Sea cliffs and rocky coastlines 7

I TA L I A N H A B I TAT S
Sea cliffs and rocky coastlines
7
Italian habitats
Italian Ministry of the Environment and Territory Protection / Ministero dell’Ambiente e della Tutela del Territorio
Friuli Museum of Natural History / Museo Friulano di Storia Naturale · Comune di Udine
I TA L I A N H A B I TAT S
Scientific coordinators
Alessandro Minelli · Sandro Ruffo · Fabio Stoch
Editorial committee
Aldo Cosentino · Alessandro La Posta · Carlo Morandini · Giuseppe Muscio
"Sea cliffs and rocky coastlines · Life between cliffs and saltiness"
edited by Alessandro Minelli
Texts
Carlo Nike Bianchi · Ferdinando Boero · Luigi Carobene · Giuseppe Carpaneto · Simonetta Fraschetti ·
Carla Morri · Simonetta Peccenini · Margherita Solari
English translation
Elena Calandruccio · Gabriel Walton
Illustrations
Roberto Zanella
Graphic design
Furio Colman
Photographs
Archive of Circolo Speleologico e Idrologico Friulano 83, 138 · Archive of Unione Speleologica Bolognese
(photo: E. Altara) 102 · Roberto Argano 73 · Claudio Aristarchi 33, 35/3, 37/2, 40/1, 43, 46, 49, 53, 58/3 ·
Mauro Arzillo 91, 94, 97, 98, 101/2 · Paolo Audisio 71, 146 · Flavio Bacchia 104, 115, 124, 126, 132/2,
149 · Pietro Baccino 34, 35/1, 37/1, 37/3, 38/1, 38/3, 39/3, 40/2, 40/3, 44/1, 44/2, 45/1, 45/2, 47/1, 48/1,
48/3, 48/4, 50, 62, 67/2 · Giuseppina Barberis 41/2, 47/2, 58/1, 58/2 · Enrico Benussi 84, 85 ·
Carlo Nike Bianchi and Carla Morri 109, 111, 112, 116, 118, 119/1, 119/2, 119/3, 120/1, 120/2, 120/3,
121, 123, 125, 130/1, 130/4, 132/1, 133/1 · Ferdinando Boero and Simonetta Fraschetti 106, 113, 117,
119/4, 120/4, 127, 128, 130/2, 130/3, 132/3, 132/4, 133/2 · Eugenio Busetto 59, 63, 64, 65 ·
Luigi Carobene 7,10, 11/1, 11/2, 12, 27, 28, 29, 69, 108, 141 · Giuseppe Carpaneto 79, 80, 81 ·
Fabio Conti (Archive of Centro Ricerche Floristiche dell’Appennino) 35/2, 48/6 · Adalberto D’Andrea 30, 54 ·
Domingo D’Avenia 42 · Paolo Fabbro 68, 147 · Tiziano Fiorenza 78, 87, 93, 96 · Gianluca Governatori 60 ·
Luca Lapini 82, 86, 101/1 · Daniele Macale 88, 89/1 · Ugo Mellone 6, 9, 22, 32, 137, 142, 144, 145 ·
Luigi Minuto 41/1· Giuseppe Muscio 20, 75/2, 134, 148 · Francesco Orsino 36, 45/3, 48/2, 51, 67/1 ·
Paolo Paolucci 100/2, 101/1 · Roberto Parodi 90, 99 · Simonetta Peccenini 52 · Paola Sergo 136 ·
Daniela Tinti (Archive of Centro Ricerche Floristiche dell’Appennino) 38/2, 39/1, 39/2, 47/3, 48/5, 56, 57, 66 ·
Paolo Utmar 70 · Augusto Vigna Taglianti 72, 75/1, 76, 77/1, 77/2, 77/3, 89/2, 92, 95
Sea cliffs and rocky coastlines
Life between cliffs and saltiness
©2004 Museo Friulano di Storia Naturale, Udine, Italy
All rights reserved.
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form, or
by any means, without the prior permission in writing of the publishers.
ISBN 88 88192 15 8
ISSN 1724-6539
Cover photo: vertical layers of sandstone, path to Cinque Terre, Liguria (photo by L. Carobene)
M I N I S T E R O D E L L’ A M B I E N T E E D E L L A T U T E L A D E L T E R R I T O R I O
M U S E O F R I U L A N O D I S T O R I A N AT U R A L E · C O M U N E D I U D I N E
Italian habitats
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Carlo Nike Bianchi · Ferdinando Boero · Luigi Carobene · Giuseppe Carpaneto ·
Simonetta Fraschetti · Carla Morri · Simonetta Peccenini
Morphology, processes and dynamics. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Luigi Carobene
1
Caves and
karstic
phenomena
2
Springs and
spring
watercourses
3
Woodlands
of the Po
Plain
4
Sand dunes
and beaches
5
Mountain
streams
Terrestrial flora and vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Simonetta Peccenini
Terrestrial fauna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Giuseppe Carpaneto
Submerged communities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Carlo Nike Bianchi · Ferdinando Boero · Simonetta Fraschetti · Carla Morri
6
The
Mediterranean
maquis
7
Sea cliffs and
rocky
coastlines
8
Brackish
coastal lakes
9
Mountain
peat bogs
10
Realms of
snow and ice
Conservation and management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Carlo Nike Bianchi · Ferdinando Boero · Luigi Carobene · Giuseppe Carpaneto ·
Simonetta Fraschetti · Carla Morri · Simonetta Peccenini
Suggestions for teaching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Margherita Solari
Select bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
11
Pools,
ponds and
marshland
12
Arid
meadows
13
Rocky slopes
and screes
14
High-altitude
lakes
15
Beech
forests of the
Apennines
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Index of species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Introduction
C. NIKE BIANCHI · FERDINANDO BOERO · LUIGI CAROBENE · GIUSEPPE CARPANETO ·
SIMONETTA FRASCHETTI · CARLA MORRI · SIMONETTA PECCENINI
A coastline more than 7450 km long
surrounds Italy, the Mediterranean
outlining the familiar “boot” slanting on
the pale blue background on maps
and satellite photographs.
From Ventimiglia near France to Trieste
in the east, through the Strait of
Messina and Santa Maria di Leuca,
almost all the regions of the Italian
peninsula have coastal access, as, of
course, do its large and small islands.
Coastlines on maps usually have two
different colours, some are green and
others brown, in lighter or darker
shades. Green corresponds to low,
flat, generally sandy shores, shades of
brown identify high, usually rocky
Irregular morphology of limestone coast in
Cirella (Calabria): these sharp, spiky forms are
coasts. These two types have differing
due partly to karstism, partly to the action of
ecological, geological, historical and
sea water
economic importance.
This volume treats only rocky coastlines which, as we shall see, are very
different in both geological and vegetational terms, as well as in the use to
which humans put them.
High coastlines are produced by lengthy interactions between water masses
(here we consider only sea water) and rocky blocks (islands or continents).
Both masses move: the former undergo long-term variations in level (e.g.,
glacio-eustatic oscillations) and short-term ones (tides, swell, seiche, seaquakes); the latter may slowly slide upwards in tectonically active areas; move
occasionally (bradyseism) in volcanic areas; jerk suddenly for more than one
metre in seismic areas; or the entire coast, even its submerged part, may
slowly rise in areas of isostatic adjustment, etc. (see table “Changes in
shoreline position”, page 11).
Inlet along a rocky coast in Salento (Apulia)
7
8
These interactions underlie the morphogenesis of high coasts and also
interact with exogenous processes, independent of marine ones.
In Italy, high, rocky coastlines prevail over low, sandy or gravelly ones, and
are therefore very important in determining coastal environments. Their origin
may be traced back to the Holocene rise of the sea after the most recent
glaciation.
However, many high coasts date back to previous high sea levels during interglacial periods or, as in lowering (or submersion) coasts, to morphologies of
continental origin.
Glacio-eustatic oscillations cause marine moulding of high coasts during interglacial periods and subaerial moulding (therefore not marine) during
glaciations.
It may also be inferred that climatic variations play a fundamental role in the
creation and evolution of high rocky coasts, causing alternating marine and
continental erosion, acting in different ways.
When examining high coasts, we must always take into account that their
present condition is the product of lengthy evolution (thousands or even
hundreds of thousands of years), so that a simple correlation between visible
aspects and the processes now operating would be misleading.
High coasts often have cliffs plunging into the sea, sometimes vertically. They
may be active or inactive. The coastal dynamics giving rise to the formation of
cliffs is complex - the result of many causes which produce movements of the
Earth’s crust and water, and to the large number of processes (both marine
and subaerial) which take place. These, in turn, are influenced by a series of
factors (lithology, rock structure, local geodynamics, physical characteristics
of water, etc.), which contribute to the production of different results according
to area. It is difficult to find two high coasts with similar morphology and
biological habitats.
The main morphological situations in Italy will be described later: highgradient cliffs receding suddenly or gently; steep flanks covered with
vegetation; seabeds which may be deep, or feature large, shallow erosion
platforms; high shores protected from direct sea action by deposits of debris,
landslides, strips of beach, etc.. In each one of these are differing animal and
plant populations, both under and above water.
In subaerial environments, the steeper the cliff, the more difficult it is for plants
to colonize the area. Cliff vegetation is highly specialized, and species with
particular soil and climatic requirements are absent. Hard, submerged
seabeds, i.e., the continuation of rocky land, host the most spectacular
subterranean seascapes.
9
Rocky coastline of island of Marettimo (Sicily)
This is why most Protected Marine Areas are near high, rocky coasts. On land,
organisms attached to the substrate are almost exclusively plants,
mushrooms and lichen. But submerged rocks are covered by highly differing
animal and plant communities. The erosive action of waves is often enhanced
by perforating organisms, or may be mitigated by the protective effect of bioconstructors, organisms which create calcareous bodies. Coral limestone is
the most important product of bio-constructive phenomena along Italian
shores.
The flora and fauna which colonize these borderline environments, dominated
by lack of productive soil, high saltiness, and both sea and wind erosion, are
poor and more or less specialized. Land and sea communities are always
closely associated, and energy continually flows between these two bordering
habitats. Abiotic factors, like wind and waves, and biotic ones such as the
activity of seabirds and other organisms, provide a constant exchange of
organic matter between land and sea.
Morphology, processes and dynamics
LUIGI CAROBENE
High coastlines are treated here very simply, without any further classification,
although the topic is very complex. It is essential to bear in mind that the study
of high coasts implies analysis of coastal surfaces (flanks, cliffs, seabeds), i.e.,
erosion surfaces which developed over time as the consequence of events of
regional and global importance related to tectonics, eustatism and climate.
High coasts are therefore unstable and changeable features of the landscape,
characterized by a great variety of aspects.
Let us thus begin our study of high shores with their morphological
characteristics, their dynamic ones, which control their development, and the
evolution of cliffs over time.
CHANGES
IN
SHORELINE
POSITION
COASTAL HINTERLAND
C O A S TA L
HINTERLAND
MOVEMENTS OF THE SEA SURFACE
MOVEMENTS OF THE EARTH’S SURFACE
Fast (local scale)
earthquakes
bradysism
landslides
Slow (regional scale)
subsidence
tectonics
isostasy
High cliff on island of Palmaria (Portovenere, Liguria)
Short-term
tides
waves
storms
Long-term
eustatism
(of various kinds)
variations in geoid’s shape
SEA
11
■ Types of high coasts
12
13
High coasts have a large number of characteristics which do not depend only
on the main geological features of the formations constituting inland areas
and the climatic and meteo-marine aspects of the area, but also on many
other factors. The main morphological aspects which describe emerging
surfaces (flanks, scarps or cliffs) are: gradient, height, shape, and regularity of
surfaces.
Main emerging morphologies. High coasts may be divided into three main
morphologies: coastal flanks, flank-cliffs and cliffs.
Coastal flanks. These are sloping
COASTAL FLANK
flanks, up to hundreds of metres high,
the gradient of which is less than 45°.
They are covered with debris and the
products of weathered substrates,
and are usually carpeted with
vegetation. Although the steepness of
Processes: subaerial processes (weathering,
flanks depends on the geo-technical
erosion, etc.) affect foot of cliff more than
marine ones
characteristics of rocks, weathering is
Morphologies: high, steep flanks covered by
also very important. These shores are
debris, weathering products and vegetation
typical of tropical regions, where the
warm-humid climate contributes to intense chemical alteration. Here, powerful
weathering of rocks hinders the formation of steep cliffs, and produces large
quantities of debris which, through various means (solifluction, landslides) may
fall to the foot of the flanks, thus contrasting the erosive action of waves.
●
Flank-cliffs. Shores vary in profile,
i.e., the upper portion is called a flank
and the lower one a cliff. These two
sections are separated by clearly
different gradients.
Flanks were formed by mainly
subaerial processes of weathering
and erosion, which produced great
quantities of debris and lowered the
flank gradient after the Holocene rise
in sea level, which caused erosion of
●
High limestone cliffs, plunging into deep water, slowly retreat, mainly due to external forces; the sea’s
action at the base of the cliff is strong (Capo Caccia, Sardinia)
FLANK-CLIFF
Processes: strong subaerial processes along
flank; at cliff foot, action of sea prevails and
gives rise to platforms
Morphologies: flanks covered by debris and
vegetation; cliffs with fast-receding rock
14
the flank base. These coasts are typical of areas where periglacial activity
was intense and moulded the flanks during glaciations; later, in interglacial
periods, the flanks were covered with vegetation, and high eustatic levels
gave rise to the formation and recession of cliffs.
also due to latitude, which influences the height of waves: at high latitudes, ice
may protect shores in certain periods of the year. Generally speaking,
maximum removal of base debris occurs in temperate areas, and is minimum
in tropical and polar regions.
Cliffs. These steep rocky flanks
CLIFF
show the powerful action of the sea at
their base (drawing c, page 15). They
are subvertical, sometimes even
overhanging, rocky walls of heights
varying between a few to hundreds of
metres (e.g., lava cliffs in Tenerife).
Cliffs cut deposits of any origin, from
Processes: subaerial and marine on cliff, with
semi-incoherent (coastal deposits,
powerful sea action at foot
alluvial cones, etc.), to extremely hard,
Morphologies: rock walls at angles of more
compact rocks (granite, limestone,
than 45°, steep, subvertial, overhanging;
variable retreat, according to lithology and
etc.). This influences the velocity of
water depth
their recession but also their shape,
verticality and height. Verticality is not a constant characteristic of cliffs,
because intense exogenous action may lower their gradient. Cliffs are
therefore “free surfaces” without debris produced by weathering, but if
gradients are not too high, debris remains on the surface and vegetation may
grow.
The formation and recession of cliffs are due to the indirect action of the sea,
as waves have an effect only at the cliff base. In actual fact, the evolution of
cliffs is mainly caused by rock falls and the erosion by exogenous agents. The
recession velocity of cliffs is extremely variable, between a few millimetres to
tens of centimetres a year, but it may even exceed one metre: in the former
case, cliffs are stable and marine and subaerial processes are weak; in the
latter, cliffs are unstable, so that marine and subaerial erosive phenomena are
very severe.
The extent of erosive effects largely depends on local factors, such as the
type of rock, its structure and exposure to waves. Active cliffs owe their
condition to the ongoing capacity of waves to remove the debris
accumulating at their base.
This supply-removal balance depends on climatic variations, tectonics, and
variations in sea level. If removal is greater than supply, cliffs remain the same
and even recede; if the opposite occurs, alluvial cones are deposited and
beaches form at the base of cliffs, thus lowering their gradient. Differences are
Main submerged morphologies.
High rocky coasts occur in two typical
morphologies, cliffs and shore
platforms opposite, although along
some coasts cliffs may rise from deep
seabeds and are thus called plunging
cliffs. Shore platforms are subhorizontal surfaces entering the sea
(slope less than 3°), tens or even
hundreds of metres wide.
They have various names: shore
platforms, underwater platforms,
abrasion or erosion platforms, cut by
waves, storm platforms, etc.. Here we
use the terms “marine” or “shore”
platforms.
They are divided into Type A and Type B
platforms.
●
Type A platforms gently slope into
the sea and join the base of cliffs at
high tide level. They are formed by the
continual regression of cliffs, and their
width and gradient depend on the
velocity of shore recession and thus on
the erosion resistance of cliffs and
wave energy. These platforms may be
tens of metres deep off the coast.
●
a
MSL
h
b
MSL
h
c
MSL
h
According to geographical position,
geological composition of coastline,
and meteo-marine and climatic
characteristics, high rocky coasts have
different morphologies:
a. cliff-platforms type A
b. cliff-platforms type B
c. immerging cliffs in deep water
Type B platforms have two levels: an upper high tide level, and a lower level
under the low tide mark. The two surfaces are separated by a step a few
metres high; the high-tide surface is sub-horizontal. Although the formation of
the upper surface is mainly due to subaerial weathering, there may be other
factors at stake, such as differences in height between high and low tides.
●
15
16
1. High coasts without cliffs, protected
Processes: flanks undergoing subaerial
modelling, unstable, with falling debris at foot
- scarce removal of debris by waves
- shores protected from waves
Morphologies: landslide deposit, human
interventions (banks, roads, reclaimed land)
2. High coasts without cliffs, unprotected
Processes: evolving flanks, unstable,
subjected to landslides, with little vegetation
- removal of fallen debris by waves and
currents near shoreline
Morphologies: detrital seabeds
- possible narrow, unstable beaches
3. Active cliffs, platforms, breakers
Processes: strong waves which produce
conspicuous recession of cliffs
Interactions between subaerial and marine processes. These are divided
as follows:
High coasts without cliffs. High shores with flanks of varying steepness but
without cliffs at their base have two different aspects.
- the former type (1) is subjected to intense subaerial flank moulding. This
produces large quantities of accumulated debris at the flank base. Wave
action is unable to remove these deposits completely and, over time, beaches
of varying width develop, protecting the flanks from the direct action of the sea
and making them stable. Human interventions, such as beach defences,
protected sea fronts, etc., may produce the same effects.
- In the latter type of shore (2), debris produced by subaerial processes and
falling into the sea is completely removed by waves. The sea therefore erodes
the base and flanks become unstable and active, i.e., a dynamic balance
arises between flank evolution and removal of debris by waves and shore
currents.
●
Morphologies: unstable, subvertical cliffs and
sea platforms (shallow water)
Processes: transport and sedimentation of
debris along shores
- subaerial modelling of cliffs
High coasts with cliffs. The erosion/sedimentation balance along coasts
influences the evolution of cliffs greatly, causing various situations, the most
important of which are shown (3, 4, 5, 6).
- The first case (3) describes maximum erosion (see following paragraph),
whereby waves break because of deep seabeds, giving rise to maximum
erosion at the cliff base. This makes cliffs recede quickly, particularly if the rock
is poorly coherent and soft. Most debris is removed by waves, and abrasion
platforms and unstable, subvertical cliffs develop.
- In the second case (4), seabeds are deeper and waves do not break, but
reach the rocky cliff and are reflected. Erosion and production of debris are
reduced, and cliffs are therefore active but recede slowly, especially if their rock
is hard and compact.
- In the third case (5), the shore has large amounts of debris, produced both
by erosion of flanks and by shore current transport. Small deposits of debris
may form and give rise to narrow beaches. The cliffs are partially protected and
are only eroded by strong sea-storms, so that they recede gradually.
- In the fourth case (6), the amount of debris transported by shore currents,
rivers or flanks is such that large, stable beaches are formed, protecting the
cliffs from the force of waves. They become stable, i.e., inactive.
Morphologies: inactive cliffs
- stable beaches
- deep water
●
●
4. Slightly active cliffs, reflected waves
Processes: little erosion of cliffs
Morphologies: high, stable cliffs
- deep water
5. Protected cliffs, beaches, poor
sedimentation
Processes: limited sedimentation along coasts
- occasional erosion of cliffs
Morphologies: limited recession of cliffs
- narrow, unstable beaches
- deep water
6. Inactive cliffs, stable beaches, intense
sedimentation
High coasts with inherited morphology. Analysis of high coasts shows both
present processes and the effects they have produced in time. However, the
17
18
High coasts with continental flanks
Processes:
flanks undergo subaerial modelling
-sea action at foot
Morphologies:
these coasts often have
plunging cliffs in deep water without
littoral platforms
Sinking
coastline
High coasts with flanks of marine origin
Processes:
flanks undergo subaerial modelling
-sea action at foot
Morphologies:
old marine terraces outcropping along coast
-present receding cliffs
-formation of littoral platforms
Uprising
coastline
shapes and deposits of coastlines often have ancient causes. In this case, it is
essential to reconstruct the geological history of the region to determine the
succession of past events and gain a clear understanding of the present-day
coastal dynamics. There are many possibilities, two of which are shown in the
figure.
- Above: shores are submerged by concomitant tectonic lowering of the
coastline and a rise in sea level. Submersion coasts develop, which have
inherited flanks of continental origin (e.g., rias and coasts of Dalmatian type).
However, the two movements may be relative, not absolute. In northern
regions which were covered by ice during the most recent glaciation, the
glacio-eustatic rise in sea level (about 100-120 m) formed the well-known
fjords, which are valleys previously filled with tongues of ice. In this case, the
coasts too underwent an isostatic rise, which was, however, smaller than the
eustatic one.
- Below: the rise in the coastline is greater than the eustatic rise and therefore
coastlines have inherited flanks of marine origin. Along Italian shores, where
tectonic and isostatic processes have produced rises of about 0.5-1
mm/year, the coasts may have several tiers of marine terraces up to hundreds
of metres above the present sea level, which are now moulded by subaerial
processes.
■ Coastal processes
19
Coastal morphogenesis derives from a series of actions produced by water
masses which move for various causes and in different ways.
Analysis of waves is particularly important, as they are certainly the main
morphogenetic agent. Waves can transform energy accumulated offshore
which is sufficient to destroy high coasts, but they also carry and accumulate
rocky debris (see chart below). Only the causes which produce movements of
water are discussed here. Masses of moving water are the agents, which are
identified according to their type of movement. Moving water has kinetic
energy which is expended to carry out processes, i.e., work, which in turn
depends on the water mass and its velocity and duration in time.
Direct and indirect actions performed by agents are processes; they are
influenced by factors which modify them according to place and time,
resulting in differing effects. The erosive process is highly important in the
evolution of high coasts, and occurs in various ways (see chart below). Waves,
currents and tides produce results, i.e., the shapes and deposits which
characterize both high and low coasts.
They, in turn, are influenced by other factors, among which of particular
importance are the transgressive and regressive phenomena caused by
eustatism, and vertical movements of the coast due to tectonics, isostasy, and
diagenetic and volcanic processes.
CAUSES
pressure gradient
thermal gradient
salt gradient
gravity
earthquakes
These provide potential energy
to the system, causing enormous
masses of water to move
Moving water mass:
waves
currents
tides
tsunami
The agent may be quantitatively
described with typical parameters
AGENTS
PROCESSES
erosion
transport
sedimentation
RESULTS
Erosion:
high coasts,
sea platforms
rocks, faraglioni, arches
grooves, grottoes
corrosion forms
These produce coastal morphogenesis through direct and
indirect action. They are controlled by a series of factors.1
Erosion occurs in different ways. 2
Sedimentation:
beaches, bars,
barrier spits,
pendent terraces,
storm deposits
These make up forms and
deposits which characterize
both high and low coasts.
They are controlled by a
series of factors. 3
1. Geographical features of basin, orientation and contour of coasts, climate, presence of terrestrial
or marine glaciers, anthropic works, river debris, role of organisms, geological features of rock.
2. Abrasion, mechanical erosion, cavitation, leaching, bio-erosion, marine corrosion.
3. Eustatic oscillations, Quaternary tectonics and dynamics, volcanic activity, subaerial exogenous processes
20
Types of erosive sea action
Luigi Carobene
Abrasion. Mechanical erosion
caused by mutual collision or friction
of pieces of rocky debris against
each other or between debris and
substrate rock (rasping effect). This
causes the smoothing of hard rock
surfaces (e.g., limestone). Abrasion
is similar to corrasion caused by
moving water in rivers and winds in
deserts.
Mechanical erosion by waves.
Caused by physical actions in
general, and particularly by the
collisional power of waves against
cliffs and in shallow water. This
causes the rock to break and chip,
followed by excavation and removal
of debris, understood as removal of
rocky fragments produced by the
collision of waves. It is similar to the
quarrying action (block erosion)
caused by tongues of ice.
Cavitation. Phenomenon whereby air
bubbles (water vapour) formed by
wave turbulence (where waves break)
implode (collapse) due to increased
pressure deriving from the collision of
waves against rocky walls.
Water bubbles (cavities) dissolve
rapidly and noisily, producing
mechanical effects.
Leaching. Action of water against soft
rock (e.g., limestone, gypsum),
leading to production of ions.
Bio-erosion. Biochemical or
biomechanical actions directly or
indirectly caused by living organisms.
In the intertidal zone, bivalves,
gastropods, limpets, barnacles, algae,
sponges, worms, sea urchins, etc.
contribute to rock erosion, by means
The sea cliff on the top of which Vieste
(Gargano, Apulia) is built
of boring (e.g., date mussels),
scraping, uprooting and crumbling.
Marine corrosion. Series of mainly
chemical actions which produce
progressive weathering of rock
surfaces and debris (solution,
hydrolysis, hydration, carbonation,
oxidation). Here, rock weathering is
favoured by alternating phases of
wetting and drying associated with
tides or storms (direct action).
Weathering is also caused by
windblown water splashing against
high areas of cliffs. Corrosion
therefore occurs both in intertidal
zones, and in higher areas which are
not splashed by waves directly.
Here, salty spray may cause salt
weathering of the cliff flank,
weathering in general and, in cold
climates, even congelifraction
(mechanical action).
The transformation of waves. When waves reach shallow water, i.e.,
when their half-length exceeds their depth, they become deformed: their
height and steepness increase, and their length and speed decrease, but
they maintain their period. At a certain depth, called breaking depth, they
break, and their crests roll forward. Waves which oscillated in deep water
now become translational, and the water mass “works” both on the sea bed
and against cliff walls.
Only when waves exceed a certain height (critical value) do they have
erosive effects. The figure below shows the important role played by the
depth of seabeds in transforming waves approaching cliffs.
The splashing of waves against the sea bottom produces the important
phenomenon called diffraction. If coastlines are irregular, waves tend to
concentrate their power on protruding sections (promontories) which they
erode, and deposit debris, which supplies beaches in indented areas such
as bays and inlets.
●
r
d
r
d
r
Reflection of waves on flank in deep
seabeds. Flanks undergo hydrostatic
pressure variations, not shock pressure.
Energy is mostly transmitted to reflected
waves. There is little erosion of seabeds and
flanks.
Symbols: d = crest of direct wave;
r = crest of reflected wave; dotted line: shape
of wave when two waves overlap.
Depth is such that it produces intense wave
deformation and breakers roll forwards
against flanks.
Maximum shock pressure.
Energy is expended on weathering of rocks
and turbulence.
Maximum erosion at cliff foot.
Shallow water causes breakers to form
offshore.
Most energy is expended before reaching
cliff foot.
Maximum seabed abrasion.
Different effects of waves against a vertical rock wall, at varying depths
21
■ Cliff dynamics
22
23
The flanks and cliffs of high coasts change over time, sometimes slowly and
continually, at others intermittently or quickly. It is therefore necessary to
speak of the mean speed of these transformations, which is calculated in the
long term (generally more than 50 years).
These mean values, which are now calculated by analysing topographic and
bathymetric maps and by comparing photographs taken over the years, tend
to change with the changing climate, as shown by palaeo-climatological
studies.
In addition, also the breaker zone - the point at which waves strike the shore –
changes over time, due to upward tectonic movements on emerging coasts
and to glacio-eustatic oscillations in sea level, i.e., shoreline changes (see
chart below). These factors determine cliff dynamics.
only subaerial
processes:
weathering,
pedogenesis,
flow, river ravinement,
solifluction, etc.
cliff edge
action of exogenous
agents
supply of debris
RECENT AND PRESENT ANCIENT AND PRESENT
Cliff dynamics
FLANK
CLIFF
recession
indirect marine action
indirect marine
action at cliff foot
TECTONICS
PRESENT
EUSTATISM
debris removal
foot of cliff
SEABED
High coast near San Cesareo (Salento, Apulia)
The present contour of high coasts
is due to the various groups of
processes shown in the figure.
These processes occur over time in
different ways, and with varying
intensity and effects, according to
climatic changes.
-Flank, cliff and seabed are the
three main forms of coastal profiles;
they change continually over time.
-Tectonics and eustatism produce
“changes in shoreline position” (see
chart, page 11).
-Variations in the ratio
supply/removal of debris changes
erosion at cliff foot over time.
Processes affecting cliffs are
shown in the figure “Cliff modelling”
(page 24).
24
CLIFF MODELLING
subaerial processes:
weathering
decalcification
exfoliation
wind abrasion
runoff
ravinement
falls
AGENTS
PROCESSES
RESULTS
Cliff evolution. Analysis of cliffs has led
to the identification of three evolutionary
stages in their development: active,
inactive, and fossil cliffs (see figures on
this page).
Active cliffs are exposed to attack
by subaerial and marine processes,
and therefore they continually recede
over time, supplying the sea with
debris. Their steepness shows the
homogeneity of their rocks and
variations in relations between subaerial
and marine erosion.
1. Active
subaerial and
marine processes
platform formation
●
taphons: alveolar
cavities caused by wind
unstable
zone due
to erosion
at foot
cliff recedes
(due to falls, overturning,
sliding, landslides)
wetting
weathering
salt weathering
WI
ND
waves breaking
towards shore
salty spray
erosion
abrasion
corrosion
leaching
bio-erosion
compression
cavitation
grooves
hollows
grottoes
Inactive cliffs have bases covered
with and therefore protected by flank
debris (scree, alluvial cones, landslides),
and therefore are not subjected to
marine erosion. Their steepness tends
to decrease and their peaks round off.
This is due both to the lowering of sea
level and to the advance of the
shoreline caused by large deposits of
rock and soil.
2. Inactive
stable abandoned
subaerial modelling begins
gradient decreases
●
salty aerosol
receding
debris and
alluvial cones
lowering
of sea level
3. Ancient
fossil, degraded palaeo-cliff
modelling of cliffs
and flanks
alluvial cones
BREAKING WAVE
hydraulic,
mechanical,
chemical
action
water vapor
bubbles
water
bubbles
suspended
debris
debris deposited
at foot of cliff due
to collapse
transport of rocks:
shorewards
offshore
along coast
CURRENTS
weathering of granules
dragged along seabed
abrasion of
rocky seabed
Fossil cliffs are no longer subjected
debris flows
to any form of marine process (e.g.,
due to tectonic rises or eustatic
emersion of area
lowering), and are therefore eroded
and moulded by subaerial processes.
Watercourses flow through them and deposit alluvial cones at their base.
●
The main factors which control these stages are vertical tectonic movements,
eustatism, climatic variations, and, locally, human activities.
Cliff stability. Cliff dynamics often cause instability and hazard. It is therefore
necessary to describe what is involved, the actual possibility of collapses and
rock falls, and what can be done to avoid danger.
25
26
The figure below shows a very simple situation: a cliff of height H between the
surface of a flank and that of the seabed. Taking into account some geometric
parameters (angles, depth, height), the geotechnical parameters of the rocky
mass and wave characteristics, we identify cliff stability by means of two
indexes: stability (s) and breaking (lb).
If ls = about 1, the cliff is unstable; recession is quick and landslides are a
likely hazard.
If ls = about 0, the cliff is stable; recession is very slow, and hazardous
situations are unlikely.
If we consider the breaking index, cases are:
lb = 1, which corresponds to maximum wave pressure on cliffs, implying
erosion, cavitation, absence of beaches, and formation of shore platforms.
lb > 1 corresponds to little or no mechanical erosion. Waves are reflected on
cliffs, which are subjected to hydrostatic pressure only.
If lb = 0, the cliff is protected.
However, in reality situations may be very complex and different, and may
involve not only cliffs, but also flank-cliffs and flanks. These require
specialized geological research on the following:
- Structure of the rock behind the cliff, up to perhaps hundreds of metres or
a few kilometres;
- Quaternary tectonics;
- Detailed stratigraphic analysis, to show stratification and lithological changes,
particularly the overlap of rocks with differing deformability and erodibility;
- The position of the surface separating the two bodies;
- Analysis of rock weathering and permeability;
- Evaluation of the state of vegetation cover and infiltration of water in the
subsoil;
- Morphological study to identify superficial breaks in the soil, which show
rotational movements of the substrate or deep gravitational movements
caused by the cutting of cliffs.
D = depth of cliff foot
Db = breaking depth
H = cliff height
FLANK
β
upper cliff edge
CLIFF
H
features of
rocky mass
features of breaking waves
D
θ
foot of cliff
Db
SEABED
α
Geotechnical and geometrical elements of a cliff: taking into account only the geometrical aspects of a
cliff, the nature of waves and the characteristics of the rocky mass, cliff stability is defined by two
indexes: stability (ls = H/Hc) and breaking (lb = D/Db). The rocky mass is composed of: c’ = cohesion;
ϕ = angle of internal friction; γ = specific weight of rock. Breaking waves are characterized by: direction; offshore height Ho; offshore length Lo. Critical height Hc depends on rock parameters and cliff
gradient.
Present-day notch in Jurassic limestone at Maladroxia (Sardinia)
27
28
Erosion forms of cliffs and platforms
Marine grooves. Horizontal cavities in
cliff flanks at sea level. The shape of the
cavity is generally asymmetrical; the
base is often flat and the vault
hyperbolic (see figure). The shape and
dimensions of grooves depend on the
type of cliff, rock, tide variations, wave
energy, and debris suspended in water.
Generally, grooves form on limestone
cliffs, which sometimes contain “fossil”
grooves, many metres above the present
sea level, formed through leaching, bioerosion and abrasion.
underground karstic cavities. The size
and shape of grottoes depend on these
characteristics, but also on variations in
sea level. In this case, the development
of cavities is heterogeneous and occurs
over hundreds of thousands of years.
Ancient sea levels inside limestone
grottoes produced typical grooves due
to boring action by date mussels.
Grottoes, like grooves, are also
frequently found in compact, resistant
limestone, implying the importance of
chemical processes and bio-erosion.
Grottoes. Cavities sometimes
characterizing cliff flanks, which were
excavated by the sea in areas where the
rock broke, near faults or soft rock
layers. Grottoes may also be found
where there are pre-existing
Ramps. These are often found at the
foot of receding cliffs. They slope
towards the sea (a sort of slide) and link
the cliff flank with the sloping surface of
the platform in front. They are formed by
the abrasive action of waves rich in
debris (abrasion ramps).
Natural arches. Passages formed by
waves near rocky projections (small
promontories) along high coasts. They
form along particular erosion planes,
such as layers or fractures. The erosive
cavity acquires a more stable arched
shape over time. Arches, particularly in
soft rock, are ephemeral in coastal
landscape.
Stacks. Column-shaped rocks, isolated
or in small groups, which are found
along cliffs not far from the shore. They
are relicts of part of the rocky coast
which receded over time due to marine
erosion. The genesis of faraglioni is
favoured by faults and systems of
fractures which, subjected to erosion,
are then separated from the mainland.
Grottoes, developing as a result of fractures in
Mesozoic limestone (Sardinia)
Rocks. Rocky masses which emerge for
a few metres from the sea and are
Luigi Carobene
intensely degraded by waves and
weathering. They may be rocky
emersions, relicts of coastal recession,
or fallen rocks not truly attached to the
seabed.
Bastions. Long, narrow ridges, a few
metres above sea level, formed by the
selective erosion of waves and arranged
at the seaward limit of sea platforms.
Their formation is favoured by resistant,
sloping layers and fractures. As they rise
parallel to the coast, they modify the
action of waves and currents.
Erosion kettles. These generally form
on the surface of platforms and are due
to the action of waves on pebbles
trapped in the uneven seabed. The
pebbles are continually moved and
rounded by the waves and excavate
circular cavities by means of abrasion.
The shapes of kettles vary, and they may
be up to 1-2 metres wide.
Pools. Cavities a few centimetres or
decimetres deep, and several dozens of
centimetres wide, with a flat bottom
which is larger than the opening. They
widen by means of chemical and biochemical processes, favoured by water
stagnation.
Domed forms. Elevated forms with thin
stalks supporting domed shapes. They
may be some decimetres high. Domed
shapes form in the intertidal belt of
platforms.
Pinnacles. These are rocky crests with
irregular, sharp surfaces full of small
cavities. They are formed by corrosion
caused by salt splash and rain in the
area above the high-tide mark.
Limestone bored by date mussels (Sardinia)
Pit (honeycomb). Small, hemispherical
or spherical cavities, usually less than
1 cm across, typical of pinnacle and
pool surfaces.
Trottoirs. Narrow platforms sometimes
found in intertidal zones, between
shoreline and sea. They are divided into:
1) corrosion trottoirs - flat, horizontal
surfaces at high-tide level, cut into the
substrate surface and ending seawards
with an intertidal organogenic shelf;
2) bio-constructed trottoirs - the flat
upper surface of organogenic bodies
(covered with vermetids, serpulids and
calcareous algae), generally at low-tide
level or at mean sea level. Sometimes
centimetres of bioherm cover corrosion
trottoirs. Organogenic frames may
extend seawards for over one metre.
29
30
■ Characteristic aspects of rocky coasts
Rocky shores sometimes have peculiar eroded forms or deposits which are
due to many coastal processes, the sea level and its variations, type of rock,
the activity of certain organisms, cliff recession and climatic conditions.
Major forms. The transition from platform to cliff is often marked (especially in
carbonatic rock) by grooves, indicating a period of steady sea level; certain
structural conditions give rise to gullies sometimes several metres deep,
called sea grottoes. Relative variations in sea level may widen these grottoes,
making them dozens of metres deep. Ramps, with slightly concave surfaces,
may form between platforms and cliffs.
In other cases, and in particular climatic conditions, the transition between cliff
Natural arch at Capo Palinuro (Campania)
and sea is marked by narrow subhorizontal surfaces (platforms, banks,
ledges) of mainly organogenic origin.
The area in front of cliffs may contain
monolithic rocks (faraglioni), emerging
rocks and arches, which highlight the
dynamics of the coastal environment
and particularly cliff recession. Shore
platforms sometimes have rocky
bastions on their seaward side.
Minor forms due to karstic erosion.
These are found along certain high
coasts on carbonatic rocks (limestone,
calcarenite, or cemented carbonatic
sand). They are produced by the
mechanical action of waves, but
particularly by marine corrosion
enhanced by alternating periods of
emersion and submersion, besides
stagnation of plant matter inside
hollows in the rock.
Maceration of organic matter acidifies
water, favouring the solubility of
calcium carbonate. Living organisms
also contribute to erosion, as they
burrow small hollows in the rocky
walls.
An important factor controlling and
further developing these forms is
climate. Research shows zoning of
forms from the coast seawards with
small pools, pinnacles with holes on
cliff surfaces (a few metres high);
hollows, niches dug out by organisms
and small pools on cliffs; kettles and
grooves at the cliff base, and domed
surfaces and asymmetrically shaped
pools on abrasion platforms.
a
b
c
d
Some of the erosive forms found along
coasts between high and low tide, or in the
upper area which is affected by storms and
salt spray.
These forms may change according to
position, tides, and type of rock.
a. Corrosion pools (biochemical processes,
with dissolved calcium carbonate due to
stagnating water inside);
b. Kettles (abrasion carried out by pebbles);
c. Domed surfaces (abrasion by waves);
d. Pinnacles (corrosion, bio-erosion, leaching)
31
Terrestrial flora and vegetation
SIMONETTA PECCENINI
■ Living conditions
The main limitation to the life of plants
on cliffs and detrital coastal slopes,
subjected as they are to the direct
effects of the sea, is the high
concentration of salt in the soil. Plants
which can withstand or even prefer
high salt concentrations are called
halophilous. Their tissues often have
cells rich in mucilage, which retains
water. Other species, non-exclusive to
Tyrrhenian cornflower (Centaurea aplolepa
this environment, develop these
ligustica)
characteristics when they grow here.
When Tyrrhenian knapweed (Centaurea aplolepa ligustica) colonizes rocks
covered with salt, it turns into a kind of succulent plant: its leaves become thick
and fleshy, its parenchyma swells with water, and the outer surface of its
epidermis thickens. If there were no transition between these halophilous forms
and those with normal structures, one might even think they were different
species.
Another factor which hinders life on rocks is the lack of substrate, which
accumulates only in a few cracks. Here we find only chasmophytes, i.e., plants
adapted to life in cliff cracks.
Protracted exposure to sun and salt often determine arid conditions, and living
species therefore feature xerophilous adaptations (from the Greek xeròs = dry,
arid), such as small leaves covered with hairs or wax to limit transpiration.
Substrates on detrital slopes are incoherent, and landslides often hinder
vegetation. In these conditions, only species with robust root systems can
survive.
The distribution of vegetation also depends on weather phenomena, among
which wind is one of the most important. The resulting vegetation is composed
mainly of chamaephytes, i.e., small, woody, prostrate or pulvinate (cushion-
Rocky coastline near Santa Cesarea (Salento, Apulia)
33
34
Sea fennel (Crithmum maritimum)
shaped) plants which grow flat on rocks to maximize their resistance to the
strong sea winds. The plant cover near the sea is therefore usually composed
of species belonging to all these categories at the same time: halophilous
chasmophytes, and xerophilous and pulvinate or prostrate chamaephytes.
The species most resistant to saltiness, those which colonize areas nearest to
the sea, creeping into cracks or consolidating landslide debris, are sea fennel
(Crithmum maritimum), sea lavender (Limonium spp.) and a few other species;
however, the greater the distance from the sea, the larger the number of
species.
■ Flora
Let us now list the most interesting or most frequent species found on Italian
rocky shores.
Among conifers are Aleppo pine (Pinus halepensis), with its light foliage and
pale bark, cluster pine (Pinus pinaster), with hard needles, sharp cedar
(Juniperus oxycedrus), with sharp needles and red berries, and Phoenician
juniper (Juniperus phoenicea), its branches covered with small, imbricate,
squamiform leaves.
Camphor tree (Camphorosma monspeliaca), a small chamaephyte with a
woody base, prostrate-ascending stalks bearing thin, linear leaves, and spikes
with clusters of tiny flowers, may be
also found inland, in sub-salty, silty
areas.
Caryophyllaceae are common on rocky
coasts, e.g., Paronychia capitata,
found in western Liguria and Sicily, and
strong-rooted spurrey (Spergularia
macrorhiza), endemic to cliffs in
Sardinia and Corsica. Then there is
campion with gaudy flowers: nodular
campion (Silene nodulosa), with
pinkish-white petals, is endemic to
cliffs in Sardinia and Corsica; fruticose
campion (Silene fruticosa), with pink
flowers, lives on limestone cliffs in
Sicily; hairless catchfly (Silene vulgaris
ssp. angustifolia), a subspecies
associated with cliffs and arid areas by
the sea along all Italian coasts, has
white flowers with a typical swollen
calyx and fleshy, blue-green, opposite
leaves; and sedum-leafed campion
(Silene sedoides), an annual with tiny
rosy-white flowers borne on reddened
undeveloped stalks, lives in Tuscany,
Apulia, Sicily and Sardinia.
Cracks in coastal cliffs host the
beautiful flowers of various species of
wild pinks, e.g., Balbis pink (Dianthus
balbisii) in Liguria and cliff pink
(Dianthus rupicola) in southern Italy and
Sicily. The latter species is a perennial
with blue-green, sharp, coriaceous,
fleshy leaves attached at the base and
clusters of rosy flowers.
This is a suffruticous chamaephyte
which blossoms in summer and is
found in Cilento, southern Calabria and
Sicily; it is also a mesophilous and
35
Paronychia (Paronychia capitata)
Sedum-leafed campion (Silene sedoides)
Balbis pink (Dianthus balbisii)
36
Common caper (Capparis spinosa)
thermophilous chasmophyte and lives, as its name suggests, on limestone
cliffs and sometimes on old walls, such as those of the castle at Milazzo, on the
northern Sicilian coast. The pinks commonly grown in the nursery hot-houses
along the Ligurian Riviera seem to derive from cliff pink.
Cliffs in Sardinia and on the tiny island of Lampedusa are the only places where
Egyptian St. John’s wort (Hypericum aegypticum) grows - a small, woody,
steno-Mediterranean shrub.
Capers are very often found on old walls and limestone cliffs. Common caper
(Capparis spinosa) lives throughout Italy, and hairy caper (Capparis ovata) is
found in southern Italy, from Calabria to Gargano, and in Sicily. It is used as a
savoury seasoning obtained from the buds or early fruit of these climbing
shrubs. Caper flowers are white, very large and showy with many long stamens,
blossoming in spring-summer. Its deciduous leaves are round with long stalks.
There are also many crucifers. Hoary stock (Matthiola incana), a stenoMediterranean crucifer, with reddish-purple or white flowers, is found on all
rocky cliffs throughout Italy, from Liguria to the Conero promontory. Malcolmia
(Malcolmia flexuosa) lives only on the Tremiti islands. Lesser vesicaria
(Alyssoides sinuata) and white alyssum (Alyssum leucadeum) which are grey,
downy chamaephytes with large yellow
flowers, are amphi-Adriatic species,
i.e., they live on both shores of the
Adriatic. They may also be found in
Dalmatia, but in Italy the former
colonizes only the limestone cliffs of
Gargano and Murge, and the latter the
areas around Otranto, Gallipoli, Castro,
and the Tremiti islands (Apulia).
Common alyssum (Lobularia maritima),
with honey-scented white or sometimes
purplish-red flowers, is found all over
Italy, not only near the sea but also in
dry areas and on walls.
Candytuft (Iberis semperflorens) forms
hemispheric, evergreen shrubs, with
strong, woody twigs covered with the
scars of its fallen leaves. The cuneatespatulate leaves are smooth, fleshy,
with short stalks, completely covered
with clusters of flowers which form a
thick umbrella-shaped corymb. Its
scented flowers have an irregular
corolla, as the two external petals are
three times as large as the others,
which are white, sometimes rosy,
spatulate, and contracted at their base.
This is a suffruticous chamaephyte
which blossoms in mid-winter, forming
beautiful white cushions on rocky
flanks. It is an endemic species and its
distribution is similar to that of cliff pink
(at Capo Palinuro in Campania, in Sicily,
and on the island of Zembra in the Gulf
of Tunis). It is a meso-xerophilous
chasmophyte living on limestone cliffs
up to 1400 m.
Sea kale (Brassica oleracea ssp.
robertiana), the spontaneous ancestor
37
Hoary stock (Matthiola incana)
Common alyssum (Lobularia maritima)
Sea kale (Brassica oleracea ssp. robertiana)
38
“Carrubazzo” (Anagyris foetida)
Bird’s-foot trefoil (Lotus cytisoides)
Jupiter’s beard (Anthyllis barba-jovis)
of cabbage grown as a vegetable,
is endemic to the north-western
Mediterranean, from Catalonia in Spain
to the Conero promontory near Ancona
on the eastern Adriatic. There are also
other coastal kale species - big-fruit
kale (Brassica macrocarpa), Trapani
kale (Brassica drepanensis), white kale
(Brassica incana), Sardinian kale
(Brassica insularis) - which are less
widely distributed. Kale is a perennial
plant the stalks and twigs of which are
woody at the base and herbaceous at
the top. Its bottom leaves are large,
lyrate, with slightly amplexicaul base
earlets and irregularly crenate edges.
Its blossoms form thick clusters of
yellow flowers. Kale is a suffruticous
chamaephyte with robust foliage and
large flowers which bloom between
February and April. It is also a
mesophilous and thermophilous
chasmophyte, typically found along
both limestone shores and inland.
A new species of kale, the scientific
name of which is Brassica tyrrhena, has
recently been found on limestone
shores in central-western Sardinia,
between Baunei and Dorgali. It grows
in calcareous cracks exposed to the
sun, from sea level up to 500 m, and its
large cobs of yellow, scented flowers
bloom in February-March.
Tyrrhenian and southern Italian regions,
particularly thermophilous maquis,
host carob (Ceratonia siliqua), which
may also be shrub-like, with its shiny,
coriaceous, paripinnate leaves. Its
long, leathery pods contain a sweet,
edible pulp and very hard seeds, which
were used in the past as units of
measure for gold: the term “carat”
derives from the Arabic for carob.
In winter and spring, “carrubazzo”
(Anagyris foetida) blooms and sets
fruit. This is a heliophilous and
thermophilous shrub with deciduous,
trifoliate leaves and yellow flowers. It
occasionally grows along Italian
coasts from Liguria to the Marches
and the islands.
Among the most localized species is
Aeolian cytisus (Cytisus aeolicus),
endemic to the Aeolian islands north
of Sicily, Nurra broom (Genista
acanthoclada ssp. sardoa), typically
found in northern Sardinia, Corsica
broom (Genista corsica), in Corsica
and Sardinia, Moris broom (Genista
morisii), typical of southern Sardinia,
and Cilento broom (Genista cilentina),
on Tyrrhenian shores in Campania and
Sicily. Bird’s-foot trefoil (Lotus
cytisoides), with a woody base, hairy,
silvery trifoliate leaves and golden
yellow flowers, covers cliffs or appears
from cracks in cliffs along Tyrrhenian
and Apulian coasts. Cracks in higher
coastal cliffs, which are not splashed
by the sea, contain Jupiter’s beard
(Anthyllis barba-jovis), a slender shrub
with ash-grey leaves and white
flowers, shrubby scorpion vetch
(Coronilla valentina) and rush-like
scorpion vetch (Coronilla juncea).
Cliffs also host tree spurge (Euphorbia
dendroides), a shrub or small tree with
blue-green leaves which turn red
39
Shrubby scorpion vetch (Coronilla valentina)
Tree spurge (Euphorbia dendroides)
Large Mediterranean spurge (Euphorbia characias)
40
Aleppo rue (Ruta chalepensis)
Tree-mallow (Lavatera arborea)
Cliff tree-mallow (Lavatera maritima)
before falling in early summer. Large
Mediterranean spurge (Euphorbia
characias) is also a large shrub, which
is found in maquis and coastal garrigue
along the Italian peninsula and its
islands. Wulfen’s spurge (Euphorbia
wulfenii), with its funnel-shaped flower
bracts, grows near Trieste, Conero and
Ventimiglia.
Then there are the dense cushions of
strawberry spurge (Euphorbia fragifera)
on limestone screes in Istria, Bivona’s
spurge (Euphorbia bivonae) on Sicilian
coastal cliffs, sea cliff spurge
(Euphorbia pinea) with herbaceous
branches, spiny spurge (Euphorbia
spinosa), the thorny cushions of which
colonize coastal screes and cliffs
throughout Italy and Sardinia, and
Balearic spurge (Euphorbia pithyusa), a
small shrub with a woody base and
dense oval leaves, which, like all
spurge leaves, contain a poisonous
milky latex.
Coastal garrigue contain the aromatic
Aleppo rue (Ruta chalepensis), and
Sardinian granite cliffs host the
endemic Corsican rue (Ruta corsica).
Spurge olive (Cneorum tricoccon), a
shrub the flowers of which have three
petals, is only found in a few locations
along northern Tyrrhenian and
Sardinian shores.
In spring and summer, mallow
blossoms lushly. Species include: treemallow (Lavatera arborea), with purple
flowers, which is spontaneous on
coastal cliffs in southern Italy and its
islands, and runs wild in vegetable
gardens; cliff tree-mallow (Lavatera
maritima), found on cliffs in western
Liguria, Sardinia and on the island of
Gorgona, with downy-grey leaves and
large pink flowers; and Hyères treemallow (Lavatera olbia) found along
western coasts in Apulia and on Italian
islands.
Sericeous daphne (Daphne sericea),
with its twisted twigs and tiny white
flowers, grows on limestone cliffs from
Piombino on Elba to the Tremiti
“Spazzaforno” (Thymelaea hirsuta)
islands; “spazzaforno” (Thymelaea
hirsuta), with yellow flowers and
branches completely enveloped by
small, imbricate leaves, lives in cliff
garrigue along western Italian coasts
and islands; thymelaea (Thymelaea
tartonraira) is only found in Campania,
Sicily and Sardinia.
The cliffs at Capo Mannu (Sardinia)
host the rare bushy violet (Viola
arborescens), a steno-Mediterranean
species with woody stalks and white,
pale blue or violet flowers.
Woody frankenia (Frankenia laevis)
The colourful, yellow flowers of
rockroses bloom for a short period on
cliffs and garrigue: yellow rockrose (Halimium halimifolium) from Tuscany to
Molise and Sardinia; cat’s head rockrose (Helianthemum caput-felis) at Capo
Mannu in Sardinia; Ionian rockrose (Helianthemum jonium), which is endemic
to coasts from Romagna to Basilicata; Mediterranean rockrose (Fumana
arabica), from Tuscany to Apulia and Sicily and Sardinia; thyme-leaved
rockrose (Fumana thymifolia) and Fumana laevipes, which are also found in
Liguria.
Cliffs with salty pools are colonized by small sprawling shrubs of sea heath
(Frankenia laevis) and hairy frankenia (Frankenia hirsuta).
Sea fennel is a densely branched, glabrous, blue-green, perennial umbellifer
with a woody base, and fleshy stalks and leaves. In late summer, it is covered
by large yellow umbels composed of tiny flowers; it bears fruit in September.
41
42
The umbellifer family is characterized by
the presence of aromatic substances
often used in cooking; the fleshy
leaves of sea fennel are also pickled
and used in salads. This coastal, cliffloving species grows along rocky
shores and on cliffs, but may also
adapt to life in debris, pebbles,
consolidated sand, and even in ballast.
It typically associates with other
halophilous plants along the seasplashed coasts of the Mediterranean,
Atlantic, Canary Islands, and as far as
the Black Sea.
In June, the large white umbrellashaped clusters of sea cliff carrot
(Daucus gingidium) dangle from long
Palinuro primrose (Primula palinuri)
scapes surrounded by light, lace-like
segmented leaves. The white umbels of Boccone’s moon carrot (Seseli
bocconi), a perennial, branched plant with a woody base and blue-green
lanceolate or linear lacinia, blossom on limestone cliffs in Sicily and Sardinia.
Mediterranean moon carrot (Seseli tortuosum) is also found along Italian
coastal cliffs and on garrigue.
The rare Lucania moon carrot (Portenschlagiella ramosissima), with linear,
segmented leaves and yellow flowers forming elegant umbels, lives only on
the cliffs of Mt. Bulgheria near Sapri. Among umbellifers is Macedonian
atamantha (Athamanta macedonica), Sicilian atamantha (Athamanta sicula), a
few hare’s ears (Bupleurum elatum, B. dianthifolium, B. fruticosum), honewort
(Trinia glauca), etc..
The most thermophilous heather species (Erica sicula, E. terminalis) colonize
very dry, limestone cliffs in Sicily and shady, humid ones in Campania and
Sardinia, respectively.
Palinuro primrose (Primula palinuri) blooms lushly on Capo Palinuro between
February and March. It is a very rare species, found only on a few north-facing
limestone cliffs between Capo Palinuro and Scalea. It is a suffriticous plant,
with woody stalks and viscous, fleshy, dentate leaves; its yellow flowers form
umbels and have white, floury, bell-shaped calyxes.
The most interesting of the madder family are stinking madder (Putoria
calabrica), rock crosswort (Crucianella rupestris), a few woodruff (Asperula
Ferns
Although the ideal environment for
most types of fern is damp, shady
undergrowth, a few species do live on
coastal cliffs, in particular habitats.
Woodwardia (Woodwardia radicans)
lives in damp ravines and caves in the
Mediterranean area. It has a northernsubtropical distribution, but in Italy it
is only found on the island of Ischia,
Sorrento peninsula, Calabria and
Sicily. Its name derives from the fact
that the axis of its long leaves may
bear new plants as soon as they find
soil. This phenomenon occurs in
deeply shaded areas where this fern
grows lushly together with other, more
frequent varieties, as occurred in the
Tertiary epoch, of which woodwardia
is a relict.
Tyrrhenian shield fern (Dryopteris
tyrrhena) is less frequent. It is found
only in the western Mediterranean, in
a few areas in southern Spain and
France, Liguria, Sardinia, Corsica and
the Tuscan Archipelago. It lives in cliff
cracks, rocky inlets, at the foot of
cliffs, and also on dry walls, but only
on silicic substrates. It is very similar
to the common male fern but its
leaves are more triangular, with
smaller sori (spore clusters).
Madeira lady fern (Cheilanthes
maderensis) also prefers silicic
substrates. It is found in cliff cracks,
on minute debris and dry walls
everywhere in Liguria, on Capraia in
the Tuscan Archipelago, on Vesuvius,
in Sicily, on the small Aeolian island of
Alicudi, on Pantelleria, and in Sardinia.
It has small, horny leaves, the margins
of which curl over their undersides,
protecting the spore-bearing
structures.
Sunny limestone or volcanic cliffs in
Simonetta Peccenini
Acquafredda between Sapri and
Maratea, near Gallipoli, in Sicily, on
the islands of Linosa and Pantelleria,
and southern Sardinia host Catania
lady fern (Cheilanthes vellea). It has
fronds of segmented leaves, with
linear-lanceolate margins and short
petioles. The undersides of its leaves
are covered with scales which form a
rusty felt extending to the sori.
Glandulose spleenwort (Asplenium
petrarchae), a small fern with delicate
pinnate fronds with lanceolate
margins, is completely covered by
gland hairs. It lives in cliff cracks,
coarse debris and limestone. It is a
Mediterranean species and, in Italy, is
found in Liguria, between Sapri and
Maratea in southern Campania, in
Sicily and eastern Sardinia. The Latin
name of the species recalls the wellknown poet and humanist Francesco
Petrarca (Petrarch), because it was
picked and described for the first time
in France, near the “clear, fresh
waters” in Vaucluse which he
celebrated.
Madeira lady fern (Cheilanthes maderensis)
43
44
crassifolia, A. garganica, A. rupestris),
tiny bedstraw (Galium minutulum) and
hairy crosswort (Valantia hispida).
Turkish convolvulus (Convolvulus
cneorum) is a shrub up to 30 cm high,
the stalks of which are silvery,
enveloped in silky hairs, and leafy,
particularly on sterile twigs. Its acute,
lanceolate-spatulate leaves with entire
margin and short leafstalks are white,
downy, and covered in thick hairs. The
many flowers at the tips of its stalks
Savona convolvulus (Convolvulus sabatius)
have hairy calyxes with sharp, rigid
teeth and white, lilac-streaked corollas
which, initially twisted, become conical
and bell-shaped in full bloom.
It is a fruticose chamaephyte which
blossoms in spring (April-May). Its
fragmented, relict distribution includes
Dalmatia, Albania, central-southern
Italy and Sicily. In Italy, it lives on
Tyrrhenian shores (Massa Marittima,
M. Argentario, Gaeta, Sorrento
Peninsula, Capri, near Palermo at
Monte Catalfano, Monte Pellegrino
Tree germander (Teucrium fruticans)
and Monte Gallo, and near Trapani at
Monte Cofano and Capo San Vito). It
is a thermo-xerophilous and heliophilous chasmophyte found on limestone
cliffs up to 700 m.
Endemic to Liguria, Savona convolvulus (Convolvulus sabatius) is even rarer,
and has pale blue-violet flowers, yellow inside. Its scientific name derives from
the old name of Savona: Vada Sabatia. It is spontaneous only at Capo di Noli,
near Savona, on inaccessible dolomitic cliffs plunging into the sea. As it has
beautiful flowers, it is often grown in gardens, and also tends to run wild in
Apulia and Sicily.
Among plants of the mint family are tree germander (Teucrium fruticans), yellow
germander (Teucrium flavum), cat-thyme (Teucrium marum), Mediterranean
prasium (Prasium majus), sticky hedge nettle (Stachys glutinosa), Sardinian
savory (Satureja thymbra), micromerias (Micromeria filiformis, M. microphylla,
M. nervosa, M. graeca, M. canescens,
M. cosentina, M. fruticosa) and
streaked thyme (Thymus striatus).
White henbane (Hyosciamus albus), a
poisonous member of the potato
family, with pale yellow, bell-shaped
flowers in spikes, is slightly nitrophilous
and is therefore found on cliffs and
walls, especially where seagulls nest
and tourists sunbathe.
Among the figworts are fruticose
figwort (Scrophularia frutescens) and
snapdragon, which are usually grown
in gardens for their colourful flowers.
Yellow
snapdragon
(Antirrhinum
latifolium) lives on shores in Liguria,
Tuscany,
and
Latium;
bushy
snapdragon (Antirrhinum tortuosum)
and Sicilian snapdragon (Antirrhinum
siculum) live on the Tyrrhenian shores
of Latium, Calabria and Sicily; common
snapdragon
(Antirrhinum
majus)
everywhere, usually escaping from
gardens. Snapdragon is a perennial
herbaceous plant, shrubby and woody
at its base, with straight stalks, linear or
elliptical leaves, opposite at the bottom
and alternating in the upper part.
According to species, their pale yellow,
pink or purple-red corollas have that
typical shape which gives the common
name to the plant. Their fruit is a
capsule, and they bloom and fructify
almost all year round.
The cliffs and walls of the Italian
peninsula and Sicily host purple
toadflax (Linaria purpurea); Capraia
toadflax (Linaria capraria) is endemic
to the Tuscan Archipelago. Sicilian
45
Mediterranean prasium (Prasium majus)
White henbane (Hyosciamus albus)
Yellow snapdragon (Antirrhinum latifolium)
46
Savona bellflower (Campanula sabatia)
toadflax (Cymbalaria pubescens) is
endemic to Sicily, and Tyrrhenian
toadflax (Cymbalaria pilosa) lives on
cliffs from the Circeo promontory near
Rome to Calabria. Salty cliffs host
plantain (Plantago coronopus), with
rosettes of fleshy, laciniate leaves.
Red valerian (Centranthus ruber) is
found everywhere, whereas cliff
scabious (Scabiosa cretica) of Calabria
and Sicily and Trapani scabious
(Scabiosa limonifolia), endemic to
Sicily, are rare.
Sicilian
bellflower
(Trachelium
lanceolatum) with beautiful corymbs of
violet flowers, is endemic to shady
Sicilian cliffs. Savona bellflower
(Campanula sabatia), endemic to
calcareous rocks in western Liguria,
lives in coastal garrigue. Limestone
cliffs host endemic bellflowers with
small, cordate or reniform leaves and
cascades of pale blue, star-shaped
flowers: Bethlehem stars (Campanula
isophylla), endemic to limestone rocks
in western Liguria; Adria bellflower
(Campanula garganica), endemic to the
Gargano (the “spur” of the Italian boot);
Neapolitan bellflower (Campanula
fragilis) endemic to southern Italy;
and Apulian bellflower (Campanula
versicolor), which belongs to the same
group and lives in Apulia and Greece.
On cliffs of the Italian islands are
delicate daisies, the heads of which
are yellow, surrounded by white or pink
ligular petals: tiny daisy (Bellium
minutum) on Pantelleria, Linosa and
Lampedusa, is annual. False daisy
47
Bethlehem stars (Campanula isophylla)
Neapolitan bellflower (Campanula fragilis)
Phagnalon (Phagnalon graecum illyricum)
48
Strawflower (Helichrysum stoechas)
Porto Venere knapweed (Centaurea veneris)
Maritime aster (Asteriscus maritimus)
Gargano knapweed (Centaurea subtilis)
Dusty miller (Senecio cineraria)
Tremiti knapweed (Centaurea diomedea)
(Bellium bellidioides) and thick-leaved
daisy (Bellium crassifolium) are
perennial and live in Sardinia.
Cliffs, walls and garrigue host the
greyish cushions of phagnalon
(Phagnalon sordidum, P. rupestre, P.
saxatile) and the large, yellow flowers of
strawflower (Helichrysum stoechas, H.
saxatile, H. rupestre, H. siculum).
Maritime aster (Asteriscus maritimus)
grows in dense shrubs with hairy stalks
and spatulate leaves. In spring, it is
covered with large yellow flowers.
The large shrubs of groundsel
(Senecio cineraria, S. bicolor) are
often to be found. White, woolly hairs
cover their twigs and leaves, which
Common reichardia (Reichardia picroides)
are indented to the central nervation,
and corymbs have yellow heads with white, woolly bracts.
Coastal groundsel (Senecio leucanthemifolius) is a small, annual plant, the
yellow flowers of which blossom in winter. Dusty miller (Centaurea cineraria)
and the similar Centaurea gymnocarpa, Porto Venere knapweed (Centaurea
veneris), Aeolian knapweed (Centaurea aeolica), Leuca knapweed (Centaurea
leucadea) and Ucria knapweed (Centaurea ucriae) of western Sicily, are a group
of meso-xerophilous and heliophilous chasmophytes endemic to coastal and
subcoastal cliffs. They are ash-grey, downy perennial plants with straight stalks,
woody at the base, laciniate leaves, and rosy or purple flowers in small heads.
They are suffruticous chamaephytes which blossom in summer.
Limestone cliffs also host other species of knapweed, such as Taormina
knapweed (Centaurea tauromenitana), endemic to eastern Sicily, spiny
knapweed (Centaurea horrida), of northern Sardinia, Oliena knapweed
(Centaurea filiformis), endemic to eastern Sardinia, Tyrrhenian knapweed,
which lives along the Ligurian and Tuscan shores, Karst knapweed (Centaurea
kartschiana), endemic to the karst, Gargano knapweed (Centaurea subtilis),
typical of Apulia and Basilicata, Parlatore’s knapweed (Centaurea parlatoris), in
Sicily, Tenore’s knapweed (Centaurea tenorei), on the Sorrento peninsula, and
Tremiti knapweed (Centaurea diomedea) on the Tremiti islands.
There are also members of the chicory family, such as smooth cat’s ear
(Hypochoeris laevigata), marine sow thistle (Sonchus asper ssp. nymani), a
49
51
50
Tyrrhenian iris (Iris chamaeiris)
Dwarf palm (Chamaerops humilis)
biennial or perennial plant with thorny, blue-green leaves and large, yellow
heads; common reichardia (Reichardia picroides), with yellow flowers and
green leaves with red and pale blue shades; spiny chicory (Cichorium
spinosum), a hemi-spherical shrub with pale blue flowers; sea cliff chicory
(Hyoseris taurina); wild chicory (Hyoseris radiata) and Spanish chicory
(Hyoseris baetica).
In the iris family are several endemic and steno-Mediterranean irises of
heliophilous, thermo-xerophilous habit. They colonize rocky limestone
substrates and garrigue: Tyrrhenian iris (Iris chamaeiris), on the western coast;
Salentine iris (Iris revoluta) in Apulia; Todaro’s iris (Iris todaroana) in Sicily and on
the island of San Pietro, off Sardinia; and Sicilian iris (Iris pseudopumila) in
Apulia and Sicily. The last is a perennial plant with short, horizontal rhizomes,
and cylindrical stalks enveloped by the sheathing base of the leaves. Its single,
scented flowers are yellow with violet edges or vice versa, and are enveloped by
membranous spathes. Its spatulate laciniae have a central line of dense hairs:
the three external laciniae are turned out- and downwards, the three internal
ones converge, hoodlike. Its leaves are blue-green, sharp and lanceolate. It is a
rhizomatous geophyte with persistent leaves, which blossoms in spring.
Shore cliffs often host gramineae such as curved ryegrass (Parapholis incurva),
slender barb grass (Lepturus incurvatus), orchard grass (Dactylis glomerata
ssp. hispanica), lamarckia (Lamarckia aurea), ryegrass (Catapodium marinum),
and Oryzopsis coerulescens. Dwarf palm (Chamaerops humilis), small, with
fanned leaves, is the only species of the palm family to grow spontaneously in
Italy. It may be found on limestone shore cliffs and in thermophilous maquis.
This short list shows how rich, especially in endemic plants, is flora living on
coastal cliffs, and one may wonder why, in view of the apparent harshness of the
habitat. The answer, as often happens when discussing biological phenomena,
is complex, because it implies the interaction of many factors. One of the most
important ones is the history of vegetation in Italy. In the early Tertiary, the
vegetation was probably tropical, with large, tree-like ferns and lush palms,
which were then replaced by laurels and magnolias when changed climatic
conditions made tropical vegetation migrate south. In the Pliocene, therefore,
vegetation became xerophilous and evergreen, similar to the present one. The
variety of border environments along rocky shores may be a refuge for many
plant species which have alternated over time. A classic example is dwarf palm.
Links between emerging lands were different from today’s in both the Tertiary
and Quaternary, perhaps explaining now disjunct distributions such as the
amphi-Adriatic one of white alyssum, or the western Mediterranean of bushy
violet, found in France, Spain, the Balearic Islands and Sardinia.
The subdivision of widely distributed species caused the birth of new species
confined to restricted areas, starting from populations which were isolated
from the mother species. For example, Bethlehem stars, Adria, Neapolitan and
Apulian bellflowers all belong to the same group of species, originating from a
common ancestor.
52
Exotic plants
The ecological conditions of rocky shore
habitats enable the development of
plants native to foreign countries with a
similar climate. These exotic plants were
intentionally or unintentionally brought to
these areas by man. They are obviously
adapted to Mediterranean or tropical
climates and come from various
countries: South Africa, Central and
South America, Asia Minor, etc.. Many of
them are succulents, i.e., they contain
water-retaining mucilage, as water is
always insufficient in their native
environment.
One of the most well-known is agave, or
century plant (Agave americana) which,
as its scientific name suggests, comes
from Central America. It was introduced
into Italy (Tuscany) in the 16th century
and from there spread throughout the
Mediterranean - to such an extent that it
is now a typical feature of the landscape.
It spreads mostly through vegetative
reproduction, but it also produces many
seeds before dying. Century plants are
monocarpic, i.e., they flower only once
in their lives, bear fruit, and then die.
Their long, rigid, thorny leaves envelop a
single scape - a leafless stalk - which
may be several metres long, bearing a
greenish-yellow flower spike.
Aloe (Aloe barbadensis) is similar to
century plant, although smaller and less
widespread. It is a woody plant with
fleshy, toothed, spiked leaves, in the
middle of which grows a scape bearing
yellow bell-shaped flowers. The
introduction of aloe into Europe was very
complicated: native to eastern Africa,
Saudi Arabia and India, it was later
grown in the Caribbean, where it ran
wild, and from there it was introduced
into Europe with the name
“barbadensis”, suggesting that it
Simonetta Peccenini
Agave (Agave americana)
Hottentot fig (Carpobrotus edulis)
originated in Barbados. Gardens near
cliffs in Liguria, Campania, Calabria and
Sicily also host other aloe species, some
of which have interesting medical
proprieties and are used for their antitumoral effects.
Another exotic species, now a common
sight in the Mediterranean, is prickly
pear (Opuntia ficus-indica). It belongs to
the cactus family and is native to Central
America. It was introduced into Europe
by Christopher Columbus, and since
then has been grown for its edible fruit
and also to create impenetrable hedges.
Its fleshy, flat, segmented joints, called
cladodes, are covered with thorns.
Hottentot figs (Carpobrotus acinaciformis,
C. edulis) are native to South Africa, but
find Italian climatic conditions along the
coasts so favourable that they have
become invasive. They have long,
creeping stalks with opposite, triangular,
fleshy leaves, with large purple flowers in
the former species and yellow or red in
the latter.
Yellow sorrel (Oxalis pescaprae) is also
native to South Africa, but has spread in
the Mediterranean over the last two
centuries and is now found in olive groves
and orange orchards, on uncultivated
land and along roads. In Italy, it spreads
by means of bulbils, whereas in its native
country it reproduces sexually. It blooms
with spectacular yellow flowers in winter
and spring. In summer, both its trifoliate
leaves, rich in oxalic acid, and its stalks,
dry up completely.
Heart-leaf ice plant (Aptenia cordifolia) is
native to South Africa and is grown in
gardens along the coast. It often escapes
from them and covers shores, rocks and
old walls with its small, heart-shaped
fleshy leaves and tiny purple flowers
which bloom throughout the year.
A few groundsels (Senecio angulatus, S.
mikanioides) also come from South
Africa, and are called ornamentals
because they flower in November and
December. S. angulatus, more common
than S. mikanioides, grows
spontaneously on cliffs, walls and sunny
slopes along Tyrrhenian, Ionian and
southern Adriatic shores. They both
have lianoid habitus, with yellow flower
heads arranged in corymbs, and small
fleshy leaves which resemble ivy.
Castor-oil plant (Ricinus communis) has
been cultivated since ancient times to
extract oil from its seeds, and it soon
escaped from gardens. It is a member of
the spurge family, native to the tropical
European belt. It has large shield-shaped
leaves, i.e., round, with petioles inserted
in laminas, and many toothed lobes. In
favourable climatic conditions, as in
Sicily, its herbaceous or trunk-like stalk
may be several metres tall.
Garden waste is sometimes completely
covered by the yellow and reddishorange flowers of nasturtium
(Tropaeolum majus). This is an annual,
with creeping stalks and almost round,
shield-like leaves, native to South
America. It is commonly grown in pots
on balconies and in gardens, and its
greyish, wrinkly seeds germinate very
easily, colonizing the environment.
Tree tobacco (Nicotiana glauca) is a
small tree with bluish leaves and yellow
trumpet-shaped flowers which bloom
throughout the year. Native to South
America, it is pot-grown or runs wild on
cliffs, old walls or debris near gardens,
and all along the Italian coastline.
Much rarer is the shrub Wigandia
caracasana of the waterleaf family, which
grows only in gorges and uncultivated
land in Sicily and the western Ligurian
coast. Native to Central-South America
(from Mexico to Venezuela and
Colombia), it is grown as an ornamental
for its dichotomous tips, pretty lilacwhite flowers, and large leaves with
yellowish, hairy undersides.
Tree alfalfa (Medicago arborea) has
become spontaneous in Italy, but is
certainly native to Greece and Asia
Minor. Study of its distribution reveals
that it is found where ancient Greek
colonies arose, and therefore, although
we may call it an exotic plant, it was
introduced in ancient times. It is a shrub
up to 4 m high, with silvery, hairy
trifoliate leaves and yellow flowers.
53
■ Vegetation
54
Golden samphire (Inula crithmoides) on the carbonatic rocks of Cilento (Campania)
Bare soil is colonized by pioneering plant
species which have few requirements, are
only slightly competitive with others, and
are replaced by more demanding species
as soon as a sufficient amount of substrate
forms.
As regards cliffs - of any sort - this does
not occur: pioneering vegetation remains
stable over time because environmental
conditions cannot change to enable, for
example, maquis or even just garrigue to
establish themselves.
These are only found in a few locations
which feature cracks or clefts in rocks
where soil can accumulate. This gives
rise to a mosaic of fragmented plant
associations which replace each other in
time and space.
Coastal cliffs are therefore characterized
by large surfaces of completely barren
rock alternating with strips of vegetation
which follow the direction of the cracks
and rock layers.
When cliffs have detritus slopes,
vegetation is sparse and covers the
surface irregularly, according to the higher
or lower gradient and stability of the
substrate.
The lithology and geomorphology of
cliffs, their position, type of degradation,
micro-morphology, and possible debris
and soil accumulation can influence plant
colonization.
Cliffs are therefore a series of microhabitats
which are variously influenced by
ecological factors, as shown by the
different plant species.
CLIFF OF SCILLA
3
4
3
1
METAMORPHITES NEAR FAVAZZINA
3
4
7
5
4
3
GRANITE AT BAGNARA
8
6
4
6
2
Types of vegetation on Tyrrhenian
coast in Calabria
1:
2:
3:
4:
5:
Limonietum calabri
Limonietum brutii
Oleo-Euphorbietum dendroidis
Erucastretum virgati
Calicotomo infestae-Ericetum
arboreae
6: Erico arboreae-Myrtetum
communis
7: Erico-Quercetum virgilianae
8: Erico-Quercetum ilicis
55
■ Halophilous cliff vegetation
56
Halophilous vegetation living on cliffs
splashed by seawater is called
Crithmo-limonietum from the name of
its typical plants, mainly sea fennel and
several species of sea lavender.
The distribution of these plants is
determined by coastal morphology.
Halophilous vegetation is more
developed where flanks slope gently
seawards, or along wind-exposed
shores.
Typical species of halophilous
vegetation - sea lavender and sea
fennel - on coastal cliffs are island
garlic (Allium commutatum), sea cliff
Island garlic (Allium commutatum)
carrot, common reichardia, prickly sow
thistle (Sonchus asper), golden samphire (Inula crithmoides) and dusty miller.
This vegetation typically lives on Mediterranean rocky shores, shows an open
and irregular structure, and often contains small, woody species. Most of
these plants are highly specialized, as they are associated with very salty soils.
■ Annual halophilous vegetation
Small cliff terraces sprayed by marine aerosol host associations of annual
species belonging to the class Saginetea maritimae. These grow on thin
detrital substrates, together with other halophilous cliff communities or coastal
garrigue. These small meadows are colonized by sea pearlwort (Sagina
maritima), ryegrass, curved ryegrass (Parapholis incurva) and plantain.
■ Sub-halophilous cliff vegetation
Golden samphire (Inula crithmoides)
Wind blowing over cliff tops is less rich in salt water and aerosol from the sea,
and vegetation is therefore less halophilous, often occurring inland. Gentle
slopes may host maquis of Pistacio Rhamnetalia alaterni, which is replaced on
cliffs by fragmented, chasmophilous plants of the same class.
Areas linking halophilous cliff vegetation with that of maquis or similar, is
characterized by garrigue, and woody plants with salt-tolerant cushions.
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58
Sea lavender
The small, round cushions of sea
lavender characterize rocky shores.
They are annual or perennial herbs,
suffruticous or shrub-shaped, with
woody bases and rosettes of horny
leaves, and shooting scapes
ending with spikes of pale blue
flowers enveloped by papery
bracts.
Their fruit are small achenes.
They colonize coasts all over the
world, but sometimes have
extremely localized distribution.
They are often endemics which, for
their ecological and phytogeographic significance, play the
role of characteristic species of
plant associations.
Almost every rock hosts a particular
species of sea lavender that can
only be found in that spot!
This is due to their type of
reproduction - called apomixis whereby embryos develop without
fertilization, so that populations are
formed of equal individuals, all
slightly different from those of other
populations.
Sea lavender (Limonium sinuatum)
grows in sand, rock, rocky
grassland and brackish lagoons in
Calabria, Sicily and Sardinia.
It has winged branches, sinuate
leaves, flowers with bluish-violet
persistent calyx and whitish-yellow
corolla. It is grown as an
ornamental, and used in dry flower
arrangements.
The persistent calyx has lasting
intense colours. Sea lavender is
usually sold in colours that are
different from their natural ones,
obtained by soaking the plant in
special dyes.
Simonetta Peccenini
The more mature and less halophilous associations which colonize areas far
from the beach, but always sloping, are made up of “spazzaforno”, thymelaea,
Jupiter’s beard, dusty miller, strawflower, etc..
■ Non-halophilous cliff vegetation
Salerno sea lavender (Limonium remotispiculum)
Ligurian sea lavender (Limonium cordatum)
Cliffs host thermophilous, chasmophilous formations of Asplenietalia glandulosi
with glandulose spleenwort, yellow germander, cliff tree-mallow, snapdragon,
phagnalon, red valerian and Oryzopsis coerulescens.
Natural rocky flanks influenced by human intervention are colonized by
associations of the class Parietarietea judaicae, which also grow on walls. The
dominating synanthropic (associated with man’s activities) and nitrophilous
species are white henbane, caper, red valerian, fig (Ficus carica), hoary stock,
common reichardia, snapdragon, navelwort, stock (Erysimum cheiri), wild
chicory, finger fern (Ceterach officinarum) and toadflax (Cymbalaria muralis).
Here, there are also fragments of garrigue, maquis with tree spurge and
oleaster, ampelodesmetum, rockroses, maquis with holm oak or heather and
myrtle, and particularly pine woodland. Although the most extensive Aleppo
pine woodland derives from old reafforestation, communities that colonize
coastal slopes may be considered as natural. Pine mixes with other tree
species, such as buckthorn, lentisk and juniper, forming heliophilous maquis
with a natural structure. Northern
Tyrrhenian, Sardinian and Pantelleria
coasts host spontaneous cluster pine
woodland, which has been greatly
extended for reafforestation purposes.
■ Hygrophilous vegetation
Sea lavender (Limonium sinuatum)
Watercourses, springs and trickling
water, even a few metres from the sea,
give rise to particular conditions which
enable the colonization of a type of
hygrophilous vegetation, Adiantetea. It
is characterized by maidenhair fern
(Adiantum capillus-veneris), brookweed
(Samolus valerandi), liverworts and
mosses, such as bog rush and other
species of rush.
Stock (Erysimum cheiri)
59
■ An overall view of Italian rocky coasts
60
Coastal vegetation on the island of Ponza (Latium)
Let us imagine a voyage round the whole Italian peninsula to examine the
vegetation along rocky coastlines, starting from Liguria, in the west.
Here, the mountains almost reach the coastline, offering shelter against cold
northerly winds and giving rise to the typical mild climate of this region, and
coastal vegetation is limited to a narrow strip.
This vegetation is highly impoverished in comparison with that described
previously. Sometimes, the Crithmo-limonietum (sea fennel and sea lavender
meadows) hosts only one of the typical species, i.e., sea fennel. However,
proceeding upwards and inland on a few promontories, coastal vegetation is
followed by garrigue, Mediterranean maquis, holm oak and pine woodland, or
grassland.
Impressive limestone cliffs are found near Balzi Rossi and Capo Mortola. Here,
between the sea and the Hanbury Botanic Gardens, calcareous rock rich in
nummulites hosts sea fennel, dusty miller, curved ryegrass, and also one of
the many Italian sea lavender species: Limonium cordatum. This attractive
plant, with dense rosettes of spatulate leaves and spikes of tiny pale blue
flowers, is only found on cliffs in Liguria and southern France.
At Finale Ligure, the coast between the promontories of Caprazoppa and
Capo di Vado hosts interesting vegetation, which is similar to that more highly
developed found inland. The limestone substrate, little summer rain, intense,
protracted exposure to the sun, and action of south-westerly (libeccio) and
south-easterly (sirocco) winds create an ideal environment for more
thermophilous and xerophilous Mediterranean plants, e.g., Bethlehem stars
and Savona convolvulus.
The dolomitic cliffs on the Bergeggi promontory host Crithmo-limonietum, with
Ligurian sea lavender, sea fennel and prickly sow thistle near the sea and,
farther inland, dusty miller and stock, which dominate the cliff tops. Where
salty soil rich in animal nitrates can accumulate, are various nitrophilous
species which withstand saltiness, such as spurrey (Spergularia media),
pigweed (Chenopodium album) and scarlet pimpernel (Anagallis arvensis). Cliff
tops still have halophilous vegetation such as sea fennel and dusty miller,
gradually changing into garrigue with pink (Dianthus sylvestris), a relative of
primrose (Coris monspeliensis), “spazzaforno”, and glaucous fescue (Festuca
gracilior), followed by maquis with buckthorn and lentisk.
In eastern Liguria, the mountains are even nearer the coast, which is therefore
higher, rockier and less altered, especially near the promontories of Portofino,
Punta Manara, Punta Baffe, Punta Mesco, along the five villages of the Cinque
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Terre, Portovenere, and between Lerici
and Bocca di Magra.
These cliffs host sea kale with its bluegreen leaves and the hemispheric
shrubs of tree spurge, a plant which
can live in extremely arid and sunny
cliff environments because in summer
it sheds its leaves, i.e., its transpiring
surfaces. The promontory of Portofino,
formed of a layer of marly limestone
surmounted by a thick layer of
conglomerate in its southern part, has
several spurs and ridges plunging into
the sea, which create inlets and small
bays.
Altitude, sunlight, substrate and soil
humidity combine in various ways to
Saxifrage (Saxifraga cochlearis)
give rise to small, grassy meadows
spangled with anemone, primrose, lungwort and orchid, or covered with
precocious Mediterranean flora; steep slopes carpeted with impenetrable
maquis or scented garrigue; and inaccessible vertical flanks colonized by a
few shrubs and slopes, beaten by the wind or scorched by sun and salt.
Shady cliffs on south-western and northern flanks host saxifrage (Saxifraga
cochlearis), which lives only here and on the French Maritime Alps. Where
conglomerate outcrops, near the sea, are interesting halophilous populations
of sea fennel, seashore wild carrot, sea lavender, sea ryegrass and sea bird’sfoot trefoil. Higher cliffs are colonized by spiny spurge, thick-leaved stonecrop
and dwarf palm, of which this is the northernmost location.
At Portovenere, the cliffs host sea fennel, strawflower and wild pink,
especially near narrow ridges where soil is deposited, together with cliff
associations with kale and Porto Venere knapweed (which lives only on this
promontory and on the nearby islands of Palmaria, Tino and Tinetto), and
fragmented formations of tree spurge, juniper, Aleppo pine,
Ampelodesmetum, rockrose, garrigue, and maquis with lentisk, buckthorn,
tree heather and strawberry tree.
A peculiar sea lavender (Limonium multiforme), together with other species of
the Crithmo-limonietum, colonize the Tuscan cliffs of Ardenza, Antignano,
Calafuria, Romito, Castiglioncello, Baratti, Cala Moresca, Punta Ala,
Talamone, Porto Santo Stefano, Port’Ercole and Ansedonia.
Higher cliffs, on the promontory of Piombino, at Uccellina, and Argentario,
host dwarf palm, a relict of warm-loving flora which lives in cracks in rocks
with dusty miller, Jupiter’s beard, Phoenician juniper and tree spurge.
In the Circeo National Park, on the promontory of the same name, is a
calcareous massif composed of crystalline and marly limestone, white flint,
marl, sandstone and scaly clay. Cliffs with caves which sheltered prehistoric
man host cliff vegetation such as the endemic Circe’s knapweed, dwarf palm,
Jupiter’s beard and Phoenician juniper. Cliff bases splashed by seawater are
covered with Crithmo-limonietum like Circe’s sea lavender, sea fennel, sea
bird’s-foot trefoil, seashore wild carrot, Nyman’s prickly sow thistle, cocksfoot,
common reichardia and coastal groundsel.
On the rocky peninsula of Gaeta lives an endemic sea lavender (L.
amynclaeum), which only grows here, at Sperlonga and Terracina.
Proceeding southwards is the high, rocky coast of the Campi Flegrei
(Phlegraean Fields) and the peninsula of Sorrento, which enclose the Gulf of
Naples. Here we may find four different species of sea lavender: on the
volcanic rock of Capri, Posillipo, Gaiola and Sorrento is Limonium johannis,
Aleppo pine on conglomerate cliff on Monte di Portofino (Liguria)
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64
dedicated to the botanist Giovanni Gussone; on the inaccessible calcareous
rocks between Castellamare di Stabia and Vico Equense grows Limonium
tenoreanum, dedicated to the botanist Michele Tenore; at Belvedere, near
Castellamare, Ischia sea lavender (Limonium inarimense) also grew in the past,
but was probably destroyed by human intervention along the Neapolitan
coast; on the limestone rocks of Sorrento is Salerno sea lavender (Limonium
remotispiculum), which is also found near Salerno and in Calabria as far as the
Gulf of Policastro.
The higher cliffs of the peninsula of Sorrento host the endemic Neapolitan
mourning bride (Globularia neapolitana), a crawling plant with beautiful pale
blue heads which form dense clusters on limestone rocks.
High cliffs and steep slopes alternate all along Cilento, the Gulf of Policastro
and the Calabrian coast.
In Cilento, together with Palinuro primrose are other rare cliff species, such as
cliff pink and candytuft, made up of small, hemispheric bushes which bear
corymbs of tiny white flowers throughout winter. Seashores at Marina di
Ascea, Marina di Pisciotta and Caprioli host ephedra-leaved broom, its bare
twigs like those of ephedra, with yellow flowers. This plant may only be found
in the three locations above and on the islands along the Tyrrhenian (Sicily,
Sardinia, Corsica, and the islands making up the Ponza group).
Along the Salento coast is a short, rocky scarp where endemic Apulian sea
lavender (Limonium japygicum) grows. This plant only lives at altitudes ranging
from sea level to 6-8 m, on both steep and gently sloping flanks, from Porto
Cesareo to Otranto.
The high, limestone cliffs at Capo di Leuca host precious flora, such as Apulian
bellflower (Campanula versicolor), an amphi-Adriatic species, i.e., distributed
on both Adriatic shores. Its pale blue flowers with dark centres bloom in late
August. There is also one alyssum species (Alyssum leucadeum), which is
covered with small, yellow flowers in March, and Leuca knapweed, endemic to
this area.
The Adriatic coast is often crowded with people and their numerous artefacts,
so that there are only a few halophilous cliff species. The uniformity of this
coastline is interrupted only by the rocky promontories of Gargano (Apulia)
and Conero (Marches).
Limestone cliff on Capri: cliff vegetation grows only in crevices and soil deposits
Tree spurge and prickly pear along Calabrian coast
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66
On the Gargano promontory, high cliffs
plunging into the sea alternate with
very short stretches of dune beaches.
This promontory is similar in its
geological, environmental, floral and
faunal characteristics to the Dalmatian
coast, with which it is associated.
The coastline between Mattinata and
Peschici is a series of high limestone
cliffs with bays, inlets, small beaches,
monolithic rocks and grottoes. Here
live Phoenician juniper, Jupiter’s beard
and, further down, where the shore is
splashed by seawater, species of the
Crithmo-limonietum.
Sunny cliffs host mullein-leaf samphire
(Inula verbascifolia), an amphi-Adriatic
Mullein-leaf samphire (Inula verbascifolia)
species, which is completely covered
by white, woolly down. It has yellow flowers in heads surrounded by white
scales.
On rocks and walls in more shaded areas at Peschici, Rodi Garganico,
Cagnano, Monte S. Angelo and Mattinata grows the beautiful Adria bellflower
(Campanula garganica), endemic to this promontory. Its rosettes of crenateserrated leaves bear on their axils stalks rich in star-shaped corollas of pale
blue-violet or white flowers.
Monte Conero is composed of high cliffs of various rock types. Marly
sandstone cliffs, formed of layers of clay and subject to frequent landslides,
mainly host Plinius’ reed (Arundo pliniana), which consolidates slopes by
covering them with a dense net of rhizomes and roots.
Calcareous rocks near the sea or debris with the same ecological position
have typical halophilous vegetation with sea fennel, common reichardia, and
wild kale.
Debris falling from higher rocky flanks is colonized by white-flower cephalaria
(Cephalaria leucantha), bedstraw (Galium lucidum), wild madder (Rubia
peregrina) and, if splashed by water, sea fennel. A few rocky flanks have tree
spurge and hoary stock; consolidated debris contains buckthorn
(Ampelodesmus mauritanicus), broom (Spartium junceum) and shrubby
scorpion vetch (Coronilla valentina). The coast between Duino and the border
with Slovenia is high and rocky.
Spontaneous succulent plants
Coasts host many plants of the
mesembryanthemum, stonecrop and
saxifrage families, which feature
xerophytic and halophytic adaptations
which enable them to live in these
environments, generally shunned by
other species.
The most conspicuous are the
Crassulaceae, among which are
perennial stonecrops, such as orpine
(Sedum telephium), with purple flowers,
great stonecrop (Sedum maximum)
with greenish-white flowers, Nice
stonecrop (Sedum sediforme), white
stonecrop (Sedum anopetalum) with
whitish flowers, cliff stonecrop (Sedum
rupestre), Sedum tenuifolium with
yellow flowers, and annual stonecrops
(Sedum stellatum, S. litoreum, S.
caespitosum, S. andegavense, S.
caeruleum). Annual stonecrops are very
ephemeral, and in April-May their tiny
flowers cover the arid cliff cracks in
which these plants live, set fruit and dry
up in early summer.
Anjou and azure stonecrop are
calciphobes, and therefore live on silicic
walls or acid red soil, whereas bushy
stonecrop lives on limestone cliffs.
Three species of navelwort (Umbilicus
rupestris, U. erectus, U. horizontalis)
live on Italian coasts on damp cliffs
and old walls with some water trickling
down them. The first is the most
common and the second, reniform
navelwort, the rarest. This is an eastern
Mediterranean species which, in Italy,
only lives in Gargano and Sila. All three
navelworts have round, fleshy, shieldshaped leaves, arranged around
scapes bearing clusters of erect,
yellow flowers on their tips. The
flowers may be spreading or hanging
according to species.
Simonetta Peccenini
Saxifragaceae typically live in the
mountains, although Saxifraga
cochlearis, endemic to the Maritime
Alps, also grows on conglomerate cliffs
facing north-west on the Portofino
promontory. Its small, teaspoonshaped leaves (as its Latin name
suggests) have edges dotted with
white. These are calcareous crusts due
to the discharge and evaporation of
calcium carbonatic water from their
pores, called hydathodes.
Of the Aizoaceae (mesembryanthemum
family) are Hottentot figs and two rare
species of ice plant
(Mesembryanthemum nodiflorum, M.
crystallinum). These small, halophytic
annuals have creeping stalks and
fleshy leaves, linear in the former and
oval in the latter. They have a peculiar
distribution, being found in the
Mediterranean, South Africa, and the
latter also in Australia.
Cliff stonecrop (Sedum rupestre)
Navelwort (Umbilicus rupestris)
67
On the limestone cliffs of Trieste, the Crithmo-limonietum is even poorer in
typical species, which are sometimes restricted to sea fennel alone. However,
there are other interesting cliff species, such as the endemic Karst knapweed,
which may be found up to 50 m from sea level in Duino and Sistiana. Here also
are the feathery, cob-like flowers of Venetian sumac (Cotinus coggygria).
In Sicily, many cliff species are found in the Riserva dello Zingaro (Trapani). The
Crithmo-limonietum contains Limonium flagellare, sea fennel, ryegrass, sea
cliff carrot, Spanish chicory, grey bird’s-foot trefoil, common reichardia, golden
samphire and stock; cliff associations of Dianthion rupicolae with cliff pink,
Todaro’s sea lavender (Limonium todaroanum), Boccone’s moon carrot and
candytuft; and Lomelosio creticae-Centaureetum ucriae with cliff strawflower,
Ucria knapweed and Turkish convolvulus.
Limestone or granite cliffs in Sardinia contain Crithmo-limonietum with various
endemic species of sea lavender, woody frankenia and camphor-scented sea
heath. Cliff tops host associations of endemic species such as Boccone’s
moon carrot and Sardinian kale or, in the Nurra region, fragmented garrigue
with spiny knapweed.
68
The rocky spur of Monte Conero (Marches) interrupts the long series of sandy Adriatic beaches
Deep inlets along rocky coastline in hard, resistent granite (northern Sardinia)
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71
Terrestral fauna
GIUSEPPE CARPANETO
■ Fauna: invertebrates
The windiness, saltiness and high
summer temperatures typical of rocky
shores make life impossible for small
animals, incapable of efficient thermoregulation and lacking suitable
protection against loss of water from
their tissues. This is why there are only
a few terrestrial invertebrates which
permanently live in these environments
where there is little or no soil. The
largest taxonomic groups comprising
species associated with cliff phytocenoses are gastropod molluscs and
arthropods.
Rock pools along Sicilian coastline
Molluscs. Gastropod molluscs generally spend the day in cracks or hollows in
rocks and move during the night, to feed on plants. Obviously, they are more
numerous where vegetation is thicker. A few species are found under deposits
of algae and sea plants carried on to rocks by storms.
Among the most frequent marine species found along cliffs, in areas splashed
by the sea, are those of the genera Patella and Littorina (periwinkle). Species
typical of salty waters are Truncatella subcylindrica, Paludinella littorina and
Caracollina lenticula. The first is found along the Mediterranean and Atlantic
coasts of Europe and Africa; the second along Mediterranean coasts and
Macaronesia; the third on the western Mediterranean.
Molluscs which are often found on cliffs are clausiliids of the genera
Lampedusa and Muticaria, endemic to Sicily and nearby islands. These small
snails have elongated, spindle-shaped shells, and live in cracks in limestone
rocks. Other clausiliids living in rocky environments are species of the genus
Siciliaria, in the Balkans, Italy and Sicily. More frequent are species of the genus
Peregrine (Falco peregrinus) on cliffs near Trieste (Friuli Venezia Giulia)
72
Papillifera, which belong to the same
family and are associated with the
same habitats.
One of the most typical animals found
on cliffs is Papillifera solida, a western
Mediterranean
species.
Another
important species, although less
widespread, is Marmorana saxetana,
endemic to the Tyrrhenian. Rocky
coasts also host many terrestrial
gastropods, which are not typical of
these
environments
but
are
Littorina (Melaraphe) neritoides
euryoecious, i.e., widespread in various
types of habitats, and generally
associated with cliffs. All these species make up large populations and are
therefore important sources of food for many animals, such as arthropod
predators, lizards and migrant birds resting along the shores.
Arachnids. Among arthropods are many arachnid species, especially spiders,
harvestmen and mites. A few species of spiders spin their webs on plants or
across rock hollows hoping to catch small insects. A few species of spiders
spin their webs on plants or across rock hollows. The most widespread webspinners in coastal environments are dictynids, orb spiders and sheet-web
weavers. Only orb spiders weave wide, regular webs between empty spaces in
the vegetation. Dictynids (genera Argenna, Lathys) and sheet-web weavers
spin irregular webs at the tips of dry plants or between cavities in the ground.
Some dwarf spiders are even carried by the wind, which blows them on their
tiny “flying mats”, thus enabling them to colonize islands.
Several species of jumping spiders (e.g., those of the genera Marpissa,
Euophrys, Sitticus) move swiftly on the ground, actively searching forˇ prey, on
which they pounce with sudden leaps. Other species, like crab spiders, stalk
their prey on cliff plants, waiting until flying insects mistake them for petals.
Many species of spiders, such as gnaphosids, sac spiders and liocranids are
nocturnal and spend the day in their cocoons, from which they emerge after
sunset. This is the case of the tiny gnaphosid Haplodrassus minor, the sac
spider Clubiona frisia and the liocranid Agroeca lusatica, typical of coastal
environments.
Spiders are often confused with harvestmen, an arachnid order whose
members have compact, generally unsegmented bodies. Metaphalangium
propinquum, a widespread Mediterranean species, lives in warm, arid
environments on all Italian islands.
Sedimentary cliffs host various families
of mites, which wander in search of
lichen, insect eggs and tiny animals. A
few species are parasitic on the skin of
lizards, on which they form large
patches. Those of the halacarid family
are aquatic and live in both cliff pools
and coastal water. In Italian fauna, they
include about 50 species belonging to
Ligia italica
17 genera.
A few false scorpions also live on rocky
shores, e.g., Neobisium maritimum, and those of the genus Roncus even live
on rocks near the water.
Crustaceans. Isopods, better known as woodlice, are the only crustaceans
adapted to terrestrial environments and may be found in cracks in rocks, where
they hide during the day. Here are various species of armadillidiids, the armourlike tegument of which makes them resistant to xero-thermal conditions, as it
prevents them from losing water from their tissues. Some of these species are
endemic to the Italian islands, such as Armadillidium pseudassimile on Capraia,
A. oglasae of Montecristo and A. tyrrhenicum on Giglio. However, the most
typical species is undoubtedly Ligia italica, which may be seen even during
daytime, scuttling on rocks, hiding in cracks, or even sheltering in water. During
their reproductive period, the females plunge into the sea, where their eggs are
laid and hatch.
Centipedes and millipedes. Species of centipedes and millipedes are not
exclusive inhabitants of rocky coasts. In this environment, the two classes are
generally associated with cliff habitats. For instance, a common centipede is
Scutigera cleoptrata, frequently also found in houses. A swift predator, it has a
short body and very long legs, the number of which is smaller than that of other
members of this class.
Among millipedes are various species of julids, typical millipedes with
cylindrical bodies. They are slow, nocturnal detrivores, which spend the day in
cracks in rocks. Cliffs near the sea, splashed by seawater and covered at high
tide, house some very characteristic specimens.
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Fauna in cliff pools
Cliff pools are very interesting
microhabitats. These small reservoirs in
the rock may contain either seawater or
rain. The former are filled during storms,
and the latter collect water during
Mediterranean spring or autumn. Their
closeness to the sea, and the rainfall,
seasonality, depth and extension of
these hollows all give rise to a complex
series of situations according to
saltiness. During summer, intense
exposure to the sun increases the
evaporation of seawater in the pools,
and they therefore become saltier. This
salt precipitates, and later rainfall
decreases the saltiness, giving rise to
brackish or even freshwater habitats.
Cliff pools host marine or brackishwater planktonic biocenoses made up
of flagellate protists, rotifers, small
crustaceans (isopods, amphipods,
copepods, etc.) and insects. Typical are
the hydraenid beetles of the genus
Ochthebius. The adults of these tiny,
black, shimmering bronze insects
(Ochthebius quadricollis, O. subinteger)
are about 2 mm long. They are
phytophagous and detrivorous: they
feed on algae and vegetal remains in
the pools. The adults slowly tread the
bottom and walls of pools, but must
emerge to breathe. They store water in
a very curious way: they detach
themselves from the bottom, turn
upside-down, rise vertically to the
surface and adhere to the underside of
the surface with their legs. The dense,
short hairs covering their bellies touch
the air and capture it, forming a silvery
film. Once sufficient air is stored, the
insects continue their upside-down
walk as far as the pool walls, where
they start descending again. Their
larvae live on the bottom and feed on
Giuseppe Carpaneto
organic matter. In summer, when
evaporation is intense and salt
concentration too high, these beetles
fly away in search of pools that suit
them better.
A few species of dragonflies may also
visit pools, particularly those containing
freshwater. Eggs are laid in the water
and voracious larvae are born, which
feed on any tiny animal colonizing these
microhabitats.
When stalking their prey, dragonfly
larvae move slowly on the bottom,
whereas aquatic heteropterans (water
bugs), especially water striders, water
boatmen and back swimmers, move
swiftly. Water striders scuttle on the
water surface; water boatmen and back
swimmers are very skilful swimmers.
These bugs catch small invertebrates
and suck their body fluids through the
powerful piercing suckers in their
mouths. In a few water strider species,
colonization is carried out by
macropterous (long-winged) individuals,
which reproduce forming populations
air
of brachypterous (small-winged)
specimens. Other predators in pools are
true water beetles, particularly those of
the genera Agabus, Coelambus and
Hydroporus. Whirligig beetles twirl on
the water surface.
Among dipterans are non-biting midges,
gnats and mosquitoes. Mosquitoes can
adapt to life in salty water, although
most of them prefer freshwater pools
with rainwater.
These micro-environments, which are
isolated in the rock and without fish, are
ideal for the development of
mosquitoes, which can reproduce
without having their numbers controlled
by predators.
The only mosquitoes specializing in life
in hot, salty pools are Aedes mariae and
A. zammitii. These two species, the
former particularly, are very aggressive
towards man. They can fly into houses
and bite, both during the day and at
night, thus constituting a problem for
summer tourists.
Other species living in salty or brackish
Patella ferruginea
water are Culex modestus, Culiseta
litorea, Anopheles sacharovi, Aedes
detritus, etc., although they are not
typical of coastal pools.
Only in particular situations, large pools
containing rain and sheltered by
hanging rocks are inhabited by
amphibians (green toad, tree frog, green
frog), which find here ideal living
conditions. But water temperature must
not be too high and the area must be
protected from predators - requirements
difficult to meet due to the lack of
vegetation.
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The genus Thalassisobates includes tiny millipedes specializing in life in these
habitats, such as Thalassisobates adriaticus, generally found only a few
metres from the sea. Among centipedes are species living under algal debris
and the remains of Posidonia, on various types of shores: Hydroschendyla
submarina, Geophilus poseidonis and G. fucorum are found along both sandy
and rocky coasts.
Insects. Very few species of insects live near the sea, practically along the
shoreline. In the intertidal zone, in addition to several species of springtails,
which are often associated with cliff pools, one of the most exclusive species
is the bristletail Petrobius maritimus, which lives on rocks splashed by water.
This delicate hexapod may be seen running jerkily along rocks and hiding in
cracks.
Where pebbles and coarse sand form small deposits between rocks, we find
the cricket Pseudomogoplistes squamiger, an orthopteran species exclusive
to this environment throughout the Mediterranean. The earwig Anisolabis
maritima also lives along the coast, especially where algae and debris are
washed ashore.
Anisolabis maritima
The role of predators is played by
carabid beetles, such as the metallic
blue Ocydromus (Omoperyphus)
steinbuehleri, typical of rocky shores
and cliff pools. It lives in small areas
along the Mediterranean coast. In Italy,
it has only been collected in a few
isolated places, along both Tyrrhenian
and Adriatic shores.
Cricket Pseudomogoplistes squamiger
Another halobious (associated with
coastlines) carabid is Lymnaeum
nigropiceum, which lives along
European Atlantic coasts and the
Mediterranean, as far as the Black Sea.
It is found in the intertidal zone under
rocks and in cracks at the foot of cliffs.
In Italy, it was mostly found in Sardinia,
on some Tyrrhenian islands and in the
northern Adriatic. Even rarer is
Lymnaeum abeillei, only found in a few
Ground beetle Limnaeum nigropiceum
sites in southern France, Corsica,
Liguria, Latium and Abruzzi.
However, most insects living along
rocky shores are associated with plant
communities, such as the Crithmolimonietum of rocks and the
Mediterranean maquis, which thickens
proceeding inland.
Among
phytophagous
species
associated with rocky coasts is the
Ground beetle Ocydromus (Omoperyphus)
brown long-horned beetle Parmena
steinbuehleri
pubescens, which is about 1 cm long
and parasitic on the umbellifer Crithmum maritimum, a guide-species of the
Crithmo-limonietum.
Few phytophagous insects are exclusive to rocky coasts, as they also live
inland, in the evergreen Mediterranean maquis, deciduous woodland and
pastureland farther from the coast. Together with phytophagous insects are
other more or less specialized or euryoecious predators, i.e., indifferent to the
type of environment.
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■ Fauna: vertebrates
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Amphibians and reptiles. Amphibians are seldom seen on rocky coasts,
unless they live in salty or freshwater pools in rocks. Species which may inhabit
these environments are green toad (Bufo viridis), tree toad (Hyla intermedia and
H. sarda) and frogs of the esculenta group (Rana hispanica, R. bergeri).
The presence of amphibians implies that of their predators, i.e., reptiles, such
as grass snake (Natrix natrix) and viper snake, especially near large freshwater
pools. A more frequent snake along rocky shores is rat snake or green and
yellow coluber (Hierophis viridiflavus), which crawls on steep slopes in search
of birds’ eggs and nests. However, its usual prey are lizards, which are the
most frequent and numerous reptiles in these environments.
Rocky cliffs near Trieste still house cat snake (Telescopus fallax), which moves
as far as the shoreline hunting for lizards. Various widespread species belong to
the lizard family and live both inland and along rocky coasts, such as common
wall lizard (Podarcis muralis) and wall lizard (Podarcis sicula). These two
species constitute morphologically differing populations on the islands and
therefore, in the past, many geographical subspecies were described
according to their external features (colour, size, shape of body and scales).
Viperine snake (Natrix maura)
Rat snake or green and yellow coluber (Hierophis viridiflavus)
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A few of these subspecies are clearly differentiated, such as the blue wall lizard
(Podarcis sicula cerulea), which lives on the plunging cliffs of the “faraglioni” of
Capri. It has a typical dark blue back and deep turquoise belly. Another
beautiful type of lizard, as a separate subspecies, is Isola Bella wall lizard
(Podarcis sicula medemi), with a brick-red belly. It is found on the tiny island of
the same name, near Taormina, Sicily. The rocky coastline of Duino-Aurisina
(Trieste) hosts Melisello lizard (Podarcis melisellensis), which sometimes
reaches the shoreline.
As regards lizards, it is difficult to separate the fauna of rocky coasts from that
living on islands, because many endemic subspecies live exclusively on small
islands and archipelagos.
Among wall lizards are Podarcis sicula aemiliani (Scogli di Apani, near Brindisi),
P. s. trischittai (Isolotto Bottaro, Aeolian Islands), P. s. calabresiae
(Montecristo), P. s. klemmeri (Licosa, in the Gulf of Salerno), P. s. lanzai
(Isolotto Gavi, islands of the Ponza group), P. s. liscabiancae (Isolotto Lisca
Bianca, Aeolian Islands), P. s. pasquinii (Scoglio Cappello, Ponza group) and P.
s. roberti (Formica Grande di Grosseto, Tuscany). Among wall lizards are
Podarcis muralis beccarii (Isolotto Porto di Ercole, Tuscany), P. m. marcuccii
(Isolotto Argentarola, Tuscany), P. m. muellerlorenzii (Isolotto La Scola,
Tuscany) and P. m. tinettoi (Isolotto Tinetto, eastern Liguria). Research on the
thermoregulation of the Argentarola lizards, which are dark in colour, has
shown that, after these animals have basked in the sun and started moving,
their body temperature is higher than that of the normal spotted population of
nearby Monte Argentario.
Sardinia hosts large numbers of Tyrrhenian lizard (Podarcis tiliguerta) and other,
more localized species like Bedriaga’s rock lizard (Archaeolacerta bedriagae)
which, in the past, was believed to be associated with rocky, mountain
environments in Sardinia, such as Gennargentu and Monte Limbara, where
these animals may be found up to 1800 m. Later, coastal and even insular
populations were discovered, e.g., on Folaca, a small granitic island of only
3700 sqm and only 11 m in altitude. On this tiny island, Bedriaga’s rock lizard
lives alone, probably due to the absence of competitors.
In Sicily we find wall lizard (P. sicula) and Italian wall lizard (P. wagleriana), living
in almost all environments, although the latter species seems to be associated
with meadowland rather than rocky substrates.
Instead, Aeolian wall lizard (Podarcis raffonei) is typical of the rocky habitats of
a few small islands of the Aeolian archipelago, such as Vulcano (restricted to
the Vulcanello peninsula and nearby rocks), Strombolicchio, Scoglio Faraglione
Wall lizard (Podarcis sicula)
Bedriaga’s lizard (Archaeolacerta bedriagae)
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