Sperrgebiet – Un-forbidden territory? Not quite yetJuly 15, 2012
The Benguela Current – A vital link in the global oceanic chainJuly 15, 2012
By Hu Berry
Scarce and susceptible, some of the Namib’s succulents have become rare because of the ‘collector’ or plant thief who unscrupulously removes them from their natural habitat to replant or sell them to willing buyers.
It is a lucrative, but illegal and dishonest trade that results in truckloads of succulents being transported illegally to neighbouring countries and overseas.
The elephant’s trunk or ‘halfmens’ (Afrikaans for half-person), Pachypodium namaquanum, stands sentinel in the southern Namib.
According to legend, a group of Nama forefathers were fleeing across the Gariep River from an enemy tribe, struggling to evade capture or death. The gods mercifully changed them into sedentary half-human plants, where they remain with their heads turned northwards toward their pursuers.
This romantic and illusionary state is rudely interrupted when ruthless collectors rip the elephant’s trunk by the roots from its rocky resting place and sell it overseas for as much as U$1 000 per plant.
The crown of leaves on the stem, resembling a hairy human head, enhances the impression of a person impersonating a plant. The explanation for this bizarre orientation is that these plants grow on shaded slopes, leaning northwards to ensure that their leaves and developing flowerheads, produced during the cool, foggy winter months, are maximally exposed to the rays of the sun.
Going by the impressive scientific description of Mesembryanthemum guerichianum, the ice plant is easily recognised by its permanently ‘wet’ appearance due to the fleshy leaf surface being covered in look-alike water droplets.
Its successful survival strategies ensure that it ranges from the South African Karoo through Namibia to Angola. This species belongs to the so-called ‘leaf succulents’, which are prolific in the southern, winter-rainfall area of the Namib. Indeed the Family Mesembryanthemaceae contributes 37% to the endemic flora.
The term ‘biodiversity hotspot’ does not refer to temperature (which can reach 45ºC), but to the abundance of unusual succulent plants. This globally important ‘hotspot’ boasts no less than 70 species per 10 square metres. The plants thrive in the desiccated landscape of Namibia’s Succulent Karoo, where an uncommon quartz gravel ecosystem supports high levels of plant endemism and diversity. About 1 840 succulent species survive here by storing water in swollen leaves, stems and roots.
Add the terms ‘cremnophytes’ (cliff-dwelling plants) and ‘chasmophytes’ (crevice-dwelling plants) to the list of succulents and it becomes clear why new species are still being discovered. Cliffs and crevices in rock faces are mostly highly inaccessible. Sheer cliff faces are botanically among the most poorly explored of all terrestrial habitats on earth.
If ‘half-people’ and ‘ice plants’ conjure up visions of ghostly settings, consider the addition of the most virulent succulent, indeed the most noxious plant in Namibia. Euphorbia virosa juts its formidable candelabra of vicious spines skywards, visually asserting that its milky sap will blind a human and destroy sensitive tissue if ingested. Early San people accorded this lethal latex the respect it deserves by adding it to the concoction they daubed onto their arrow tips. In contrast, the butter tree, Cyphostemma currorii, bears its yellowish, papery bark and unmistakable barrel-shaped stem benevolently on rocky screes. Its relationship, albeit distant, to the table grape, is verified by its kinship with the succulent wild grape, Cissus nymphaeifolia, which occupies the rugged escarpment of the Kaokoveld.
Proof that the San have provided modern man with their intimate knowledge of wild plants is borne out by the commercial exploitation of Hoodia currorii, which belongs to the wild oleander family. The sap of this succulent is thought to serve as a natural appetite suppressant. Slimmer ladies may soon attest to its efficacy, without resorting to the side effects of other synthetic slimming diets. The Namib hoodia also has further medicinal value in that it lowers blood pressure and provides relief from colds and indigestion. However, its flesh-coloured flowers smell attractive only to flies and other pollinating insects that like the odour of carrion.
If the San recognised the value of certain succulents, then the ancient Greeks introduced bitter Aloe vera to medicine. No fewer than 26 aloe species rear their rosette, succulent leaves, topped by tubular inflorescences, adding an array of splendour to Namibia’s landscapes. Many have penetrated the vastness of the Namib Desert, such as the well-known quiver tree, Aloe dichotoma, the common name referring to the San’s use of its hollowed-out stems as containers for their poison arrows.
If you are a fat, juicy desert plant, the chances are high that you’ll be eaten. An ingenious way to avoid this is to look like a stone. So closely do Lithops (meaning stone-like) plants resemble pebbles that avid collectors dub them ‘stone plants’. Lying low beneath the surface with hardly any stem present, some species expose only the upper surface of their bulbous, fused leaves to capture sunlight. This translucent window to the world is all they need to exist out of sight to hungry animals and unlawful collectors. To reproduce and release their seeds, these hidden marvels require raindrops on their fragile surface. Desert showers trigger a response and eject the dry, minuscule seed capsules to ride on the raindrops and find a new place to germinate between the stones.
This article appeared in the 2009/10 edition of Conservation and the Environment in Namibia.
Hu Berry was a scientist, conservationist and specialist tour guide. He was one of Venture Publications' most valued authors. Sadly he passed away in July 2011. To read more about him click here.