Socotran Plants

The Socotra Archipelago boasts a rich flora, remarkable endemic species and plants with a long history of traditional use. With a total of 835 vascular plant species, 308 (37%) are endemic. There are also 74 bryophytes; one hornwort, 30 liverworts and 43 mosses, 6of which are endemic (Kürschner, 2003).

The islands have a diverse geology and a climate that varies between areas, creating a diversity of ecosystems. Dense evergreen and semi-evergreen woodland can be found in wet and sheltered areas, but there are also drought-adapted plants surviving in desert-like landscapes.

Because of such high diversity and endemism in plants, the islands have been declared a WWF Global 200 Ecoregion, a Plantlife International Centre of Plant Diversity and are included in the Horn of Africa Biodiversity Hotspot. These are added to designations of UNESCO World Heritage Site and UNESCO Man and Biosphere Reserve.

There are many endemic species that are famous and remarkable, both to botanists and keen amateurs alike. The dragon’s blood tree, Dracaena cinnabari (Ruscaceae), is named after the blood-red sap that exudes from the trunk when cut. This has been used traditionally as a medicine and a cosmetic. The trees are slow-growing and long-lived (possibly a few hundred years), and in maturity the crowns have an upside-down umbrella shape. The dense Dracaena woodland found at Firmihin is globally unique – no other arborescent (tree-forming) Dracaena species are found in woodland as they are on Socotra.

Dracaena cinnabari (Ruscaceae) at Firmihin, Socotra; a globally unique landscape.

Photo: Lisa Banfield, RBGE

The desert rose Adenium obesum subsp. sokotranum (Apocynaceae)is one of the most famous of the Socotran bottle-trees; trees that store water within their trunks to help them survive the more arid environments of Socotra. The Socotran subspecies can grow much larger than the mainland subspecies, reaching 5 m in height, with huge, swollen trunks that give them their name, obesum (obese). Desert roses are scattered throughout Socotra, but are perhaps best observed on the limestone plateau of Dixsam where they can dominate the landscape. Often at least one individual can be seen flowering; when many flower, it is said to predict the coming of the rains.  

The Desert Rose Adenium obesum subsp. sokotranum (Apocynaceae)

Photos: Lisa Banfield & Patrick Home Robertson, RBGE

Dorstenia gigas of the fig family Moraceae is another famous endemic Socotran bottle tree. Again, it is much larger than other species of Dorstenia, reflected in its species name ‘gigas’ meaning ‘giant’. These trees can be found scattered across Socotra, where they can be seen almost magically growing from cliffs and rock-faces.

Dendrosicyos socotranus is one of the largest trees in Socotra. It is the only tree-forming species of the cucumber or gourd family, Curcurbitaceae, sometimes reaching above 6 m in height. They are found throughout the lowland, drier areas.  

Dendrosicyos socotranus, the only tree species of the Cucurbitaceae family

Photo: Steve Scott, RBGE

Socotra has a high diversity of Boswellia (Burseraceae) species; trees that produce frankincense or olibanum, an incense which has been traded for some 5000 years for use in religious ceremonies and medicine. Out of a total 24 species, 7 are endemic to the Socotra Archipelago. Some species grow only on rocks and cliff faces, others only from the ground. The tallest species are Boswellia elongata, many of which are found at Homhil, and Boswellia ameero, which is common at the higher altitudes of the walking route from Wadi Ayheft to the Meqadrihon Pass.

Boswellia ameero (Burseraceae), one of the 7 species of Boswelliaendemic to the Socotra Archipelago

Photo: Lisa Banfield, RBGE

Punica protopunica (Punicaceae) is another notable endemic tree species. It is the only known relative of the widely-grown pomegranate tree, and scientists have been uncertain where these species fit within the plant classification system. Dirachma socotrana (Dirachmaceae), with one known relative found in Somalia, has been referred to as a ‘living fossil’ due to its unique combination of floral characters.

Tree species are often the most appealing to many people, but the Socotra Archipelago also has some remarkable and beautiful smaller plants, including many succulents such as Caralluma socotrana, 5 endemic species of Echidnopsis, and 2 endemic genera with a single species, Duvaliandra dioscorides and Socotrella dolichocnema (all Asclepiadoideae, Apocynaceae), and 3 endemic species of Aloe(Aloaceae).

Succulent species of Socotra: (left) Echidnopsis bentii, endemic; (centre)Caralluma socotrana; (right) Duvaliandra dioscorides, endemic

Photos: Lisa Banfield, RBGE

Threats and Conservation

Although the Archipelago is in better condition than many other island ecosystems, the flora of the Socotra Archipelago does face some very real threats. Many tree species are suffering from a lack of regeneration, possibly caused by climate change or overgrazing. Overgrazing is also leading to loss of vegetation cover and serious soil erosion in some areas.

Traditional land management practices are becoming less adhered to as the culture of the island changes, which could lead to overexploitation of some species. Illegal plant collecting threatens sought-after plant species, in particular rare succulents such as the critically endangered Duvaliandra dioscorides (Asclepiadoideae, Apocynaceae). These rare species fetch a premium in western plant markets so they can be added to an individual’s private collection.

If climate change causes increased aridity, as some predict, this will threaten many endemics. Large-scale infrastructure projects, such as road building, are damaging habitats as well as the aesthetic beauty of the island. Although there are some potentially invasive species present, they are either being actively controlled by SCDP/SGBP project or are confined to the heavily-grazed, degraded areas around the main town of Hadibo. However, the potential for invasion of alien species is increasing as Socotra has more and more contact with the outside world.

IUCN Status of Endemic Vascular Plants of the Socotra Archipelago:

Royal Botanic Garden in Edinburgh and others continue working with SCDP/SGBP to describe, survey and monitor the vegetation of Socotra. Populations of endemic and endangered plants are being established at Adeeb’s nursery, just outside Hadibo, both as an educational resource and an ex-situ conservation collection.

Watering in Adeeb’s nursery 
 

Photo: Bohdana Rambouskova, SGBP

Plant Spotting on Socotra

Many of the local guides of Socotra have a good knowledge of the most famous plants and where to see them. If you are visiting Socotra specifically to see the plants, and you have particular requirements, SGBP can help you find the right person. Adeeb’s nursery is a must-see for any plant enthusiasts for a close-up view of many endemic species and a source of further information.

Please respect the local culture, and be aware that it is illegal to remove any plant material from Socotra, including seeds.

Further Information:

CHeung, C. & DeVantier, L. (2006). Socotra: A Natural History of the Islands and their People. K. Van Damme (Ed.). Hong Kong: Odyssey Books and Guides, Airphoto International Ltd., Hong Kong. 408 pp.

Kürchner, H. (2003). Nineteen new records to the bryophyte flora of Socotra Island. Additions to the bryophyte flora of the Arabian Peninsula and Socotra 5. Willdenowia.33: 445-458.

Miller, A.G. & Morris, M. (2004). The Ethnoflora of the Socotra Archipelago. Royal Botanic Garden Edinburgh.

Lisa Banfield, Royal Botanic Garden Edinburgh