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Terrestrial Habitats

Habitats that form part of the process of succession

Specialised habitat types
  • Coastal
    Coastal specialised habitats are now extremely rare in the Maltese Islands, and the few localities supporting such habitats are under pressure as a result of human interference. Nonetheless, these habitat types still harbour important taxa.
  • Freshwater
  • Rupestral


The Process of Succession

Ecosystems undergo ecological succession, which refers to the natural process of change over time brought about by progressive replacement of one plant (or animal) community with another in response to changes in environmental conditions. This process starts off with the pioneer community and eventually leads to the development of a stable mature community, referred to as the climax community. The process of succession can halt in a pre-climax stage when some factor is limiting, such as when the organism needed to bring about the necessary changes that lead to the creation of the following community, is absent. Limiting factors may also be abiotic (non-living), such as lack of water.  

Succession can be of two types. Primary succession begins with the colonisation, by pioneer species (such as mosses and lichens) of barren substrate (rock, sand or soil), which has never supported any vegetation. On the other hand, secondary succession occurs in areas where natural vegetation has been disturbed or destroyed. The latter type is generally less species rich. 

Natural habitats in the Maltese Islands appear in different stages of ecological succession. In certain localities it is easy to differentiate between the different stages, though in other cases, the habitats occur as a mosaic of the different stages of ecological succession. There are four principle stages of ecological succession in the Maltese Islands. These are, steppe (Maltese: Steppa); garrigue (Maltese: Xagħri); maquis (Maltese: Makkja) and woodland (Maltese: Masġar). Succession is most commonly secondary.
 


Steppe (Maltese: Steppa)

Steppe is considered as the first stage in the ecological succession process. Steppe is derived from maquis and garrigue as a result of some form of degradation such as fire and grazing.

The widespread steppe is characterised by herbaceous plants especially grasses; umbellifers such as the Fennel (Scientific: Foeniculum vulgare; Maltese: Bużbież), the Giant Fennel (Scientific: Ferula communis, Maltese: Ferla) and the Wild Carrot (Scientific: Daucus carota; Maltese: Zunnarija Salvaġġa); legumes such as the Common Vetch (Scientific: Vicia sativa; Maltese: Ġilbiena Sewda); and tuberous or bulbous species like the Southern Star of Bethlehem (Scientific: Ornithogalum narbonense; Maltese: Ħalib it-Tajr Żgħir).

This habitat type is devoid of trees and mainly comprises annuals, that is, plants that live up to one year. During the dry season, this habitat type appears dry and impoverished because most plant species will, at the time, exist in the form of seeds. On the contrary, the wet season results in steppe being covered entirely by many different herbaceous plants.

Other types of steppe are encountered locally, including some natural ones formed through climatic factors. These include the rocky steppe and the clay slope steppe.

The steppes in a degraded state are more characterised by the Common Awn-grass (Scientific: Stipa capensis; Maltese: Nixxief ta' l-Isteppa) and thistles, such as the Clustered Carline Thistle (Scientific: Carlina involucrata; Maltese: Sajtun) and the Mediterranean Thistle (Scientific: Galactites tomentosa; Maltese: Xewk abjad). Geophytes, such as the Asphodel (Scientific: Asphodelus aestivus; Maltese: Berwieq) and the Seaside Squill (Scientific: Urginea maritima; Maltese: Għansar), are also encountered. Other forms of steppic communities may develop on abandoned agricultural land.


Garrigue (Maltese: Xagħri)

The second stage in the ecological succession is the garrigue. This is the most common natural vegetation type present in Malta and is characterised by low-lying, usually aromatic and spiny woody shrubs that are resistant to drought and exposure. The garrigue is characteristic of the karstic rocky regions of the Islands on outcrops of Coralline limestone. Many sub-types of garrigue exist, including the Mediterranean Thyme (Scientific: Thymus capitatus; Maltese: Sagħtar), the Mediterranean Heath (Scientific: Erica mutliflora; Maltese: Leħjet ix-Xiħ), the endemic Maltese Spurge (Scientific: Euphorbia melitensis; Maltese: Tengħud tax-Xagħri), the endemic Maltese Fleabane (Scientific: Chiliadenus bocconei; Maltese: Tulliera ta' Malta) and many others. On the other hand, maritime garigue, present on gently sloping rocky areas, is characterised by the Golden Samphire (Scientific: Inula crithmoides; Maltese: Xorbett), the Sea Samphire (Scientific: Crithmum maritimum; Maltese: Bużbież il-Baħar) and the endemic Maltese Sea Lavender (Scientific: Limonium melitensis; Maltese: Limonju ta' Malta).

Many endemic and rare species thrive in garrigue habitat, such as the Maltese Spider Orchid (Scientific: Ophrys melitensis) and the endemic Maltese Shrew (Scientific: Crocidura sicula calypso; Maltese: Ġurdien ta' Ħalqu Twil ta' Għawdex).

It is useful to distinguish between high and low garrigues since there are marked structural differences between the two. Low garrigues are characterised by low-growing bushes (less that 0.5m high), while large bushes of up to 1m in height dominate in high garrigues. Anthyllis garrigue, that is, garrigue dominated by the Shrubby Kidney Vetch (Scientific: Anthyllis hermanniae; Maltese: Ħatba Sewda) can occur as both low and high varieties, while an important type of high garrigue is that dominated by the Tree spurge (Scientific: Euphorbia dendroides; Maltese: Tengħud tas-Siġra) , which normally occurs on steep rocky ground.
 
GarrigueWithEuphorbia-2  Anthyllis_hermanniae-2

Maquis (Maltese: Makkja)

Maquis is the stage following that of garrigue in the ecological succession, and consists mostly of an evergreen shrub community, where shrubs reach a height ranging from 1-3m Frequently, this is the climax stage.

Local maquis is characterised by small trees and large shrubs such as the Carob (Scientific: Ceratonia siliqua; Maltese: Ħarruba), the Olive (Scientific: Olea europaea; Maltese: Żebbuġa), the Lentisk (Scientific: Pistacia lentiscus; Maltese: Deru), the Wild Fig (Scientific: Ficus carica; Maltese: Siġra tat-Tin), the Wild Almond (Scientific: Amygdalus communis; Maltese: Siġra tal-Lewż), as well as the Bay Laurel (Scientific: Laurus nobilis; Maltese: Randa). In order to be able to support such trees, there must be enough water and soil depth for the maquis to develop. Maquis occurs in a semi-natural state at the sides of steep valleys and rdum, which are inaccessible to man. Various subtypes of maquis occur, some of which, such as those based upon the Myrtle (Scientific: Myrtus communis; Maltese: Riħan), and the National Tree of Malta, the Sandarac Gum Tree (Scientific: Tetraclinis articulata; Maltese: Siġra ta' l-Għargħar), are very rare and threatened.

This habitat type is also rich in plants namely climbers including the Ivy (Scientific: Hedera helix; Maltese: Liedna), the Common Smilax (Scientific: Smilax aspera; Maltese: Pajżana), the Spiny Asparagus (Scientific: Asparagus aphyllus; Maltese: Sprag Xewwieki) and the Wild Madder (Scientific: Rubia peregrina; Maltese: Robbja Salvaġġa), as well as large herbaceous species like the Bear's Breeches (Scientific: Acanthus mollis; Maltese: Ħannewija) and the Italian Lords-and-Ladies (Scientific: Arum italicum; Maltese: Garni).


Tetraclinis_articulata-1  Laurus_nobilis-1

Woodland (Maltese: Masġar)

Mediterranean woodlands are characterised by sclerophyllous (hard-leaved, evergreen) trees with an undergrowth of smaller shrubs. This is the highest type of vegetation that can develop in the Mediterranean climatic regime, in other words, the climax of the ecological succession, which develops from maquis in the absence of disturbance caused by man.

In Malta this habitat was virtually exterminated following colonisation by man on the islands and grazing effects of introduced sheep and goats. Nowadays, only a few remnants are found in few areas with small copses of the Holm Oak at il-Ballut tal-Wardija, il-Ballut ta' l-Imġiebaħ, Ta' Baldu/Wied Ħażrun, and Il-Bosk near Buskett. Remnants are dominated by the Holm Oak (Scientific: Quercus ilex; Maltese: Balluta) and the Aleppo Pine (Scientific: Pinus halepensis; Maltese: Żnuber). Some of the Holm Oaks are estimated to be 500 to 900 years old. Coastal wood remnants are instead characterised by Tamarisk trees (Scientific: Tamarix spp.; Maltese: Bruk) and Chaste trees (Scientific: Vitex agnus-castus; Maltese: Siġra tal-Virgi), whereas Riparian woodland relicts are typified by the White Poplar (Scientific: Populus alba; Maltese: Luqa) and different Elm trees (Scientific: Ulmus spp.; Maltese: Speċi ta' Ulmu).

Buskett, located in the western-southwestern coast of Malta, is a semi-natural woodland, where trees namely the Aleppo Pine, together with the Evergreen Oak, the Olive and the Carob regenerate naturally. It is important for many wood-associated species, including invertebrates, mycoflora, and birds.

Tamarix_africana-2   Ulmus_minor-1

Saline Marshlands (Maltese: Bwar Salmastri)

Saline marshlands  are transitional areas that form at the interface between the marine, freshwater and terrestrial environments. Saline marshlands are dynamic systems and undergo annual cycles of changes in salinity. The salt content changes depending on rainfall, whereby in winter the saline content is low due to a diluting effect of the rain, whereas in summer, the salt content is more concentrated as water levels drop. Salinity in the salt marsh also depends on how close this is to sea and the influx of seawater into the system.

During winter, the Maltese coastal marshes are characterised by a muddy substratum on which a pool of brackish water is collected. Plants found in this habitat type must withstand changes in salinity and therefore have adapted to such conditions, by adopting special structural and physiological features. For instance, certain plants such as the Golden Samphire (Scientific: Inula crithmoides; Maltese: Xorbett) have fleshy leaves where they can store freshwater. Others, such as the Shrubby Glasswort (Scientific: Arthrocnemum macrostachyum; Maltese: Almeridja tal-Blat) and the Twiggy Glasswort (Scientific: Salicornia ramosissima; Maltese: Almeridja), have very small fleshy leaves that envelop the stem, in order to prevent the loss of water. Such plants appear to be made up of segments. Tamarisk species, on the other hand, are able to concentrate salt in their leaves, so as to eliminate the salt when the leaves are shed.

Vegetation patterns are observed in saline marshlands reflecting differences in chemical and physical conditions. Areas that remain dry or moist harbour those plants that are not aquatic such as the Smooth-leaved Saltwort (Scientific: Salsola soda; Maltese: Ħaxixa ta' l-Irmied). Shallow parts of the salt marsh that hold a small volume of water for several days, are colonized by plants that although not aquatic are still able to withstand short periods of inundation until the water dries up or evaporates. Deeper areas that remain filled with water for longer periods only support aquatic and semi-aquatic plants. Plants characteristic of saline marshlands are the Sharp Rush (Scientific: Juncus acutus; Maltese: Simar Niggież), the Sea Rush (Scientific: Juncus maritimus; Maltese: Simar tal-Baħar) and the Common Reed (Scientific: Phragmites australis; Maltese: Qasbet ir-Riħ).

Some coastal wetlands appear to be transitional between freshwater wetlands and saline marshlands in the sense that the biotic assemblages they support consist of species typical of both freshwater and saline habitats. Such wetlands have been termed 'transitional coastal wetlands'. Such wetlands arise when rainwater collects in depressions close to the sea, such as at Għadira s-Safra.

BallutTaMarsaxlokk  Juncus_acutus-1

Rainwater Rockpools (Maltese: L-Għadajjar ta’ l-Ilma Ħelu)

The movement or flow of acidified water derived from precipitation and runoff, leads to the gradual erosion of limestone substratum and the eventual formation of hollows or kamenitzas. The latter collect rainwater in winter, forming shallow freshwater rock pools, which provide a suitable habitat for a number of rare species. Freshwater rock pools are ephemeral, that is, last for only a short period, because in summer these dry up completely and may become colonised by terrestrial vegetation. Therefore, the ecological cycle of this habitat spans over a year and is divided into two stages; the wet stage occurs in winter when the kamenitzas become filled with rainwater, and the dry stage occurs in summer, when the kamenitzas remain dry. Species that are specialised to this habitat type, remain dormant in the soil during the dry stage, and emerge during the wet stage. Other species move out of the rock pool, when this is in the dry state, and return when conditions become favourable.

Plants and algae that inhabit freshwater rock pools include the Maltese Waterwort (Scientific: Elatine gussonei; Maltese: l-Elatine) and the Maltese Horned-pondweed (Scientific: Zanichellia melitensis; Maltese: Ħarira ta' l-Ilma). The duration of how long the rock pool remains with water determines the species richness of that particular rock pool. Several aquatic insects are also found in this habitat type and namely include microcrustaceans, such as the Common Copepod (Scientific: Cyclops vulgaris; Maltese: Kopepodu ta' l-Għadajjar), freshwater shrimps such as the Fairy Shrimp (Scientific: Branchipus schaefferi; Maltese: Gamblu ta' l-Għadajjar) and the Water Flea (Scientific: Daphnia pulicaria; Maltese: Żagħrun tal-Ġwiebi). Certain microorganisms that occur in this habitat are extremely rare such as the Tadpole Shrimp (Scientific: Triops cancriformis; Maltese: Gamblu ta' l-Elmu).

 
Rockpool-4  Rockpool-3

Sand Dunes (Maltese: Għaram tar-Ramel)

Sand dunes are dynamic systems that form by a slow process of accretion, that is, the build up of sand as a result of natural wave action. Sandy beaches are backed by dune systems, which provide an essential role in the stability, as well as defence of coastal communities. The formation of sand dunes depends on the sand being carried by the wind inland from the beach. Sand is deposited and trapped upon encountering clumps of vegetation or some other form of obstacle.

Dune vegetation is adapted to the harsh conditions present in this habitat. Such conditions include high temperatures, dryness, occasional inundation by seawater and accumulation of sand. Plant adaptations include extensive root systems that provide efficient anchorage in the porous and mobile substrate; and other distinctive morphological features, such as fleshy leaves to limit water loss, and the presence of short white hairs to help in temperature regulation.

Vegetation type changes across the dune system with distance from the beach, forming a typical zonation pattern. Maltese dunes in the present day may be described according to the following zonation pattern.

The most seaward zones of the dune is called the embryo dune  where perennial plants are first encountered, such as the Sea Rocket (Scientific: Cakile maritima; Maltese: Kromb il-Baħar), which pioneers the dune enabling the establishment of other plants. This species is also encountered on the drift line of the beach, that is, the highest extreme that waves reach leaving a line of organic debris. Other plants found colonising the embryo dune are the Sand Dropwort (Scientific: Sporobolus pungens) and the Prickly Saltwort (Scientific: Salsola kali; Maltese: Ħaxixa ta' l-Irmied Xewwikija). Behind the embryo dune lies the mobile dune, which is characterised by a low dune that is sparsely vegetated by plants such as the Sand Couch Grass (Scientific: Elytrigia juncea; Maltese: Sikrana tar-Ramel)  and the Sea Holly (Scientific: Eryngium maritimum; Maltese: Xewk ir-Ramel). The latter zone is followed by the semi-consolidated dune, which is characterised by the Carnation Spurge (Scientific: Euphorbia terracina), the Sea Daffodil (Scientific: Pancratium maritimum; Maltese: Pankrazju tal-Baħar) and the Sea Fennel (Scientific: Echinophora spinosa). Next lies the fixed dune, which is vegetated with a dense thicket of salt-tolerant shrubs, such as the Grey Birdsfoot Trefoil (Scientific: Lotus cytisoides; Maltese: Għantux tal-Blat) and the Southern Scabious (Scientific: Scabiosa maritima; Maltese: Skabjoża).

Maltese sand dunes also have characteristic invertebrate fauna namely nematodes (roundworms), annelids (segmented worms), several insects, amphipods (shrimp-like crustaceans) and isopods (sessile eyes crustaceans).

Over the years, many sand dunes have been lost and nowadays this habitat types is extremely restricted in the Maltese Islands. Presently there are only few that still persist and are amongst the rarest and most threatened of local ecosystems.

SandDune_3   Eryngium_maritimum-1

Valley Watercourses (Maltese: Il-Widien)

Valley watercourses  are one of the most species-rich habitats on a national scale. Yet, they are considered as one of the most endangered habitats in the Maltese Islands.

The biotic (living) communities of valleys can be divided into two groups: those growing on valley sides and those growing along the watercourse.

In gently sloping valleys, the watercourse community is similar to that of the valley sides, whereas in steep-sided valleys there is a clear distinction between communities along the watercourse and those vegetating valley-sides. Where the terrain permits, the valley sides are terraced and cultivated. The construction of man-made dams in certain valley systems has intentionally retarded the water flow for irrigation purposes. Such dams have created new freshwater habitats where a variety of aquatic and semi-aquatic species thrive.

The watercourse community is by nature dynamic and its integrity depends on the amount and frequency of rainfall as well as other abiotic factors such as the rate of siltation. Valleys are dry for some months of the year and water only flows during the wet season. However, some local valleys drain springs originating from the perched aquifers and retain some surface water even during the dry season.

In general, the greater part of local plant and animal species reliant of water during some part of their life cycle are found in valley watercourses. Various annual and perennial plants colonise the watercourse, some of which are rare on a national scale because of the restricted distribution of their habitat. An example is the very rare perennial Willow-leaved Knotgrass (Scientific: Persicaria salicifolia; Maltese: Persikarja tal-Baħrija).

Plants that grow in watercourses include herbaceous perennials such as the Water Plantain (Scientific: Alisma plantago-aquatica; Maltese: Biżbula ta' l-Ilma) and the Water Speedwell (Scientific: Veronica anagallis-aquatica; Maltese: Veronika ta' l-Ilma). Perennials, unlike annual plants, are able to withstand periods of dryness. Watercourse plants require a good underground system of roots or rhizomes for anchorage to the unstable waterlogged substrate of watercourses. Attached watercourse vegetation mainly comprises grasses, sedges and rushes, while algae thrive in the open water, like species of Spirogyra and Zygnema. One of the most common plants to colonise valleys is the Giant Reed (Scientific: Arundo donax; Maltese: Qasba Kbira). Encroachment by this reed results in reduction of water current, however when the water passes through the rhizomes of this plant, the water is filtered from nutrients. The Giant Reed is often replaced by the Common Reed (Scientific: Phragmites australis; Maltese: Qasbet ir-Riħ) at the mouth of valley watercourses where freshwater feeds into the sea.

Remnants of riparian woodlands, located on the bank of a watercourse, still exist along a few watercourses where water flow is abundant. Examples of trees growing along watercourses include the rare White Poplar (Scientific: Populus alba; Maltese: Siġra tal-Luq), the Mediterranean Willow (Scientific: Salix pedicellata; Maltese: Żafżafa ż-Żgħira) and the Grey-leaved Elm (Scientific: Ulmus canescens; Maltese: Siġra tan-Nemus). Different subtypes occur in different localities.

Watercourses provide habitat and food to various animals, the most well known being the only amphibian found in Malta, the Painted Frog (Scientific: Discoglossus pictus pictus; Maltese: Żrinġ), and the legally protected endemic Maltese Freshwater Crab (Scientific: Potamon fluviatile lanfrancoi; Maltese: Qabru). A huge variety of insect and other invertebrate fauna also thrive in local valleys, such as dragonflies and damselflies, semi-aquatic grasshoppers, mayflies, aquatic and semi-aquatic beetles, such as the Large Predacious Diving Beetle (Scientific: Dysticus circumflexus; Maltese: Wirdiena ta' l-Ilma), water-associating flies, bees and wasps, small crustaceans and many others. Some of these are only found in these habitats and some are only known from one or a few localities in the Maltese Islands.

Watercourse-2  Salix_pedicellata-1

Caves (Maltese: Għerien)

In spite of the calcareous nature of Malta's rocks, deep caves are not frequent. Maltese caves are inhabited by organisms, which are adapted to live in such habitats and therefore, have a very restricted distribution. The best-known cave dwellers are bats but there are many other species, particularly invertebrates. Moreover, a number of these species are endemic to the Maltese Islands and therefore, of great scientific interest.


Cliffs and Boulder Shores (Maltese: L-Irdumijiet u l-Komunitajjiet Rupestrali)

Cliffs  found mainly along southern and western shores of Malta, Gozo and Comino, represent an important natural habitat because they harbour many interesting species of flora and fauna including endemic forms.

Rupestral plant communities mainly consist of halophytic shrubs and also comprise endemic species that are restricted only to this habitat, such as the Maltese Cliff-orache (Scientific: Cremnophyton lanfrancoi; Maltese: Bjanka ta' l-Irdum) and the National Plant of Malta, the Maltese Rock Centaury (Scientific: Palaeocyanus crassifolius; Maltese: Widnet il-Baħar), both belonging to monospecific genera. The cliffs in Gozo, support rupestral species that are not present in Malta, namely the Gozo Hyoseris (Scientific: Hyoseris frutescens; Maltese: Żigland ta' Għawdex) and the Maltese Everlasting (Scientific: Helichrysum melitense; Maltese: Sempreviva ta' Għawdex). Plants found on cliffs need to be resilient to the harsh abiotic conditions such as lack of water, strong winds, sea spray and little soil. Nonetheless, the inaccessibility of cliffs has meant that they have received little relative interference by man.

Cliffs provide shelter and breeding habitat for many bird species, such as the Cory's Shearwater (Scientific: Calonectris diomedea; Maltese: Ċiefa), the Mediterranean Shearwater (Scientific: Puffinus yelkouan; Maltese: Garnija) and the Maltese National bird, the Blue Rock Thrush (Scientific: Monticola solitarius; Maltese: Merill) .

The South Western Cliffs of mainland Malta provide a vital habitat to one of the rarest animals in the Maltese Islands, the Maltese Door Snail (Scientific: Lampedusa melitensis; Maltese: Dussies ta' l-Irdum). Other rare endemic snails also have their distribution restricted to only a few cliff-side localities, such as the Filfola Door Snail (Scientific: Lampedusa imitatrix gattoi; Maltese: Dussies ta' Filfla) and the Għar Lapsi Top Snail (Scientific: Trochoidea ghar lapsi; Maltese: Żugraga ta' l-Irdum).

Palaeocyanus_crassifolius-1  Cliffs-1