Coastal Cliffs of the Maltese Islands
The coastal cliffs of the Maltese Islands are characterised
by vertical or near-vertical rock faces rising from the sea to
heights of up to 70-130m above mean sea level and continuing
below it down to depths of 80m in places. Steep slopes which are
often terraced and which have been under cultivation for
hundreds of years cap parts of these cliffs whereas spectacular
boulder screes (known locally as rdum) dominate others.
Coastal rdum landscapes typically consist of an Upper Coralline
Limestone block overlying Blue Clay. Erosion and recession of the
latter causes the cliff edges to collapse under their own weight
resulting in massive boulders which then move downslope over the
mobile clay, particularly when this is wet and plastic. A boulder
scree thus results at the foot of the escarpment and, where the
rdum is close to sea level, extends downslope to the sea where it
may form a boulder shore in places. A perched aquifer is present in
the permeable Coralline Limestone, supported by the Blue Clay
formation. Seepage from this, in the form of scarp-foot springs,
results in the slopes below the rdum receiving abundant water
during the wet season and beyond.
Because of their relative inaccessibility both the vertical
cliffs rising from the sea and the rdum with their boulder screes
provide important refuges for many threatened and/or specialised
species of Maltese flora and fauna, including many endemics.
Within the cliff systems are found examples of many unusual
central Mediterranean coastal habitats, including clay slopes,
boulder screes, and rocky ledges on the cliff faces and karstic
limestone plateaux beyond the cliff edge. Gorges cut by extinct
streams interrupt the cliffs in places and where these dry valleys
(known locally as widien) open on the coast, they occasionally give
rise to saline marshlands and sandy and shingle beaches. Away from
the mouth of these valleys are found
characteristic watercourse and
spring habitats. With these habitats are associated rupestral,
steppic, garigue and maquis assemblages, as well as those of
temporary rainwater rock-pools that form on the karstic rock, and
those of watercourses and freshwater wetlands. Because of the
diversity of the terrain, mosaics of assemblages form; giving rise
to a very rich biodiversity.
The
fauna of the coastal cliffs includes some of the rarest of Maltese
animals. For example, the endemic snail Lampedusa melitensis
occupies a very precarious habitat of a few tens of square metres
on a small area of boulders on the south-west cliffs of Malta,
while two other rare, endemic snails (Lampedusa imitatrix and
Trochoidea gharlapsi) are found in just a few cliffside localities.
The cliffside vegetation is dominated by shrubs and is especially
important due to the presence of a large number of endemic plant
species, including the Maltese Rock Centaury (Palaeocyanus
crassifolius - the National Plant of Malta), the Maltese Salt Tree
(Darniella melitensis) and the Maltese Cliff-Orache (Cremnophyton
lanfrancoi). Other important cliff-side plants include species with
a restricted Mediterranean distribution, such as the Egyptian St.
John's Wort (Hypericum aegypticum), the Rock Crosswort (Crucianella
rupestris) and the Cliff Carrot (Daucus rupestris). Several of
these ecologically important shrubs often form associations that
are exclusive to the Maltese Islands.
The vegetation of the boulder screes is also interesting in that
it is often a mosaic of different vegetation types including
rupestral, garigue, maquis, watercourse and coastal elements and is
best termed an rdum assemblage.
The coastal cliffs, especially particularly inaccessible areas,
are also important bird-breeding sites, often supporting large
colonies of seabirds (e.g. Filfla, Ta' Cenc and L-Irdum tal-Madonna)
some of which are important on a Mediterranean scale. The Maltese
Islands are home to about 10% of the total world population of the
Yelkouan Shearwater (Puffinus yelkouan) with the Rdum tal-Madonna
supporting a third of that percentage.
The
coastal cliffs are also important from a geological and
geomorphological point of view. One particular feature of regional
importance is the Upper Coralline Limestone outlier (an outcrop of
rock occurring in a detached location from the main body of similar
rock), located in the Ghar Lapsi-Mnajdra area on the southwestern
coast of mainland Malta. In the case of the Ghar Lapsi-Mnajdra
outlier, the nearest outcrop of Upper Coralline Limestone occurs
some 1km to the northwest. This outlier is, apart from Filfla
islet, the only part of the extensive central Mediterranean
Pantelleria Rift system that is currently exposed above sea level
and as such it provides a unique opportunity for study of the
syntectonic depositional processes associated with rift
development. Additionally, the younger parts of the deposit record
a Late Miocene emergence of the Maltese Islands better than that
seen in any other Maltese locality. Some cliff faces are also the
only sites that exhibit all the local lithostratigraphical
sequence.
Geomorphologically, the Maltese coastal cliffs present a
magnificent complex of coastal land-forms including massive
limestone faces rising from depths of around 100m below sea-level
to a maximum height of 150m above; raised/submerged shore platforms
incorporating emergent and submerged sea-caves, natural tunnels and
slicken-sided faults, escarpments, boulder screes, shoreline
platforms extending offshore into shoals, arches, stacks and
blowholes.
Some areas are also of palaeontological importance. Features
include the transitional strata between the Lower Coralline
Limestone and the overlying Lower Globigerina Limestone formation,
in which beds are found especially numerous remains of the echinoid
Scutella subrotunda; the phosphate nodule beds and hardgrounds that
separate the various Globigerina Limestone members, and Quaternary
deposits which are relatively abundant in some cliff areas.
The landscape of coastal cliffs has also evolved over the years
with several types of human uses or adaptations. These include
troglodytic dwellings, agricultural terracing of unknown antiquity
and their associated dry stone walling, salt pan construction,
archaeological sites such as Bronze-Age villages, megalithic
temples, tombs and other such features, and even relict landscapes
where cliff-side agriculture and other activities have been
abandoned, and where the natural vegetation is regenerating. This
superimposition of natural and cultural elements make these coastal
cliffs even more important as they illustrate the evolution of
Maltese society and settlements over time under the influence of
the physical constraints and opportunities presented by the natural
environment, and also by successive social, economic and cultural
forces. This has resulted in a sustainable land management system,
which has not only maintained the landscape, but also helped in
supporting the biological diversity of the area.
The
coastal cliffs also assume an important role in in-situ
biodiversity conservation especially for several endemic plant and
animal species. Some of the endemic plants of the islands are
relics from the pre-glacial Mediterranean flora (these are called
palaeoendemics) and have no close relatives anywhere else in the
world. The principal palaeoendemics are Maltese Cliff-Orache (Cremnophyton
lanfrancoi), Maltese Rock-Centaury (Palaeocyanus crassifolius),
Maltese Salt-tree (Darniella melitensis), Maltese Fleabane (Chiliadenus
bocconei), Maltese Hyoseris (Hyoseris frutescens), and Maltese
Dwarf Garlic (Allium lojaconei). The genera Cremnophyton and
Palaeocyanus are monotypic, that is, represented by a single
species only, and therefore, these are also endemic to the Maltese
Islands. Palaeocyanus is most closely related to the genus
Centaurea but is more primitive than this and related genera.
Cremnophyton is related to the ancestors of Atriplex. These species
are therefore of interest from the evolutionary point of view since
they throw light on the evolution of certain important plant
groups. Other endemic plants evolved more recently, following final
separation of the Maltese Islands from the Sicilian and European
mainland (these are called neoendemics). The neoendemics include
Maltese Sea lavender (Limonium melitense), Zerapha's Sea lavender (Limonium
zeraphae), Maltese Pyramidal Orchid (Anacamptis urvilleana), and
Maltese Sea-chamomile (Anthemis urvilleana). These are closely
related to mainland species but differ due to their reproductive
isolation. Such species therefore illustrate evolutionary processes
at work.
PLEASE NOTE
MOST SPECIES MENTIONED ON THIS PAGE ARE ANIMAL AND PLANT SPECIES OF
NATIONAL OR COMMUNITY INTEREST IN NEED OF STRICT PROTECTION.
Legal Notice 311 of 2006 - Flora, Fauna and Natural Habitats
Protection Regulations, 2006 refers
