Mediterranean acacia-argania dry woodlands and succulent thickets
The Mediterranean acacia-argania dry woodlands and succulent thickets lie along the Atlantic Moroccan coast and extend to the easternmost Canary Islands. This ecoregion contains considerable species diversity. While the mainland portion of this ecoregion hosts a diverse fauna, with a mixture of Palearctic and Afrotropical species, most endemic species are found on the ancient, low-lying Canary Islands of Fuerteventura and Lanzarote. The two disjunct portions of this ecoregion also differ in their socioeconomic attrubutes and conservation priorities. Governed by Spain, the Canary Islands have a well-established system of protected areas, but biodiversity is threatened by the intensity of ongoing tourism. In Morocco, the protected area system is still being expanded and strengthened, while these woodlands are a vital resource for rural people. The management of argan tree woodlands provide an estimated two million people with argan oil, pasture, honey, charcoal and construction materials; argan oil is a particularly important cash crop for local peoples.
Location and General Description
The Mediterranean acacia-argania dry woodland and succulent thicket ecoregion falls chiefly within Morocco, extending into the northwestern corner of Western Sahara. The ecoregion also covers the two easternmost Canary Islands of Fuerteventura and Lanzarote as well as numerous associated islets (e.g. Graciosa). Although not mapped, this ecoregion extends into the Algerian Northern Sahara (Tindouf – close to the border with Morocco Benmalek and Brac de la Perrière, unpubl.). On the African mainland, the ecoregion occupies the Atlantic coastal plain, the lowlands of Haouz-Tadla, the Souss and Draa River valleys, and the western end of the High and Anti-Atlas Mountains.
Compared to the rest of the Canaries, the eastern Canary Islands have lower elevations, and are older, estimated to be 16 to 20 million years old. The Canary Islands are volcanic in origin but neither of these two islands are still active. The landscape is less rugged than the other islands in the archipelago, and the highest point only reaches 807 meters (m). On the mainland, the ecoregion is relatively flat and below 800 m; the increased elevation towards the Atlas Mountains in the east marks the border of this ecoregion with that of the Mediterranean Woodland and Forest ecoregion. The rocks on the mainland are varied and include Cretaceous to Tertiary Age calcareous and sandy deposits. The soils are throughout the region are relatively nutrient poor.
Climatically, the ecoregion is sub-tropical, with mild, frost-free winters and relatively cool summers due to the moderating influence of the sea (especially on the Canaries islands). Generally, rainfall is between 100 and 500 millimeters (mm) per year, and it can be less than 100 mm in the Algerian part of the ecoregion where it falls as low as 50 mm. The mean annual temperatures are constant, ranging between 18ºC and 20ºC. This stability is due to the ecoregion’s proximity to the Atlantic Ocean. Maximum temperatures can reach 50° C further inland in this ecoregion, closer to the Sahara Desert.
Argania spinosa forest and Euphorbia-dominant succulent shrubland are the predominant vegetation types in the ecoregion. The endemic Argania spinosa woodlands cover an area of about 6500 square kilometres in the southwest of Morocco. The climatic area of this ecoregion estimated by Boudy was 21,280 square kilometres.
The major plant species which develop with Argania are: Periploca laevigata, Senecio anthephorbium, Launaea arborescens, Warionia saharae, Acacia gummifera, Rhus trpartitum, Withania frutescens, Euphorbia officinarum, Cytisus albidus, Ephedra altissima, and Tetraclinis articulata. The boundaries of the ecoregion correspond to those of the boundaries of the Argania forest. Acacia gummifera grows in shrubs and is a common companion species to the argan tree. Other acacias such as Acacia raddiana and Acacia ehrebengiana are more prevalent in the inland part of the ecoregion, and are widely distributed through out the Sahara Desert. Balanites aegyptiaca and Maerua crassifolia commonly grow among Acacia-Argania woodlands in the eastern part of the ecoregion.
Further inland, areas of argan forest merge into stands of succulent Euphorbia. Three succulent and two dendroid species of Euphorbia occur in the southwestern corner of Morocco, and except for Euphorbia resinifera, are most highly developed close to the sea where mists are frequent and summer temperatures are ameliorated. On the Canary Islands the flora is more diverse and includes more endemic species than the portion of the ecoregion on the mainland. In Algeria, the cover of Argania woodlands is related to the temporary riverbeds. Argania occurs with Launaea arborescens, Kleinia anteuphorbium, Warionia saharae, Euphorbia balsanifer and Acacia gummifera.
The population density of the ecoregion is quite low, but some agriculture is possible close to the coast if freshwater is available. On Fuerteventura the human population density is eleven people per square kilometre.
Biodiversity Features
The Canary Islands portion of the ecoregion has more biological features of interest than the mainland. It is an important area for plant endemism. As a whole, the islands contain approximately 500 endemic plant species and 20 endemic genera. Within this ecoregion, the islets between the lava-covered terrain in Timanfaya National Park support three species of plants which are endemic to Lanzarote: Echium pitardii and Asteriscus intermedius. On the coastal dunes of these two islands, local endemics, such as Androcymbium psammophilum, and North African plants, such as Traganum moquinii, are also found. Recently, a new subspecies of the Canarian Islands: Dracaena drago has been discovered on the African mainland, named Dracaena drago ajgal. This is a relict species that only grows in a very small area known as the Massa River Canyon (in the Occidental Anti-Atlas, Morocco) in the middle of this ecoregion. Despite the small area, several thousands of individuals have been recorded, resulting in the best preserved patch of this species remaining.
The Canarian shrew (Crocidura canariensis, VU) is the only mammal endemic to the Canary Islands portion of this ecoregion. In addition, both the East Canary gecko (Tarentola angustimentalis) and the Haria lizard (Galiotia atlantica), and its subspecies G. a. atlantica, are endemic to the two larger islands and associated smaller islets in the eastern Canaries. The island portion of this ecoregion is important for endemic birds. It contains the endemic Furteventura chat (Saxicola dacotiae), and the following endemic bird sub-species: kestrel (Falco tinnunculus dacotiae), houbara bustard (Chlamydotis undulata fuertaventurae), barn owl (Tyto alba gracilirostris), stone-curlew (Burhinus oedicnemus insularum), and the cream-colored courser (Cursorius cursor bannermani). In addition, there are a number of Canary Islands endemic species and subspecies shared by this ecoregion and the Canary Islands Dry Woodlands and Forest. These include the endemic species Apus unicolor and Anthus berthelotii, as well as a subspecies of buzzard (Buteo buteo insularum), spectacled warbler (Sylvia conspicillata orbitalis), great grey shrike (Lanius excubitor koenigi), lesser short-toed lark (Calandrella rufescens polatzeki), and linnet (Acanthis cannabina harteri).
The invertebrates of the islands have not been well studied and are poorly known. A subspecies of the green-striped white butterfly (Euchloe belemia hesperidum), found on Fuerteventura, is the sole endemic butterfly in the Canary Islands portion of this ecoregion.
The mainland portion of the ecoregion also possesses a number of endemic plant species, which are related to the Macaronesian flora on the Canary Islands. However, this area is less important for plant endemics than the Canary Islands. The [[coast]al] portion of Africa also contains plant species with more widespread distributions, including those found more typically in the Palearctic, and those that are more typically in the Afrotropics. Argan woodlands perform multiple environmental roles, particularly in soil erosion prevention, providing shade and shelter from the effects of extreme evapo-transpiration, water filtration and aquifer replenishment facilitation and, overall, in buffering the region from desertification.
On the mainland the fauna comprises a mixture of Palearctic, Afrotropical and locally endemic species. Recorded mammals include ratel (Mellivora capensis), European wildcat (Felis silvestris), mongoose (Herpestes ichneumon), Barbary ground squirrel (Atlantoxerus getulus), North African elephant shrew (Elephantulus rozeti), Hoogstraal's gerbil (Gerbillus hoogstraali, CR), Barbary striped grass mouse (Lemniscomys barbarus), and wild boar (Sus scrofa). Two rare predatory species in this ecoregion are the caracal (Felis caracal) and the African wildcat (Felis silvestris lybica) while two species of gazelles, dorcas and Cuvier’s (Gazella dorcas, Gazella dorcas, VU and Gazella cuvieri, EN), and the Barbary sheep (Ammotragus lervia, VU) are under threat of extinction in this ecoregion. The European otter (Lutra lutra) has been sighted, but is extremely uncommon.
There is one particularly important bird species. The Souss-Massa National Park area includes an important breeding population of a near-endemic bird, the bald ibis (Geronticus eremita, CR), which is found in this ecoregion and in one or two other arid parts of the Mediterranean Basin and the Middle East.
A notable amphibian found in the ecoregion is the Tiznet toad (Pseudepidalea brongersmai). Subtropical faunal species such as the African egg eating snake (Dasypeltis scabra), the Senegal earth squirrel (Xerus erythropus), and the dark chanting goshawk (Melierax metabates) have been recorded in Essaouira. The butterflies of this area include a number of palaeoendemic species, relicts from the Tertiary period. Threatened butterfly species include the Spanish festoon (Zerynthia rumina), Mediterranean tiger blue (Tarucus rosaceus), desert orange tip (Colotis evagore), and Mediterranean skipper (Gegenes nostrodamus).
Current Status
There has been a considerable loss of habitat throughout the Canary Islands since Europeans colonized the area in the 15th century. Habitats here are also naturally fragmented due to their distribution on different islands within the archipelago. Within each of the islands, remaining habitats are fragmented to a greater or lesser extent depending on climatic conditions and the history of human occupation and use. The habitats on the islands in this ecoregion, (Fuerteventura, Lanzarote), and the smaller islets, including Graciosa, are much less fragmented than their western Canary counterparts because they have fewer inhabitants and have a more arid climate, which is generally unsuitable for agriculture. Unfortunately, they have been badly affected by overgrazing. Despite this, the recent past has seen an increase in conservation and protection efforts, stimulated by a huge increase in tourism to the Canaries. Although tourism has resulted in over-use and degradation of some areas, the comprehensive system of protected areas has served to more or less stabilize the conservation situation on most islands.
In Morocco, the argan tree makes up about seven percent of the total forest cover and has exceptional ecological and socio-economic values. Constituting a multi-use silvo-pastoral system, argan woodlands are managed for a large number of products, such as oil, pasture, honey, charcoal and construction wood. This management ensures the subsistence of two million rural Moroccans. The argan is also a valuable shade producing tree and is important for soil conservation. In the region of Essaouira, argan oil production is between 1000 to 2000 tons per year. In spite of its importance, 20 square kilometres were cut each year for urban expansion and development during the period 1918 through 1924. Since 1925, the species has been protected by a law, which regulates the rights of use by local people. Despite this, argan woodlands suffer from continuous degradation due to the abandonment of traditional management practices and the intensification of their use. The movement of large animal herds to the argan woodlands upset the already delicate situation, and currently the loss of these woodlands is estimated at six square kilometres per year. During the last 20 years, intensive farming activities under the Arganian trees have been increasing, mainly in the Souss region.
When compared to habitat loss (Land-use and land-cover change) on the Canary Islands, the loss of habitat on the mainland has been less severe as there are fewer people and the remaining areas are more extensive. Even so, the best remaining areas of habitat are now found in National Parks and other protected areas. Of prime importance is the Souss-Massa National Park, which includes the Oued Massa Biological Reserve. In 1987, the area of Souss-Massa was projected at 720 square kilometres, with 42,000 Hectares (ha) under strict protection. The Khnifiss/Puerto Cansado area is a RAMSAR and Biosphere Reserve site, primarily for its wetland values. Given the importance of this ecoregion to Morocco socio-economic development, the argan ecosystems have been declared as a "Man and Biosphere Reserve (MAB)" by the UNESCO under the request of the government of Morocco. A management plan and a zoning is being prepared for the MAB Reserve. The Arganeraie Biosphere Reserve was established in 1998 and was the first of its kind in Morocco. It includes argan woodlands in addition to urban and agricultural areas. Two cooperatives have been set up as part of this biosphere reserve, one for fisherman and the other for women to produce Arganian oil. The ecoregion is protected through an extensive system of protected areas on the Canaries, including Timanfaya National Park as well as the large Islotes y Famara, Pozo Negro and Jandîa Nature Parks.
Types and Severity of Threats
In Morocco, overgrazing and over exploitation of the argan trees are extremely serious threats to the natural vegetation throughout the ecoregion. Poor agricultural practices are also a threat to the vegetation and species of the ecoregion, particularly in the wetter areas which are the most suitable for agriculture. Introduced plants have invaded the xerophytic communities on the lowland and have often replaced the natural Euphorbia-rich vegetation.
Non-native species are a serious problem on the Canary Islands, and the introduction of some species of fauna (squirrel, rabbit, mice, cats) has posed a serious threat to several of the endemic animals, and to the breeding seabirds. On the Canary Islands, the rapid increase of tourism poses numerous risks to the habitats. The use of off-road vehicles on the dunes of Fuerteventura and in the south of Lanzarote at Playa de los Papagayos has badly damaged the dunes and the vegetation of these areas. Finally, land speculation for tourism and for local second residences is also problematic.
Justification of Ecoregion Delineation
The Mediterranean acacia-argania dry woodland and succulent thicket is distinguished because of its distinctive flora. Argania spinosa is the only member of the tropical family Sapotaceae to occur on mainland Africa north of the Sahara where it forms dense forests with a shrubby understory. The linework reflects a combination of White’s vegetation units, including the southwestern portion of the ‘semi-desert grassland and shrubland’, an Argania transition zone, and an anthropogenically influenced landscape where the potential vegetation would have been this type of woodland. The eastern two Canary Islands (Lanzarote and Fuerteventura) were included with the Acacia-Argania woodland, as the lower-lying and more arid nature of these islands make them more similar to the mainland ecoregion than to the dry woodlands of the other islands.
Reference
- Charco, J. 1999. El Bosque Mediterraneo en El Norte de Africa. Biodoversita y lucha contra la desertificacion. Agencia espagnola de cooperatioon internacional Madrid
- Clarke, T. and D. Collins. 1996. A birdwatcher’s guide to the Canary Islands. Prion Ltd. Perry, Cambs, UK.
- M’Hirit, O., M. Benzyane, F. Bencherkroun, S.M. El Yousfi, and M. Bendaanoun. 1998. L’arganier. Une espèce fruitière-forestière à usages multiples. Edition Pierre, belgique, 144 p. ISBN: 2870096844
- Ministère de l’Agriculture et de la mise en valeur agricole, 1992. Plan Directeur des Aires Protégées. VOL I, II. Royaume du Maroc
- Peltier, J.P. 1983. Les séries de l’arganeraie steppique dans le souss (Maroc). Ecologia Mediterranea, 9 (1): 77-88.
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