A POTTED HISTORY OF
THE FLORA OF ST HELENA ISLAND
AND ITS CONSERVATION
St Helena has an impoverished but unique flora of 49 endemic (found on St Helena and nowhere else in the world) species of flowering plant and 13 endemic species of ferns. Thisflora has been eroded due to the extinction of at least six species since the arrival ofman on the Island.
Discovered by the Portuguese in 1502, goats were soon introduced to the Island togetherwith citrus trees and herbs to provide vital provisions for passing ships returning toEurope from the East. These introduced species had a massive destructive impact on thenative flora and fauna of the Island. Very quickly the goat population swelled to numbersin the thousands, browsing the vegetation, barking trees and preventing regeneration.Increasing fragmentation of the Islands woods was caused in the 16 th and 17th Centuries,the Island having previously been described as having a covering of “fine trees”and “big timber”.
Even further environmental damage was to be caused when the Island was eventuallypermanently settled by the British in 1659. Woods previously fragmented by over-grazingwere now destroyed for timber for fuel, building and clearance for pasture land. The barkof the endemic Redwood tree, Trochetiopsis erythroxylon, was used for tanning the hides ofcattle such that within 60 years of settlement the tree had almost been brought toextinction.
Originally heavily forested, the steep and rugged landscape of St Helena became almostcompletely denuded of vegetation. Wood was so scarce that species had to be introduced,like the European gorse bush and pine trees. Unusual species like the Boxwood, Stringwoodand Burchell’s Bellflower were forced into extinction alongside other species of birds andinvertebrates, never to be seen again. Species like the giant earwig, the world’s largest,a species occupying the damp environment of the gumwood forest floor has not been seen forover thirty years nor, the giant ground beetle of the drier scrubland. With both habitatslost it is likely that both species are now extinct.
Over two thirds of the Island are classed as barren Crown Wastes. Goats remained on theIsland in large numbers, after various failed attempts to control their numbers, until the1960s. Happily, the regeneration of the vegetation since this time is obvious to those whowere witness to the state of the Island prior to this. However the species quickest toregenerate and colonise the Crown Wastes are exotic introduced species: Prickly Pear,Lantana, Chrysanthemoides sp, Olea africana, Schinus terebinthifolia… Inland the storyis a little different, introduced timber species replaced the endemic trees, endemicvegetation was cleared for pasture land and later for flax, Phormium tenax, for the flaxfibre industry and arable land. Exotic species introduced as ornamentals have spread intothe last strongholds of endemic vegetation along the Island’s sickle shaped central ridge,causing the decline and extinction of the flora of the high moist altitude vegetation byinvading their habitat niches.
The original vegetation of the Island has been reconstructed using past records androughly divides into seven main vegetation types. These habitats together with the endemicand indigenous species which they once contained are described in brief below. (The mapbelow shows just 3 zones – the dry outer zone [sea level to 400 m] – the medium altitudezone [400 to 600 m] – the peaks zone [600 to 820 m]/J Ekwall).
1. Tree fern thicket (c. 700- 823 m)
Endemic tree ferns, Dicksonia arborescens, dominate the moist, mist engulfed vegetationzone occupying the highest elevations across the Island’s central ridge. The spreadingBlack Cabbage Trees, Melanodendron integrifolium also endemic to the Island, with theirdaisy like flowers are another dominant species together with ferns. The tree fern thicketis the only vegetation type that can still be found to any great extent on the Islandtoday. Yet this is still under constant threat from invasive weeds.
2. Cabbage tree woodland (c .600 – 750 m)
So called cabbage tree because of their leaves which form rosettes at the tips ofbranches. Largely Composite species or tree daisies, unique only to St Helena.
3. Moist gumwood woodland (c. 500 – 650 m)
Another species of Composite, the Gumwood, Commidendrum robustum, dominated thishabitat. Gumwoods came under intense grazing pressure and their wood used for fuel andtimber. Today only fragments of this type of woodland remain.
4. Dry gumwood woodland (c. 300- 500 m)
Dominated by the more drought tolerant gumwoods, the afore mentioned Gumwood and theBastard Gumwood, Commidendrum rotundifolium. This habitat has been completely destroyed,only a few gumwoods remain in cliff refuga and the Bastard Gumwood has become extinct inthe wild: only to be known from 19 specimens.
5. Ebony – gumwood thicket (c. 100 – 500 m)
On the drier and more rocky parts of the Island, particularly the western side thicketsof small Ebony trees and gumwoods are thought to have co-existed. The Ebony, an endemicspecies to St Helena completely unrelated to the ebony that most people would immediatelyrecognise, covered a huge area across this habitat type. Place names such as Ebony Plainand historical records and stories give evidence to this. Once used in great abundance forburning in lime kilns for the production of mortar for building, this dense black wood wasquickly over-exploited. Soon only the stumps of trees were to remain and even these to hadtheir use in the local in lay craft. Today only two small bushes survive on a precipitouscliff. Cuttings collected from these trees have been successfully propagated and cuttingsand seed have been planted back in many areas.
6. Scrubwood scrub (c. 0 – 350 m)
On the outer parts of the Island with very low precipitation, exposed to wind andsalinity the Scrubwoods, Commidendrum rugosum, were the dominant species. These small lowgrowing and spreading shrubs with large daisy like flowers are highly palatable to goatsand this habitat was heavily browsed until little remained. Together with theEbony-Gumwood thicket these former habitats constitute the barren Crown Wastes. Today withthe removal of goats from the Crown Wastes the scrubwoods and other endemic and indigenousspecies associated with this habitat are making a recovery.
7. Saline semi-desert (c. 0 – 250 m)
In areas of saline soils the St Helena Tea Plant, Frankenia portulacifolia and theindigenous Samphire, Suaeda fructicosa, were the dominant species although the scrubwoodwas associated with this habitat. Also browsed almost to extinction the species of thishabitat are making a recovery. The most successful being the halophytic Babies’ Toes,Hydrodea cryptantha, which is now spreading back in large numbers over much of the outerparts of the Island.
Conservation efforts to save St Helena’s endemicand indigenous species and habitats.
The Environmental Conservation Section of the St Helena Government Agriculture andForestry Department is responsible for working towards the conservation of St Helena’sunique habitats and species. Working from their base, the Endemic Nursery, these rare andendangered plant species are propagated for re-introduction back into the wild – wherethat is there is some wild’! Species recovery programmes are on-going, particularly forthose species so reduced in numbers that they would not survive without intervention andmay have genetic and reproductive problems.
In March of this year (1996) St Helena’s first National Park was proclaimed. The Diana’s Peak National Parkcovers and area of 64 hectares across three of the main peaks along the central ridgewhere the last vestiges of tree fern thicket remain. The battle has now begun to reversethe invasion of exotic alien plant species such as: Buddleia, Buddleia madagascariensis,Bilberry, Solanum mauritianum, flax, Phormium tenax and Whiteweed, Eupatorium pallidium,and restore the tree fern thicket and cabbage tree woodland.
In the local St Helena news paper each fortnight, we are publishing fact sheets abouteach of the endemic species of flowering plant. I have reproduced the first of these herefor you to find out a little bit more about St Helena’s fascinating flora.
For further information you can always write to us here on St Helena,care of:
The Environmental Conservation Section, Agriculture and ForestryDepartment,Scotland, St Helena, South Atlantic Ocean.
List of endemic flowering plants and ferns of StHelena
Drawings by Muriel G Williams and Richard LGillett
Updated November 19 1998.