parks but that was an apex predator keeping hundreds of thousands of elephants behaving naturally. As soon as people were removed, the elephants stopped moving naturally and the ecosystem damage began to get worse.
All of these reductionist human management decisions results in ecosystem imbalance – there is a vital symbiotic relationship between grass plants, and the correct balance of herbivores and pack hunting predators.
So, overgrazing causes desertification of grasslands but so does over resting.
When we rest land in non-brittle (humid) environments it will recover, but resting land in brittle (arid) climates leads to desertification. This is because the micro-organisms that break down plant material are activated by moisture, so in humid areas, micro-organisms are constantly breaking down vegetation, but in brittle environments during the long, dry seasons, something else is needed to provide the moisture that activates micro-organisms to begin breaking down old vegetation. These brittle environments are the world’s grasslands and make up about two-thirds of the planet’s land mass. They rely on a symbiotic relationship between plants, herding animals and predators to survive.
Imagine all the different shapes and sizes of hooves and feet of the herding animals here in Africa, and how different they are. They have each been perfectly designed by nature to impact soil: from impala’s sharp little hooves, ideal for breaking up the soil surface and trampling down small plants, with their delicate mouths designed to nibble softer grasses…through every size and shape of feet, hooves, mouths and dung, until you get to elephants who eat courser grasses as their big, flat feet trample vegetation to help cover and protect the soil, while aerating and fertilising it. While this is all going on, many trillions of microorganisms are being activated by moisture in the animals’ guts, dung and urine to begin breaking down plant material.
Timing is vital: when herds stay too long, plants get over-grazed. If herds don’t bunch together or don’t stay long enough, the soil doesn’t get mulched. The timing is perfected by predators, whose job is to keep herds bunched together and moving, always flowing with the unpredictable variables going on around them, ensuring the health and survival of all.