In this, the year of the elephant, we take a look at the most iconic of African species and its impact upon one particular species of tree, in our special part of the South Luangwa National Park in Zambia.
Elephants are Mother Nature’s processors of nutrients and many species of flora and fauna will suffer, if not disappear entirely, with the demise of the elephant. Many say that elephants are a destructive species and that they destroy their own environments, but one needs to look further than a shredded mopane forest or toppled umbrella thorn to discover the truth behind these acts. Just as a farmer needs to manage his crops, Mother Nature needs to manage her grasslands, her swamps and her forests.
Colophospermum mopane, the mopane tree, is an aggressive tree species that creates mono-cultures, single species dominant areas that exclude most other species. Mopane leaves are high in tannins and when shed by the tree prior to winter, lie in a thick bronze carpet covering the ground. These leaves are favoured as a browse by some animals, but most decompose and contribute to the high mineral content of the thin layer of predominately alkaline soil, over poorly drained soils.
Its botanical name can be broken down to mean `seed produces gum’ which is very accurate, as the winged seeds do produce a resin (which is flammable), that transports the seed by adhering it to animals hooves and coats. And most of the seeds germinate, evident when the new growth emerges in a mopane forest and the ground is carpeted with mopane seedlings. But because the established `cathedral’ trees are usually so dominant, most do not reach the sapling stage, as they soon die off under their canopy or are browsed by kudu, elephant, buffalo and others.
The damage to the mopane forests in the South Luangwa that the herds of elephant wrought in the nineties, was brought on by a prolonged drought. The leaves and bark of the mopane are rich in tannins and therefore do not normally form a substantial part of an elephant’s diet. But the large numbers of elephants were left with little or no browsing nor grazing and the mopane, being a prolific producer of foliage even in dry years, attracted the attentions of the then large numbers of elephants.
The aggressive feeding took an irreparable toll on some areas of the forests, with many of the cathedral mopane left stripped of their bark and others uprooted and left to die. Without the cover of the canopy and with little to no undergrowth to shield it, the thin topsoils were stripped away by the heavy rains that followed the droughts. Once the layer of vegetation protecting this sand is removed, the top soil does not last long, leaving vast areas of sodic soils vulnerable to the effects of erosion, especially if on a slope.
Where the mopane forests did not cover sloping land, many of the seeds that had lain dormant under the canopy now sprouted and a new dominant form of vegetation was established: scrub mopane. This, over time will develop into mopane forest with its dominant cathedral trees, and this particular cycle managed by the elephant will be complete.