Table 31 Succulent flora of Ethiopia

Aizoaceae

Aloaceae

Asclepiadaceae Cactaceae

Crassulaceae Cucurbitaceae

Euphorbiaceae

Geraniaceae

Passifloraceae

Piperaceae Portulacaceae

Vitaceae

Seven genera and perhaps 13 species, only 3 or 4 species of Delosperma are of horticultural interest. Only 1 of these, D.nakurense, is relatively well known.

38 species of Aloe, 22 endemic, mostly at higher altitudes, some known from rather few localities, but none vulnerable and some extremely abundant.

Many non-succulent.

Rhipsalis baccifera native to south-west forests; Opuntia at least 3 species growing as weeds, one exploited locally for fruits.

Ethiopia has the greatest number and diversity of Sedum spp. of any African country (Gilbert 1985).

Most species not succulent; Momordica rostrata and Cephalopentandra ecirrhosa with well-developed succulent caudexes, and Mukia pallidinervia a true leaf succulent.

Three genera include succulents: Euphorbia, Monadenium, and Jatropha. Euphorbia is the largest genus within Ethiopia, and also includes the largest number of succulents. The exact number depends largely on what definition is used for succulence, there being a number of marginal species. The largest group are the 45 species, 15 endemic, belonging to the all succulent subgenus Euphorbia; subgenus Lacanthis has 4 species, 3 endemic; subgenus Esula has 3 good succulents plus a number of marginal succulents,

Most species of Pelargonium at least slightly succulent; only one of the Ethiopian species, P. boranense, a local endemic from southern Ethiopia, of interest to general collectors because of the succulent stem and very large bright red flowers.

Two species of Adenia having true succulents - A. venenata and A. aculeata; others subsucculent, most notably A. ellenbeckii, or not succulent.

Eight species of epiphytes, none endemic, all widespread in Africa and sometimes further afield.

Talinum: 3 species, 7. portulacifolium common and widespread; Calyptrotheca somalense at least locally common in western Sidamo and Gamo Gofa - apparently with a short flowering period and probably under-recorded; Portulaca: 15 species, some rather poorly known, others widespread, including a troublesome pantropical weed.

Most non-succulent, no succulents endemic, some species of Cissus leaf-succulents (C. rotundifolia) or stem succulents (C. Cactiforme, C. quadrangulare.C.quinquangulare): Cyphostemma betiforme a stem succulent restricted to gypsum areas of the south-east.

and there is no doubt that most these would be very vulnerable to any kind of commercial collecting. It is vital that such exploitation should be very strictly controlled.

Agriculture — Habitat degradation from agriculture is obviously a threat to many succulents, but it is probably not of very great importance within Ethiopia. Most species are found in areas not suitable for cultivation and indeed some species, most especially some of the more shrubby Aloe species, have probably extended their ranges in parts of the country where denudation by erosion following cultivation has created extensive open rocky slopes.

Overgrazing — Overgrazing is a problem in some areas, but in many cases succulent species survive surprisingly well wherever there is some protection by rocks and unpalatable shrubs.

Introduced species — Opuntia cf. dillenii and two or three other species are a major weed problem in some areas but there is some evidence to suggest that native succulents are at least sometimes able to benefit from the shelter these spiny plants can offer.

Conservation status of succulents

A comprehensive listing of the conservation status of Ethiopian succulent plants has not yet been prepared. WCMC holds records of 76 nationally threatened succulent species of Ethiopia.

Existing conservation measures

Most major conservation areas have been identified and provisional or nominal protection implemented. Ethiopia's protected areas consist of national parks, sanctuaries, wildlife reserves, and controlled hunting areas. Only two national parks, Awash and Simen Mountains, have been legally gazetted.

All the national parks contain some succulents. Political upheavals and lack of resources have made the effectiveness of these parks open to question, but there is no doubt that they will offer some protection from agricultural development, probably the greatest overall threat to succulents within Ethiopia. The Semien Mountain National Park includes the type localities of many Ethiopian high-altitude endemics including Rosularia simensis, Hypagophytum semiense, and probably Aloe steudneri. Awash National Park includes the type localities of Pachycymbium sacculata and Euphorbia awashensis. Quite a number of other succulents also occur within this park.

The Mago National Park, which is not yet gazetted, has Euphorbia grandicornis, E. scoparia, Sansevieria spp, and Adenium obesum. Nechisar National Park, also not yet gazetted, has fine stands of Euphorbia tirucalli.

Somalia

Somalia has approximately 3000 flowering plant species of which about 500 are endemic. Highly specialised vegetation types within the country support many endemic xerophytic plant species suggesting that arid climatic conditions have remained unchanged for long periods of time.

The vegetation of Somalia consists mainly of Acacia-Commiphora deciduous bushland and thicket particularly in the south. There are large areas of semi-desert grassland and deciduous shrubland in the north and extending south along the coast.

The north-east of Somalia (Cal Madow mountains) is particularly rich in succulent plant diversity and is considered to be an internationally important centre of plant biodiversity (WWF and IUCN 1994). Specialised limestone habitats, with outcrops of pure gypsum, harbour many endemic species. Some of these species have been known only from single collections by early naturalist explorers and many others have only been discovered in the past fifteen years. The bush-covered plains of southern Somalia have succulents in common with south-east Ethiopia and the better-known region of north-east Kenya. There are also local endemics confined to isolated coastal outcrops or coastal dunes.

Threats to the succulent flora

Desertification threatens species of the succulent scrub. Somalia has the greatest proportion of pastoralists in Africa, and livestock accounts for 40 percent of the country's GNP. Overgrazing is the dominant threat to natural habitats and the succulent species which they contain.

Some succulent species are able to withstand grazing pressures. Aloe spp. are, for example, generally unpalatable. Aloe mcgalacantha invaded extensive areas following removal of woody vegetation by livestock, for example, on the plains surrounding the war-stricken city of Hargeisa. Other species of Aloe, such as A. pirottae and A. peckii are, however, adversely affected by grazing pressures. These two species only grow in the shelter of bushes and once the vegetation is removed the species become progressively rarer. Other succulent species are particularly susceptible to grazing pressures, for example, Asclepiads which are not spiny or protected by poisonous substances. Euphorbia columnaris, endemic to a small area in north-east Somalia is almost extinct because overgrazing has led to soil erosion. Plants of the species have weak root systems which are unable to support mature plants once the soil is eroded.

War in the Horn of Africa has lead to the disruption of traditional grazing regimes leading to further environmental instability. The flow of refugees into northern Somalia has lead to destruction of vegetation for kilometres around the camps (Hutchison 1991).

Table 3.2 Succulent genera of Somalia

Family

Genus

No. of

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