FLORA & VEGETATION

Since the first botanical expeditions about one hundred years ago Socotra has been famed for its botanical curiosities, but in this paper only a very short view on this fascinating aspect of the archipelago can be given.
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Altogether some 850 plant species have been recorded, about 270 of which are considered to be endemic (ALEXANDER & MILLER 1996), among them strange-looking remnants of ancient floras, which long ago disappeared from the surrounding African-Arabian mainland. According to the World Conservation Monitoring Centre the archipelago is the world's tenth richest island group in terms of endemic plant species.

In general the islands of the archipelago are sparsely vegetated and dominated by xeromorphic forms, which are well-adapted to the harsh climate, such as the desiccating winds of the summer period. Only in sheltered valleys and higher mountain areas is the vegetation more luxuriant (DAVIS et al. 1994, ALEXANDER & MILLER 1996).

Of particular interest are the tree succulents Dendrosicyos socotranus, Adenium obesum sokotranum and Euphorbia arbuscula which have a bizarre appearance, and are typical at the shrubland on the foothills and the limestone escarpments of Socotra.

The members of the family Cucurbitaceae consist mostly of climbing plants, but in Dendrosicyos socotranus they are represented by an elephantine tree growing up to seven meters. Gigantism, is a curious phenomenon of island evolution that may evolve over time in the absence of tall grazing herbivores. Also the Desert Rose (Adenium obesum sokotranum) is characterised by a grotesquely swollen trunk, which keep the trees supplied with water during the summer droughts.

Perhaps the most famous botanical curiosity of Socotra is the dragon's blood tree Dracaena cinnabari, characterised by a mushroom-shaped silhouette. It has related species found in quite disjunct areas, such as north-east Africa and the Canary Islands. They are all relicts of an older flora from the Tertiary period, that once stretched probably from Madeira to the southern part of Russia. Unlike its relatives, which have become very rare, this xerophytic tree is still widespread on Socotra and dominates the evergreen woodland in the centre and east of the island. In legend the tree sprung up from congealed blood shed by a dragon and an elephant as they fought to the death. The red resin from the tree is called cinnabar and was a highly prized product in the ancient world. It is still an important resource for the local people, although it has no longer a great commercial value on the international market. They use it to cure stomach problems, dye wool, glue and decorate pottery and houses, or even as lipstick. Most trees look healthy, although rather old, and like other species on the island, such as D. socotranus, only very few seedlings or young trees can be found, as a consequence of the grazing pressure of livestock.

Incense was another natural product for which Socotra was famous in the past. There are perhaps eight species of Frankincense trees (Boswellia) on the island, some still to be described. In recent times this resin has only played a minor role in export, but on the island it is still used. Very highly regarded in ancient times for medical purpose were also the Socotran aloes. There are three species, all endemic and related. Their bitter, ambercoloured juice is still collected by cutting the leaves at the base and leaving the cut ends to drain onto a goat skin for several hours.