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The Drakensberg Mountains of South Africa and Lesotho In January 2002, Hilary and John Birks visited the Drakensberg Mountains
in KwaZulu-Natal, South Africa and in Lesotho (Maloti Mountains)
as part of an
Alpine Garden Society Expedition led by David McDonald and John Grimshaw. Introduction The Drakensberg Mountains (28°30' – 31°20'S, 27°00' – 29°40'E)
form a 300-km border between the landlocked mountain kingdom of
Lesotho (formerly Basutoland; = Mountain Kingdom) and South Africa.
The Drakensberg Mountains are also known as the Barrier of Spears or 'a row of spears point upwards'. The Zulu name (Quathlamba or uKhahlamba) refers to the jagged spires of the Drakensbergs. The Drakensberg Mountains are the highest part of the 'Great Escarpment' in southern Africa rising to over 3000 m. The highest peak (Thaban Ntlenyma, 3482 m) is the highest mountain in Africa south of Kilimanjaro in Tanzania. The 'Great Escarpment' lies parallel to the south-east coast of South Africa and runs from the Eastern Cape into Zimbabwe. It separates southern Africa from the Interior Highveld Plateau, and its formation was initiated during the break-up of Gondwanaland. The area was called Drakensberg ('Dragon Mountain') by the early Dutch settlers (Voortrekkers) because of its resemblance to the ridges of a dragon's back. The steep ridges of its dragon-like back are formed by headwater erosion of rivers that separate the Highveld Plateau from the coastal lowlands of southern Africa.
Environment Geology, Topography, and Soils Much of the Drakensberg area lies on the high plateau above 3000 m of Lesotho bounded by the Drakensberg escarpment to the east, north, and south extending into South Africa. It is mostly formed of basalt lavas, up to 1400 m thick and forming sheer cliffs up to 460 m thick. These are underlain by the Clarens Sandstone (up to 2500 m), often undercut by caves with many fine bushman paintings. The Drakensbergs are thought to be some of the oldest mountains in the world and are in the centre of a continent rather than at continental edges. With the break-up of Gondwanaland about 200 million years ago, basaltic lavas flowed through fissures and capped the sedimentary sandstone for about 20-50 million years from the early Jurassic to the Cretaceous. Soils are thin on the basalt plateau, are almost non-existent
on the near-vertical escarpment, and are deep on the Clarens Sandstone.
Soil pH is about 5.5-6.0. Soils are very deficient in nitrogen
and phosphorus and have high levels of exchangeable aluminium.
The summit soils become wet and water-logged in the summer and
in the winter they are subject to freezing at night and thawing
during the day. It is not uncommon to find ice-heaved stones, stone
polygons, gelifluction terraces, and frost hummocks ('thurfur')
on the high plateau, features more commonly associated with high-latitude
arctic areas. Climate The main climatic feature is its summer rainfall. The area has a temperate climate but summer rather than winter rainfall as in the Cape floristic area. The mean temperature of the warmest month (January) at 3050 m is about 10.9°C. The mean annual rainfall is 635 mm in the west, increasing to 2000 mm on the high plateau. It decreases as one goes east, due to rain-shadow effects. In the alpine belt (above 2750 m), the climate is severe with a mean annual temperature of 5.7°C. The highest recorded temperature is 31°C (January 1972) and the coldest is -20.4°C (June 1967). For half the year, the minimum temperatures are below 0°C. There is snow-lie for four months or more in protected gullies and on south-facing slopes. Frost occurs daily in the winter, and there are 183 days with frost at 3050 m altitude. Mist is common throughout the year. Strong winds are common at high altitudes, especially in the afternoons and evenings during spring and summer. Heavy, often torrential, thunderstorms are characteristic of the area in the summer
Land-use and fire Fire is the dominant ecological factor in the area, either natural or human-induced fires. Natural fires are often caused by lightning in the spring or summer or by boulders rolling down and colliding with other boulders to produce sparks that ignite dry grass swards. The natural lightning ground-flash density is about 12-14 flashes per km2 per year. Human-related fires have a long history in the area, with Bushmen burning areas to produce new grass-growth that would attract large game for hunting. More recently, Bantu and European farmers have burnt the grasslands to produce winter grazing for sheep and cattle. The alpine areas are burnt by Lesotho people on a fairly regular basis. Summer grazing is by cattle, horses, sheep, and goats and there is extreme (300%) overstocking of grazing animals in Lesotho. This overstocking leads to severe soil erosion and inwashing of silt, especially after torrential storms. Large areas in Lesotho have been flooded as part of the Lesotho Highlands Water Project for South Africa, with a value of about $38 million per year by 2030. Similarly, KwaZulu-Natal Drakensberg produces water worth about $930 million per year for South Africa. Botanical Features At a broad-scale, the Drakensberg lie within the 'grassland' biome of southern Africa and in phytogeographical terms they have affinities with both the Afromontane and Afroalpine phytogeographical regions in Africa.
The vascular plant flora is very rich, with about 2800 species including four endemic genera and about 450 endemic species. The largest families are Compositae, Scrophulariaceae, Gramineae, Leguminosae, Iridaceae, Cyperaceae, Orchidaceae, and Ericaceae. The largest genera are Helichrysum (102 species), Senecio (100) Erica (34), Disa (32), Crassula (30), Delosperma (30), Thesium (30), Eragrostis (25), Hypoxis (24), Lotononis (24), Sebaea (24), Wahlenbergia (22), Cyperus (20), Kniphofia (20), Pelargonium (20), Gladiolus (19), Selago (19), Berkheya (18), and Moraea (18). The Drakensberg flora has been intensively studied by Olive Hilliard and Bill Burtt, both now retired but still very active at the Royal Botanic Garden, Edinburgh. Their major publication (1987) on The Botany of the Southern Natal Drakensberg is an invaluable source of information. The small booklets by Olive Hilliard on Trees and Shrubs, Grasses, Sedges, Restiads and Rushes, and Flowers (orchids, lilies, etc.) are extremely useful field guides. Else Pooley's (2003) Mountain Flowers is a superb and easy-to-use photo-illustrated flora of the Drakensberg and Lesotho. The flora has strong affinities with the Cape Floristic Region as well as the Afromontane Region, and relatively weak links with the Afroalpine Region of East Africa. Eighty-eight genera in Drakensberg have their centres of diversity in the Cape Floristic Region (e.g. Erica, Protea, Helichrysum).
This belt runs from 1280 m to 1830m but the lowest altitude we visited was at 1750 m. The major habitats visited were Podocarpus latifolius forest, Protea savannah, grasslands dominated, surprisingly, by grasses with C4 photosynthesis (possibly a result of repeated burning over thousands of years), and cliffs and rock outcrops in the Royal Natal National Park. Some plants of Podocarpus
latifolius woodland
Subalpine belt This belt (1830-2750 m) consists primarily of Protea savannah (rather rare and largely confined to steep rocky areas), grassland, mires, flushes, and 'sponge' bogs fed by springs emerging along geological boundaries, and cliffs and rock outcrops. Some plants of the subalpine Protea savannah Alpine belt The alpine belt begins arbitrarily at 2750 m and extends to the highest ground at 3482 m. It consists of alpine heath 'tundra', alpine grassland and open summit areas, mires and flushes, aquatic and stream-side communities, and cliffs. Some plants of alpine heath 'tundra', grassland, and open areas The genus Helichrysum The largest genus in the Drakensberg is Helichrysum (Compositae) with 102 species. It is mainly an African genus, with some representation in Mediterranean Europe, south-west Asia, southern India, Sri Lanka, and Australia. There are about 600 species worldwide, and 245 of them occur in South Africa. They are mainly herbs, but some are climbers or low shrubs and they occur in a wide range of habitats, including grassland, woodland, scrub, cliffs, screes, wind-blasted open summit areas, rock outcrops, and mesic areas. They avoid wet areas of mires, flushes, and 'sponge' bogs. Some representative Drakensberg species are shown here. Why is the Drakensberg Flora so Rich? The Drakensberg Mountains are an international 'hot-spot' of plant
biodiversity, not only of vascular plants (over 2200 species in
an area of about 40,000 km2 (about the size of Belgium)) but also
of bryophytes. Unfortunately nothing appears to be known about
the Quaternary vegetation history of the area. The endemic vascular
plants (16% of the flora) are a mixture of palaeo-endemics and
neo-endemics. In the absence of any factual data on vegetational
and environmental history, all we can do is to speculate about
possible contributory factors for the high diversity. The following
factors may have contributed to the extraordinary diversity. Conservation and the Future Only 3% of Lesotho and 97% of KwaZulu-Natal Drakensberg are protected as Nature Reserves, National Parks, or Wilderness Areas. At present many of the alpine areas (mainly in Lesotho) are unprotected. The major threats to the Drakensberg flora are (1) overstocking, excessive grazing, and soil erosion, (2) invasive 'exotic' species, (3) increased conversion of grasslands into areas for arable agriculture in Lesotho, (4) hydroelectric development in Lesotho, and (5) 'global warming'.
The dark areas are the predicted extent of the 'alpine' climate under the regional future scenario of the IPCC for 2100. A major reduction in the 'alpine' climate is predicted, with 'alpine' areas becoming confined to the very highest areas only. The alpine areas would become very fragmented and a major loss of species is predicted. In addition, the climate predictions are for much reduced snow cover, leading to a loss of available water. Such a loss would have major ecological and economic implications for the Drakensberg Mountains and its flora, fauna, and human societies.
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The Mountains cover an area of about 40,000 km2 and the area ranges
from 1800 m to 3482 m (summit of Thabana Ntlenyana - a local Lesotho
name meaning 'beautiful little mountain', Lesotho). The area includes
montane, sub-alpine, and alpine vegetational belts. The alpine
area is the only true alpine region in southern Africa. The Drakensbergs
are one of Southern Africa's eight 'hot-spots' of botanical diversity
in terms of species richness and endemism. They are thus an area
of particular interest to botanists interested in biodiversity
and the causes of richness and endemism.
Three major altitudinal belts are recognised within the Drakensberg
Mountains – the montane belt up to 1830 m characterised by
Podocarpus latifolius forest; the subalpine belt between 1830 and
2750 m characterised by fynbos (= species-rich heath) that has
largely been converted into grassland; and the alpine belt between
2750 and 3482 m characterised by Erica-Helichrysum 'tundra-like'
heath and grasslands. It is debatable if there is 'true' alpine
vegetation in the Drakensberg. The alpine belt is defined climatically
and altitudinally as having its lower boundary between 2750 and
2865 m, rather than being defined floristically or physiognomically.
The alpine belt is part of the Afroalpine phytogeographical region,
whereas the subalpine and montane belts belong to the Afromontane
region. The flora shows gradual change with species disappearing
or appearing with increasing altitude. However, the altitudinal
gradient is interrupted by the Drakensberg escarpment. The extent
of the alpine belt (areas above 2750 m) is shown above.
Montane belt
McDonald et al. (2002) delimited the climate envelopes for 16
alpine species in Drakensberg today to define the modern 'alpine'
climate. The area with such a climate is shown in grey on the map.
