Relict of ancient African tropical forests
Saint Helena rose above the sea level some 14 million years ago and last volcanic activity took place some 8 million years ago. Over this long time period here have evolved specific species of plants and animals not met anywhere else in the world.
Before the coming of people nearly all the plants which were growing on the island were endemic. It is possible that on Saint Helena island we see relicts of African flora and fauna.
Even more interesting – it is possible that different ecosystems on the island represent relicts of African flora from different times.
The oldest are tree fern thickets on the summits of the highest hills in the island. These thickets could be similar to the moist tropical forests which grew in Africa in the Miocene epoch, some 10 million years ago. The humid climate around the summits of Saint Helena helped to preserve these species, while Africa itself became drier and only on the summits of higher African mountains has survived somewhat similar flora.
Endemic plants and animals
On Saint Helena island have been found 10 endemic genera of plants – and six of these genera and most of endemic plant species are found only in the tree fern thicket. Here are found 14 species of ferns which are not found anywhere else in the world. Some of the endemic species in the fern thicket are:
- Black cabbage tree (Melanodendron integrifolium). Seedlings of this tree grow on the trunks of tree ferns.
- Petrobium arboreum – whitewood, one of tree species.
- She cabbage tree (Lachanodes arborea) – found only in a single patch.
- Sium burchellii – dwarf jellico, grows only in a tiny patch.
- St. Helena dogwood (Nesohedyotis arborea) – now very rare, only 147 individuals of this tree are known.
- St. Helena olive (Nesiota elliptica) – now grows only in captivity, outside the park.
- St. Helena tree fern Dicksonia arborescens.
- Wahlenbergia linifolia – large bellflower, now found only in a tiny patch.
Here are found many endemic species of fauna as well, such as:
- Blushing snail (Succinea sanctaehelenae) – small terestrial snail, which is found in many places around the island but is most common in fern thicket.
- Loveridge’s hoverfly (Loveridgeana beattiei) – this insect depends on flowering of the endemic trees. If any these trees will go extinct, hoverfly will die as well.
First national park in Saint Helena
Largest patches of tree fern thicket remain around the summit of the highest peak of Saint Helena island, the 818 m high Diana’s Peak.
The indigenous vegetation of the lower parts of island was largely eliminated by the 1750s, but tree fern thicket further up in the hills was largely intact until the 1850s. Then these forests were replaced by the plantations of New Zealand flax, introduced plants spread further into the forest. Now the remaining parts of fern thicket (only 15.7 ha!) are very endangered, there are ongoing constant activities to eradicate alien plants in this area.
Around the Diana’s Peak in March 1996 was created the first national park in Saint Helena. It is very small, if compared to the better known national parks around the world – just 81 ha. But this small microcosm provides endless opportunities to scientists and numerous impressive sights and experiences to tourists.
- Smith, Doug. A Rescue Plan for the Threatened Tree Fern Thicket of Diana’s Peak National Park, St Helena. 1996. Accessed in the 1st September 2013.
|Coordinates:||15.9728 S 5.7001 W|
|Address:||Africa, Saint Helena, central highlands|
|Area:||81 ha (national park), 15.7 ha (stands of intact tree fern thicket)|
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