St Helena

The endemic of St Helena

by Irina Russell

"Fragments from the wreck of an ancient world"

St Helena is a tiny island, 17 km by 10 km, in the South Atlantic Ocean north­ west of Cape Town at a latitude 150 56'S and longitude 50 42'W. As there is no air­ port, the usual way of getting there is on the RMS St Helena, which does the round trip from Cape Town (some 2 700 km away) several times a year. The island was discovered on 21 May 1502, the feast day of St Helena, by the Portuguese explorer Joao da Nova Castella. In his journal, he wrote of the island's fair air and water. This 'fairness' could also be applied to the contrasting beauty of its emerald hills, grassy pastures and wind-eroded desert, with multicoloured valleys and ridges, as well as to the hospitality of its people. St Helena is a volcanic island that rose above the Atlantic over fourteen million years ago. It has a complex topography of ridges and deep gorges, plains and hills, and its main feature is a high central ridge surrounded by radiating valleys. The highest point on the island is Diana's Peak (820 m above sea level). Its near neigh­ bour, Mount Actaeon, is only slightly lower. The geographical position of St Helena and the timing of its emergence have given rise to an endemic flora and fauna of exceptional taxonomic isolation and scientific interest. Their ancestors colonized St Helena from prehistoric forests that have long disappeared from the world's continents - hence the description by Hooker, over a century ago, of the plants of St Helena as 'fragments from the wreck of an ancient world'. The island lies well within the tropics but the climate is modified by its mid-ocean position, the consistent southeaster and the cooling influence of the Benguela cur­ rent. Generally, it is warm, damp and equable, although there is incredible varia­ tion in the weather within the limited area of the island itself. The average rainfall TOP: Lot, a spectacular volcanic pipe (phonolite intrusion) dominates Sandy Bay. varies from 381 mm between 0-305 m above sea level to 965 mm above 610 m. On average, fog or mist is recorded on about 130 days in the year. A Boer prisoner of ABOVE: St Helena ebony was war provided one of the more amusing descriptions of St Helena's climate: 'There common in the Sandy Bay area in the Seventeenth Century. are two seasons; (1) the rainy season, in which rain is the rule and sunshine the Photos: Irina Russell. exception; (2) the dry season, which resembles the rainy one so much that the mis­ taking of one for the other has never yet been ascribed to ignorance'. Unfortunately, St Helena has a legacy of ecological destruction typical of oceanic islands and today, most of the endemic seek refuge in the dense tree fern thicket covering the highest peaks. After its discovery, goats and pigs were estab­ lished there for victualling purposes, while human settlement began in 1659. This

138 September 2005 Veld&Flora led to the almost total destruction in the 1700s of the woodland of endem­ ic cabbage trees on the lower slopes around the tree fern thicket. Lemons were introduced in 1718 and thrived at first, but later pests and diseases became established and uncontrollable (partly because there are so few natu­ ral predators on the island). Although the names Lemon Grove, Lemon Valley and Lemon Tree Gut all appear on the large-scale map, there are now no lemon trees to be found. William John Burchell, who lived on St Helena from 1805 to 1810 as schoolmaster and act­ ing botanist, introduced plants from all parts of the world, but was oblivious to the danger they posed to the endemic species. Species of Cinchona introduced from South America in the 1860s were even planted on Diana's Peak in an attempt to establish a quinine industry. In 1907, the islanders were rescued from semi-starvation by the develop­ ment of a new industry, which for the next sixty years practically provided the whole of the colony's local income. It was a second attempt, successful this time, at growing New Zealand flax (Phormiun tenax) on a commercial scale and manufacturing its derivatives, fibre and tow. During World Wars I and II, flax fibre commanded such a high price that every available acre was planted to keep the mills supplied continuously. In December 1965, the flax industry finally collapsed - even the British Post Office, which for so long had used only string made from St Helena flax had turned to synthetic fibre. CLOCKWISE FROM TOP: One of the last four remaining St Helena olive trees Nesiota elliptica; the last wild In 1875, J.e. Mellis listed 907 differ­ died in 1994. ent plants to be found on the island. Today, however, only half that number A she-cabbage tree Lachanodes arborea, so rare that the survival of this species might well depend on those is recorded. now planted out in the Sane Valley by the Agriculture and Anyone going to St Helena and who is Forestry Department. particularly interested in the endemic George Benjamin and his beloved ebony trees. flora will, most certainly, meet George Photos: Irina Russell. Benjamin. He grew up driving donkeys for the flax industry before becoming a forest guard for the island's Agriculture and ,Forestry Department in the 1970s creeping plants known as small and the common ancestor of the black cab­ and 1980s. Over the years, he has built large bellflowers. High Peak is frequent­ bage and the St Helena gumwood has up a knowledge of the endemic plants ly shrouded in mist, which can close been discovered on St Helena. The he­ that is matched by no one. Although in and reduce visibility to a few metres cabbage tree (Pladaroxylon leucaden­ he retired in 1995, I was fortunate to within minutes. This is the damp misty dron) now only grows in a few isolated accompany him on a climb up High environment that is favoured by so patches and has large leaves bunched Peak, an area which has the second much of the endemic flora. at the end of each branch. It has small richest concentration of endemic flora The black cabbage tree white and, when in , the after Diana's Peak. There are black cab­ (Melanodendrum integrifo1ium) is a large bunches of leaves resemble cauliflow­ bage trees, he- (but not she-) cabbage tree with bunched fleshy leaves resem­ ers. Its ancestors arrived here more trees, a smaller cabbage tree known as bling a cabbage. It is the most abundant than ten million years ago. It is not whitewood, dogwood (a different natural of the endemic trees and has daisy-like closely related to the she-cabbage tree order from the island's other endemics), flowers that appear in the spring. Nine but, in both cases, remotely similar tree ferns, the St Helena lobelia and the million year old fossilized from plants grow in parts of South America

September 2005 Veld&Flora 139 TOP LEFT: St Helena's central ridge of peaks and New Zealand flax Phormium lenax. The top of Mt. Actaeon (to the right) is marked by a weather-beaten Norfolk Island pine. At the left of the photo is the other ridge, Cuckhold's Point. The highest point, Diana's Peak, is treeless and in the middle. (The names of the three peaks are the subject of one of St Helena's more extraordinary and long-running controversies. The sequence used in this description is that used on the current maps - but as to which is 'correct', there will probably never be agreement).

TOP RIGHT: A he-cabbage tree Pladaroxylon leuca­ dendron.

LEFT: The tree fern Dicksonia arborescens thicket on High Peak. Photos: Irina Russell.

and Australasia. The she-cabbage tree seeds. Very few dogwood seedlings now The small bellflower (Wahlenbergia (Lachanodes arboreal is very rare and grow naturally, perhaps because the angustifolia) is a small prostate plant was re-discovered by George Benjamin destruction of habitats has isolated which grows in crevices and between in 1976. Seedlings are now being plant­ the male trees from the females. The rocks. It has thin stems, narrow leaves ed across the peaks and elsewhere. The tree fern (Dicksonia arborescens) is the and white bellflowers (about 13 mm). leaves are pale green, while the shoots most distinctive of St Helena's endemic The large bellflower (Wahlenbergia lini­ and leaf veins are bright purple-red flora and it grows up to 3 m high, folia) is now very rare and can only be and the small flowers occur as sprays. with large fronds. These tree ferns and found in the wild at High Peak. It grows Whitewood (Petrobium arboreum) has other Dicksonia species in the southern more upright and has bigger white flow­ broad leaves and a small head of six to hemisphere are relicts of thickets from ers than the small bellflower. eight flowers, each about 13 mm long. millions of years ago. The St Helena Historically, the gumwood It remotely resembles some plants from lobelia (Trimeris scaevolijolia) is a large (Commidendron robustum) covered 60% French Polynesia and South America. herb, which likes to grow in the open. of the island, in the 300-450 m zone. In Dogwood (Nesohedyotis arboreal is a It has bright green, leathery leaves and the early years of settlement, however, tall shrub, with lance-shaped, smooth white flowers (about 13 mm) in twos it was the major source of timber and leaves crowded at the end of the shoot and threes. It is very different from the firewood, although the tree reaches only and small bunches of green-white flow­ African lobelia, but distantly related about 6 m with a very crooked form. It ers that turn to black fruits with tiny plants grow on islands in the Pacific. is an umbrella-shaped tree, with hairy,

140 September 2005 Veld&Flora wrinkled leaves and hanging green­ white flowers. Officially, two-thirds of the land on St Helena is classified as There are virtually no islanders who do not under­ barren, with a sprinkling of agaves, prickly pear, enormous cacti and the stand the meaning of the term 'endemic' or who can­ ubiquitous lantana. A few endemics are not recognize a St Helena ebony. to be found, however, such as baby's toes (Hydrodea cryptantha). These are low-growing succulents that exude water when crushed and are easily recognized; in hot weather they dry up, leaving grey skeletons on the ground Two other plants worth mentioning are the ebony and the olive. George Benjamin discovered two examples of the St Helena ebony (Trochetiopsis ebe­ nus), clinging precariously to a cliff in the Blue Point area, in November 1980. This was a major find, as the ebony was nearly extinct by 1771 and was finally presumed to be extinct by about 1850. The plant has been successfully propa­ gated since then and planted back into the wild in places such as Ebony Plain in Thompson's Valley. The ebony is at its best during the winter months (when there is more rainfall), but can flower at any time of the year. The last remain­ ing wild specimen of the St Helena olive (Nesiota elliptical was discovered by George Benjamin in August 1977 on the upper slopes of Mt. Actaeon - it, unfortunately, died in 1994. The total population of St Helena olives (in 1998) stood at four individuals (one vegetatively propagated from the last wild individual and three the offspring of self-pollination from that individual), but can produce no more than very occasional seeds due to a self-incom­ patibility mechanism. In 1994, George Benjamin estab­ lished a small section of staff at the Agriculture and Forestry Department to work on the propagation of the endemic plant species. He also ensured that much of the section's time was spent educating the public and schoolchil­ dren about St Helena's flora. There are virtually no islanders who do not under­ stand,the meaning of the term 'endemic' or who cannot recognize a St Helena ebony. Endemic trees have been estab­ TOP: A black cabbage tree Melanodendrum integrifolium. lished within school grounds to provide ABOVE: Thompson's Valley. Even today, there are few tourists to St Helena since it still can only be reached by informal and accessible seed orchards, sea and then infrequently. Photos: Irina Russell. while sales of endemic seedlings as gar­ den plants to the public have become very popular. The implementation of a management plan to reverse the loss of Further reading the ancient tree fern thicket began in Cross, Tony. 1980. SI Helena. David & Charles, London. April 1995 and includes the removal of The author flax and other invasives, as well as the Irina Russell is a retired Professor of Pharmaceutics, who taught at the University of the Western Cape for twenty­ planting of seedlings such as the large eight years. She is a pharmacist who holds a Ph.D. in Carbohydrate Chemistry from Rhodes University. She is a bellflower and the dogwood. ~ member of the Botanical Society of South Africa.

September 2005 Veld&Flora 141