Flora and plant communities of South-Western Morocco

The site presents the vascular plants of south-west Morocco, where a considerable number of missions have been carried out since 1971, first for a thesis (Jean-Paul Peltier, 1982) and then to supervise research work (Ahmed El Aboudi, 1990 and 2000; Fouad Msanda, 1993 and 2004). For more information about the territory concerned, see the section entitled "Geographical divisions of Morocco". Teline also has photos of taxa, which are often endemic plants, from other phytogeographic regions in Morocco, sent in by various contributors.

The south-west of Morocco is considered to be an area of refuge within the Mediterranean hotspot. This geographical area, in which a variety of phytogeographic elements can be found, is something of a biogeographic crossroads with exceptional diversity in terms of species, individuals and environments. More particularly, the region is unusual because of the presence of plant lines that go back to the Tertiary period, requiring high temperatures (megatherm species), due to the region's particularly favourable climatic conditions.

The current species of tropical origin are especially drought-resistant ones, represented by a few trees, the argan, the gommier marocain (Acacia gummifera Willd.), the dragon tree and also by cactoid and succulent species: Euphorbia, Kleinia, Aeonium, Periploca, Drusa, Andrachne, Kalanchoe, Apteranthes, Orbea, Astydamia, Warionia, etc.

The succulent plants are reminiscent of the landscapes of the Canary Islands, which explains why the area where the argan tree grows in Morocco was long known as "macaronesian". In reality, the sector belongs to the North African-Mediterranean region (Medail & Quezel, 1999).

Only Laurus azorica (the Azores Laural), which has no more than a relict population in the jebels of Imzi and Adad Medni in the Kerdous, is regarded as a mesophilic megatherm species. Its status as a species is currently being questioned, because recent data suggest that there is only a single species of Laurus: Laurus nobilis (Rodriguez-Sanchez et al., 2009).

The sector also has many endemic species, almost all of which belong to Mediterranean plant lines. For example, six of the thirty-two endemic genera found in the Maghreb grow there: Hesperolaburnum, Sclerosciadium, Hannonia, Traganopsis, Argania and Trachystoma.

The most recent studies on Sapotaceae (Swenson & Anderberg, 2005; Smedmark et al., 2006; Smedmark & Anderberg, 2007) indicate that the argan is a sister group of Sideroxylon mascatense, found from the Horn of Africa (Ethiopia) to south-west Asia (Pakistan). This means that the argan is of East African origin and that it migrated westwards during the Paleogene period. The authors also suggest reverting to the name Sideroxylon spinosa.

The history of the argan tree begins to be better known: the ancestor was widespread distributed across North Africa in the mid-Miocene and the age of divergence shows that the descendants begin to individualize towards 17 MA in relation to the increasing aridification of the Africa (Mairal et al., 2017). Its origin, however, is more tricky, due to the absence of the argan fossil remains.

The argan [Argania spinosa (L. ) Skeels] is the region's most important tree. It is the only example of the Sapotaceae family found in Morocco and is used for forestry, fruit and fodder, making it the mainstay of a traditional agrarian system, while also playing an irreplaceable role in the ecological balance of the region.

Arganeraie forests currently cover an area of approximately 800,000 hectares. They are mainly found in the south-west of Morocco, along the Atlantic seaboard, from the mouth of the River Tensift in the north, to the mouth of the Draa River in the south. The argan also grows in the plain of the Sous, on the southern slopes of the western High Atlas and on the northern and southern slopes of the western Anti-Atlas up to altitudes of 1,300-1,500 m. Two small stands have been reported in the high valley of the Grou River south-east of Rabat and in the north-western foothills of the Beni-Snassen, near Oujda. It would seem that these two extremely isolated stands are the result of a fairly recent dispersion, probably by man. Lastly, in the Sahara, the argan extends as far as the Hamada of Tindouf, where it finds the water it needs along the banks of the wadis.

The argan is a heat-loving and drought-resistant tree, requiring anything from an arid, hot and temperate bioclimate (along the coastline and in the plains), to a semi-arid, hot and temperate bioclimate (slopes of the High Atlas and the Anti-Atlas foothills), or even Saharan conditions, further south. Annual rainfall is between 250 and 400 mm from Safi to Agadir. From the plain of the Sous River to the Anti-Atlas, the annual rainfall varies from 250 to 150 mm. Further south, in desert areas, it is often significantly lower than 100 mm. Under these conditions, the argan is only found along temporary water courses, where it uses the runoff waters.

For the last few decades, desertification has been the region's main environmental problem. To halt and reverse the increasing degradation of the argan population, a number of projects have been planned or carried out. All are intended to bring economic benefits at the local level. The main challenge is to build a management model that defines the shared objectives of all the social stakeholders.

The scientific nomenclature is borrowed from the most recent studies: the best-known synonyms are also given.

The scientific names of the families are those selected by the Angiosperm Phylogeny Group (APG IV, 2016: An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: Botanical Journal of the Linnean Society. Paper complied by James W. Byng et al.

Certain photos bear comments on taxonomy, ecology or biogeography.

The purpose of this site is simply to spread awareness of the plant species of the region - including many endemic species of great heritage value - before human activities lead to their complete disappearance.

Jean-Paul Peltier

Last modified on February 5, 2018 at 9:52:23 AM GMT.