Mediterranean gypsum scrub

Open scrub on gypsum-rich substrata growing in dry to semiarid Mediterranean climate, mostly distributed in the central and south-eastern Iberian Peninsula and with small representations in some Mediterranean islands (Sicily and Cyprus). It develops on sedimentary evaporitic bedrocks rich in gypsum (gypsisols in the FAO soil classification), locally called aljezares (from Arabic aljez = gypsum) of Triassic, Oligocene and Miocene ages. Many of the species of this type are linked to this particular edaphic conditions, being called gypsohytes or gypsophilous species. Many of them are narrow endemics of Iberian or even more restricted distribution, particularly among the scrub species, but also some of the annuals. A few of them are also present in North Africa (Helianthemum squamatum, Lepidium subulatum, Ononis tridentata) or in other countries in the Mediterranean Europe (Chaenorhinum exile, Ctenopsis gypsicola). The richness of endemics is higher in the centre and the south of the Iberian Peninsula than in the northern part of the habitat’s range (Ebro Depression), being highest in the southeast (Almeria, Murcia and Alicante). In addition to the gypsophytes, a number of basiphilous scrub plants of wider distribution and ecology occur, such as Rosmarinus officinalis and Thymus species. Remarkably, also among the lichens, one endemic exists: Diplotomma rivas-martinezii. Other lichen species of the habitat have a wide distribution over the Middle East and Central Asian arid territories, suggesting an old connection with these areas during the desiccation of the Mediterranean Sea in the Messinian episode (Upper Miocene). The EU28 area of this type is restricted to parts of peninsular Spain where gypsum outcrops occur under severe dry climatic conditions and tiny representations in Cyprus and Sicily. It occurs also in some areas of North Africa.

The typical structure of this habitat is formed by three main elements: (1) a chamaephytic scrub of low height (5-60 cm) and low cover in a dispersed formation, (2) a hard lichen crust covering the soil in between the shrubs, and (3) an ephemeral therophytic community appearing in rainy springs, populating the space between shrubs in early summer. This state is quite stable and natural succession is slowed down because of the extreme conditions of soil, slope and severe drought. A moderate sheep grazing pressure is compatible with an optimal state for preventing succession towards shrubland (maquis with Juniperus and Quercus coccifera) and perennial grassland (Machrochloa tenacissima, Brachypodium retusum). The appearance of this habitat, humble, dry and open, entails an idea of poverty and aridity largely extended in the mentality of most of the human society. For that reason, very often those gypsum scrubs have been despised and its area used as landfills, for wind turbines, for quarrying gypsum, and other uses, even after the approval of the Habitat Directive by the European Union in which they were declared as a Priority Habitat. In addition to this and despite its importance, many attempts have been made to perform restoration of woodlands, mostly with pines (Pinus halepensis), which have mostly failed due to the severe soil and climate conditions.

Indicators of good quality:

The following characteristics may be considered as indicators of good quality, but these indicators differ in different regions:

• Presence of gypsophytes, particularly endemics, including threatened species

• Scrub of low height and low cover

• High cover of open soil covered by lichen crust

• Low to moderate cover of vascular plant vegetation, particularly chamaephytes

• Low cover of encroaching tall grasses and shrubs

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats