I TA L I A N H A B I TAT S
Sand dunes and beaches
4
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 commitee
Aldo Cosentino · Alessandro La Posta · Carlo Morandini · Giuseppe Muscio
“Sand dunes and beaches · Environments between land and sea”
edited by Sandro Ruffo
Texts
Paolo Audisio · Giuseppe Muscio · Sandro Pignatti · Margherita Solari
In collaboration with
Alessio De Biase · Luca Lapini · Lorenzo Chelazzi e Isabella Colombini (Tipology of habitats)
English translation
Elena Calandruccio · Gabriel Walton
Illustrations
Roberto Zanella
except for 67, 73 (Niccolò Falchi) and 102 (Franco Mason)
Graphic design
Furio Colman
Sand dunes and beaches
Environments between land and sea
Photographs
Archive Museo Friulano di Storia Naturale (Ettore Tomasi) 49/2 · Paolo Audisio 6, 14, 20, 30, 31, 32, 33,
37, 40/1, 40/2, 41, 42, 43, 44/1, 44/2, 44/3, 51, 52/2, 58, 60, 61, 63, 64, 69, 72, 76/1, 79, 81/1, 81/2,
83/1, 83/2, 84, 92/1, 92/2, 94/1, 95/1, 97, 98, 106, 114, 118, 124, 125, 127, 129, 131, 133, 135, 137,
139, 142/1, 142/2 · Enrico Benussi 108/2 · Roberto Bigai 52/1, 140 · Maurizio Biondi 142/3 ·
Giuseppe Carpaneto 48, 86 · Achille Casale 107, 119 · Compagnia Generale Ripreseaeree 10, 18 ·
Ulderica Da Pozzo 112 · Dario Ersetti 34 · Gabriele Fiumi 94/2 · Paolo Fontana 80, 95/2, 96, 103 ·
Istituto Geografico Militare 19 · Luca Lapini 111 · Paolo Maltzeff 76/2, 78, 88, 91, 93/1, 101 ·
Ugo Mellone 7, 9, 128 · Michele Mendi 110 · Giuseppe Muscio 16, 49/1, 145 ·
Roberto Parodi 53, 109/1, 109/2 · Sandro Pignatti 38, 116/1, 116/2 · Paola Sergo 56 ·
Margherita Solari 28, 36, 47 ·Antonio Todaro 70, 71 · Elido Turco 123 ·
Augusto Vigna Taglianti 74, 75, 90, 93/2, 108/1, 142/4 · Roberto Zucchini 104
© 2003 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 11 5
Cover photo: footprints of a wild rabbit (photo by Paolo Audisio)
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
Paolo Audisio
Geological and geomorphological aspects . . . . . . . . . . . . . . . . . . . . . . . . 11
Paolo Audisio · Giuseppe Muscio
1
Caves and
karstic
phenomena
2
Springs and
spring
watercourses
3
Woodlands
of the Po
Plain
4
Sand dunes
and beaches
5
Mountain
streams
Paleogeography and biogeography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Paolo Audisio · Giuseppe Muscio · Sandro Pignatti
Beach vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Sandro Pignatti
Sandy shores and their animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Paolo Audisio
6
The
Mediterranean
maquis
7
Sea cliffs and
rocky
coastlines
8
Brackish
coastal lakes
9
Mountain
peat-bogs
10
Realms of
snow and ice
Problems of conservation and management . . . . . . . . . . . . . . . . . . . . . . 113
Paolo Audisio · Giuseppe Muscio · Sandro Pignatti
Suggestions for teaching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Margherita Solari
Select bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
11
Pools,
ponds and
marshland
12
Arid
meadows
13
Rocky slopes
and screes
14
High-altitude
lakes
15
Beech
forests of the
Appennines
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
List of species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
5
Introduction
PAOLO AUDISIO
Shore and sub-shore beaches and
sand dunes, together with damp, siltysandy environments of shore dunes
usually associated with them, are one
of the most vulnerable and seriously
endangered ecosystems in the world.
Until a few decades ago, in the
Mediterranean and in Italy, these
peculiar environments had eluded
direct destruction and severe damage
because, throughout the centuries,
man had colonized only areas near
Vegetation on a sand dune
mouths of rivers and sheltered bays.
Unfortunately, in recent years, these
ecosystems have been variously disturbed and damaged by man’s
intervention: pollution of coastal waters, urbanization, fires, tourism, agriculture,
thermo-electric power stations and industry, port activities and removal of
sands for building purposes.
Another potential, future danger is the feared rise in sea level (associated with
the scientifically documented rise in mean annual temperature worldwide),
which would further jeopardize these fragile and little-extended marine
environments, despite the dynamic structure - i.e. the considerable resilience,
or ability to recover;, of their biotic communities. Even intense coastal erosion
may locally reduce the size of these habitats, although erosion and
accumulation are natural evolutions of beach-dune environments.
These events, combined with the growing exploitation of shores by man, have
fragmented these habitats, which must now be monitored and safeguarded.
Deeper knowledge of plant and animal communities of beach and sandy
shore dunes, of hydrogeological and geomorphological dynamics which
determine their formation and evolution, are therefore essential for environmental protection, both at national and European Community levels. The
spread of knowledge is essential in making everybody aware that these
Mouth of river Irminio (Sicily): a beach stretch of good environmental quality
7
8
ecosystems must be protected. Unlike other terrestrial habitats, beach and
shore sand-dune ecosystems have simple plant and animal communities and
a very few species, due to their peculiar environmental and microclimatic conditions and restricted extent. However, these environments have selected
peculiar and specialized plant and animal elements, due to the very presence
of extremely limiting abiotic parameters and generalized conditions of severe
environmental stress.
This has given rise to high numbers of specialized psammophilous organisms
(exclusively associated with brackish and sandy shore environments) in both
plant communities and animal ones (particularly arthropods), in comparison
with the remaining species which constitute biotic communities.
The analysis of animal and plant communities in dunes and dune heath evidences frequent overlapping of floral components and faunal ones, especially
xero-thermophilous, psammophilous or hygrophilous components which do
not only live in shore and surrounding environments (Mediterranean or subMediterranean maquis and garrigue), but also in steppe-like meadows, moors,
brackish-sandy terrestrial environments near rivers and lakes, or aeolian
rocks. Particularly in central-southern Italy and its islands, beaches, dunes
and dune heath are “hedges” for many terrestrial organisms (especially coastal
ones, but not only) which are passively or almost passively carried on sea
stretches by currents, winds and floods during storms and exceptional meteorological phenomena.
The naturalistic value of these rare coastal communities lies in the co-existence of various elements of different biogeographic origin which share high
levels of trophic specialization. They are exclusively found in these areas, and
are therefore good “indicators” of the general biological value of the ecosystems in which they still live.
This book analyses the main characteristics of Italian sand dunes and sand
shores from the geomorphological, floristic, vegetational and faunistic points
of view, and their very different types. Differences depend on the great latitudinal and bioclimatic extent of Italy and its islands, and on the influence of various, completely different biogeographical and historical factors which determine animal and plant populations.
This book does not deal with the large numbers of heterogeneous, typically
marine organisms which occasionally or regularly visit sandy shores as stranded remains or masses of organic matter, unless these remains are typically
used by sand animals as food or shelter. In the same way, it does not describe
typical inland organisms which are occasionally found on beaches and sand
dunes, and eurytopic hygrophilous organisms (associated with damp environ-
9
Passage from sandy shore to Mediterranean maquis
ments of various vegetation), which are not exclusive to damp, sandy shore
environments (salicornia, jonquils, coastal reeds beds etc.). Obviously, the
large numbers of birds which live or shelter, particularly during the winter, on
beaches, mouths of rivers, marshes and interdunal brackish lagoons, or all the
aquatic communities which live in those areas, are not studied in this book.
The complex mesopsammon of sand and gravel under the beach surface (i.e.,
all those microscopic, unusual, specialized animals which live in large numbers in interstices between sand grains), is not treated here, because they are
exclusively with aquatic environments, although it is linked with land and sea.
Those who are interested in this peculiar and fascinating “miniature world”
may find information in the box devoted to mesopsammon (pp. 70-71).
This book treats the most characteristic and peculiar animals and plants which
spend all their life, or most of their lifecycle, in these mainly terrestrial environments in Italy, where they constitute natural populations. It also discusses protection and management problems regarding this ecosystem, its communities
and single species.
Geological and geomorphological aspects
PAOLO AUDISIO · GIUSEPPE MUSCIO
Beaches are narrow strips of accumulated sand between sea and land. They
are extremely dynamic areas, where balance is determined by various factors
which may be divided into two groups: passive (topography of the area, material) and active (winds, waves, sea currents, tides, river supply, activity of
organisms, including man!).
Sand beaches are composed of incoherent rock sediments of alluvial and
marine origin, the particle size of which is fine, but not very fine (sand is conventionally made up of fragments the mean inferior diameter of which is 2 mm;
when grains are much smaller and between 0.06-0.004 mm it is called silt; if
grains are even smaller, it is clay; grains exceeding 2 mm form gravel).
The Italian word spiaggia (beach) comes from piaggia, which derives from the
Latin plaga meaning “flat extension”, and from the Greek plagio meaning
“lateral” and its verb piaggiare (to sail along the coast), with the prefix sidentifying a lasting action. The word dune defines the narrow, long, shore or
sub-shore area which usually stretches parallel with the coastline and is
characterized by low rises (in Italy, between 1.5-12 m, with a few exceptions in
Sardinia), constituted by wind-deposited incoherent sediments. Sand dunes
are made up of more or less incoherent sand, according to its age and vegetal
presence, the upper layers of which are compacted. The word dune comes
from the Middle Dutch dune which means “small rise, hill, high ground”.
Most of the longest, stabler and more complex (therefore more significant in
biocenotic terms) sand-dune systems, form where shore stretches are low and
marked by plains landwards and shallow depths seawards.
■ Beach structure
Technically, beaches are shores made up of loose material which moves with
the waves, and are produced by constructive phases, although some areas
may be eroded in certain periods.
Beaches have variable stretches: if they are associated with rocky coasts, they
are only narrow strips of loose sediments along which emerging rocks are not
splashed by the sea, and they may develop into small bays. Near deltas or
Dispersion of sediments at mouth of river Tagliamento (Friuli Venezia Giulia)
11
12
Geomorphological description of a beach-dune system
13
storm berm crest
ordinary berm crest
waterline
waterline hollow
dune
storm berm
foot of dune
dune
ordinary berm
bar
interdunal lagoon
exposed beach
estuaries, beaches may be so large as to block part of the system. But the
best place for the formation of large dune systems is near broad plains.
Conventionally, beaches stretch landwards as far as the limit of storming
waves, and seawards as far as a mean depth calculated as half the mean
wave length during sea-storms. The movement of sand particles caused by
waves at lower depths is considered negligible.
This large stretch of coast may be divided into three sections, proceeding seawards: exposed beach (or sandy shore), intertidal beach and submarine beach.
Exposed beach is the emerged area included between the limit of storming
swash and the so-called ordinary berm, i.e., the clearly visible ridge modelled
by breakers (but also erosion and accumulation) inside the limit of the waterline. Waterline is that beach stretch which slopes seawards and on which
swash and backwash alternate (backwash is the return of water which is
pushed ashore by swash). There are high- and low-tide waterlines, with a vertical variation between the two (i.e., imaginary lines which join points of the
beach splashed by swash) of about 30 cm in Italian seas. Inside the exposed
beach, there is another ridge called storm berm, which indicates the maximum
level reached by swash during the last sea-storm. Storm berms form after violent storms which alter the beach morphology. They are usually preceded by a
small, sudden slope called beach scarp.
Intertidal beaches are areas between the mean levels of high and low tide.
Proceeding landwards, their first part is composed of the high-water line.
bar
submerged beach
Normally, the lower stretch, which indicates the limit of sand carried by backwash during high tide, is another ridge, which limits the waterline seawards.
Beyond this ridge is the so-called low-tide terrace which is often characterized by bars and banks (small ridges organized longitudinally, parallel or subparallel to the shore), which are formed in the temporarily submerged beach
by waves or local currents. The upper and lower limits of the waterline are
obviously variable and depend on the height of breakers and tide levels.
Submarine beach is the seaward portion of a beach, between the mean level
of low tide and mean depth considered to be half the mean wavelength during
sea-storms. Also in submarine beaches there are more or less evident bars or
banks preceded by small hollows called troughs.
Beaches are therefore variably inclined slopes where the energy of waves
dampens. Normally, slope gradient increases if the incoherent material carried
and washed away is coarser: this phenomenon is due to hydrodynamics, as
the gradient of the waterline is determined by the alternating movement of
incoming material pushed by swash and out-going material carried away by
backwash. Although kinetic energy is equal, fine material like sand can be
carried downwards on gentle inclinations, and coarser material such as gravel
or pebbles needs higher gradients. Remodelling and re-adaptation of beach
waterlines is always determined by a temporary, dynamic balance.
Exposed beaches, where sand is dry, are affected by wind which creates and
models dunes and sand-dune systems.
14
■ Dynamics, formation and erosion
of sand beaches
The formation and evolution of sand
beaches are closely linked with various
factors, such as debris supply, conformation and geological origin of nearby
coasts, transportation and accumulation of debris by waves and currents.
Evident signs of erosion on a Sicilian beach
The main agents in the modelling of
beaches are waves and currents and,
especially in the exposed portion of the beach, wind is also important, as it is
the chief cause of wave formation. Tides are not as important, although they
often shape the long stretch called intertidal beach. Debris supply is fostered
by nearby rivers and watercourses which efficiently carry sand, mud and alluvial debris of various sizes. Debris may also derive from the contemporaneous
erosion of nearby coasts and it is carried by the homogenizing and regulating
action of waves, which smooth coastal protrusions by washing away material
and depositing it on the sides of the protrusion itself, usually in sheltered bays.
Sand may be eroded from depths near the coast.
When beaches are near river mouths, large quantities of debris accumulate
along nearby coasts. In large accumulation areas, debris is organized according to its weight and energy necessary to carry it. If the sea bed is steeply
inclined, gravity pushes debris offshore, where it cannot be washed ashore
again. If the sea bed is gently inclined, oblique waves form offshore, and only
weak waves reach the coast, which is therefore marshy, with clay and silt. In
other areas, accumulation is due to the combined transport of material to the
waterline and is called longitudinal transport i.e., parallel to the shore.
In order to understand how debris is carried by waves, dynamics and kinetics
of wave motion must be analysed. As is well-known, waves are usually
produced by wind, which conveys part of its energy to surface water and
pushes it in a horizontal wave motion, according to direction of propagation
perpendicular to wave crests. Near shores, the gradient and faces of sea beds
and coasts may change the direction, shape and energy of waves. Particularly
important are waves produced when the water carried by water crests is faster
than the speed of propagation of the wave itself and fall forming beach
breakers, which use up all their kinetic energy to reach the shore as swash. At
this point, gravity makes swash recede as backwash. This situation undergoes
seasonal variations: during intense winter storms, breakers are stronger and
part of the sand which makes up the waterline may be drifted away by wave
motion to form bars in submarine beaches, or be carried offshore.
The opposite occurs in summer, when weak waves carry all the material back
to the coastline. Sand beaches are, therefore, considerably different throughout the year: in summer, they are wider because there is more sand; in winter,
all the material accumulates in the submerged portion as bars.
■ Structure of a shore sand dune
Sand dunes are variously shaped mounds of windblown sand. We have already
described the causes for the formation of exposed beaches which the wind
shapes in shore sand dunes by carrying sand deposited by waves and storms.
Shore sand dunes, except for their position, do not differ greatly from other
types of dunes which form inland, in continental areas where wind deeply
erodes substrates. There are various types of sand dunes, according to their
orientation and organization with regard to wind direction. Shore sand dunes
are usually transverse dunes i.e., they face the wind; if they form behind
beaches and crescent-shaped sand bays, they are called parabolic dunes.
Most shore dunes are transversal, the upwind face of which (usually the seaward one) is less steep than the lee (usually facing inland). Sand climbs the
windward face as saltating or bouncing grains until it reaches the crest, where
gravity makes grains bounce down the lee. Shore dunes may have variably
sinuous crests produced by winds blowing in different or opposite directions.
The difference between shore dunes and mobile continental dunes lies in the
vegetation of the former, which has a “hedging” effect, preventing dunes from
moving landwards. As soon as pioneer psammophilous vegetation develops,
accumulation and consolidation of windblown sand occurs on the spot, which
greatly affects the geomorphological evolution of the dune.
As vegetation develops permanently only at a certain distance from the coastline, the formation of shore dunes may only occur parallel to the coastline
itself, as they only partially depend on the direction of the main winds.
ORIENTATION OF WINDS
UPWIND FACE
LEE
15
■ Dynamics and formation of sand
shore dunes
16
Eroded sand which is carried and
deposited by wave motion and winds,
often accumulates inside small bays
(so-called crescentic dunes), or forms
lateral, leeward longshore bars which
close off small, shallow bays or join
islets near the shore with the coast,
producing peninsulas. When longshore bars are covered with dunes
Dune systems at Is Arenas (western Sardinia)
they are called beach rock.
are among the most extensive in Italy
Longshore bars, which are often
inappropriately called strands, may look like islets or elongated peninsulas, or
join the mainland at both ends.
They are outcropping underwater banks where large quantities of debris slowly
emerge as sand mounds. Instead, beach cusps have peculiar, cuspidate or
triangular shapes. They occur when debris is carried by two opposite waves
beach cusp
beach
lagoon
barrier islands
hollow beach
estuary
cliffs with beach
Geomorphology of a coast
the uprush of which concentrates towards protruding points (apexes)
separating two diverging coastlines.
Beach rock is composed of sand dunes shaped by wind and wave motion
which form on beach cusps. As their transversal length is very short, they are
extremely fragile and dynamic environments. The evolution of beach rock
sometimes leads to the complete erosion of longshore bars. The continual
drifting of the coastline seawards (which is associated with river supply of
incoherent material) may cement beach rock to sub-coastal fossil dunes (or
paleo-dunes).
These environments are very interesting from the naturalistic point of view,
and their evolutionary balance is very fragile, as it is linked with the continual
transformation of the substrate and surface sheets. The formation processes
of beach rock may lead islands to become part of the mainland, in the shape
of peninsulas. A typical example is the Argentario Promontory, where two
active beach rocks and a central longshore bar, with the town of Orbetello,
joined the mainland. These three longshore bars gave rise to two shore
marshes.
■ Substratum of beaches and dunes in Italy
The geomorphology of substrates is determined by the analysis of modelling
factors and particle size of elements which constitute them. When beaches and
dunes are considered habitats, the chemical mineralogy of substrates is highly
important i.e., the identification of mineral components which constitute grains
and, therefore, the chemistry of substrates themselves. Grains which make up
beaches and dunes are usually carried by rivers into the sea or directly to
beaches, and their mineral content depends on the type of rock outcropping in
the river basin itself. Furthermore, different rocks, and the different minerals
which compose them, have different resistance to erosion and transport and
therefore, if particle size is equal, more resistant grains may be carried farther.
For instance, among common minerals, quartz is the most resistant and is frequently found in beaches formed by rivers which cross long plain stretches.
Sand grains are carried by rivers, but their distribution is not symmetrical with
regard to watercourse outlets in seas. Sea currents scatter them unevenly. In
the upper Adriatic, for example, fluvial deposits sediment westwards with
regard to mouths; in the river Isonzo, deposits reach Lignano, and in the river
Tagliamento, they reach Jesolo and mix with those of the river Piave. The latter scatter as far as the lagoon of Chioggia.
Supply origin produces different particle sizes and mineral contents which are
17
18
linked to one another in some way. As regards the upper Adriatic, northern
beaches, the tributaries of which drain the Alps, have particle size classes of
95-99% between 2-0.03 mm; beaches near estuaries which flow on marlsandstone deposits of the Appennines have higher percentages of finer elements (between 10-20% of grains smaller than 0.03 mm). However, mineral
contents may have greater and more complex variations, and the following
values are only indicative.
In the stretch between Grado and Lido di Venezia, 80-90% of minerals are of
calcareous-dolomitic origin with 20% of quartz and flintstone, as the rivers
which supply these areas drain calcareous rocks.
Beaches supplied by the rivers Adige and Brenta are richer in quartz (about
40%) and other elements of acidic vulcanic origin (which decrease in the
Romagnese area) and fewer - 15-30% - carbonate elements (calcareous and
non-dolomitic). Southwards, in the Marches and Abruzzi, the carbonate content rises (30-60%) and quartz decreases (20-40%).
In the Campania and Latium regions, there are high quantities of feldspar
(20%), with quartz (25%) and calcium (40%). Tuscan shores have low quantities of calcium north and south (about 20%) and rise in central areas (50%).
The opposite happens with quartz, which peaks north and south (over 50%),
drops in the centre (20%) and peaks again near Follonica (60%).
Beaches in northern Sardinia are mainly composed of calcium (between 3080%) and quartz (10-30%). Towards Sassari, calcium drops to 10% and quartz
reaches 40%; the same occurs in the Gulf of Orosei. The area around the city of
Alghero has many variations, but quartz and calcium always prevail. All
Sardinian shores are characterized by iron (1-3%). In Sicily and shores around
Catania, there are large quantities of quartz (60%) and little calcium (20%).
Aerial view of Argentario area, with beach cusp surrounding Lagoon of Orbetello (Tuscany)
Aerial view of sandy Adriatic shore between Bibione and Bibione Pineta (Veneto)
Left: a natural beach; right: man’s intervention is clearly visible
19
Paleogeography and biogeography
PAOLO AUDISIO · GIUSEPPE MUSCIO · SANDRO PIGNATTI
The biogeographical structure of Italy is affected by the complex position of
the Italian peninsula, which is wedged into the Mediterranean basin. The present flora and fauna, likely the most numerous and dissimilar of all Europe, are
influenced by the geological evolution of this area which, in the last million
years, has been associated with different European and circum-Mediterranean
areas. The description of Italian beaches and dune systems must include the
whole Mediterranean and its recent history, at least until the most important
events which determined both the present shore morphology and its animal
and plant communities.
■ Paleogeopraphic, paleoclimatic and biogeographical outlines
About 65 million years ago, in the Paleocene, at the beginning of the Cenozoic
epoch, Europe and Asia were separated by a narrow, epicontinental sea
stretch (i.e., with shallow waters) which joined the present marine areas of the
Persian Gulf with the Artic Sea, passing eastwards of the present boundary of
the Ural Mountains (Turgai or Uralian Sea). Eastwards, the Mediterranean was
linked with the Indian Ocean, forming a partly epicontinental sea which was
narrow in width in some points, but incredibly long, known as Tethys. The
Italian and Balkan peninsulas had not yet formed, and there was a tropical or
sub-tropical climate along the margins of the Tethys.
Towards the end of the Eocene, about 40 million years ago, the Tethys could
still be found along the east-west line, but the Turgai Sea dried out, creating a
terrestrial passage between Asia and Europe.
In the Oligocene, about 36 million years ago, Eurasia was a vast area which
included most of today’s northern Asia and central-northern Europe, and
southwest, some areas started outcropping from the sea, which would later
become the present north Mediterranean lands. As the African and Eurasian
continental plates drifted towards each other, the Alpine orogenesis started,
and the Tethys began narrowing eastwards. Like a macroscopic puzzle, pieces
outcropped and organized into what became their present positions, such as
the Italian peninsula and its islands. In the west, Corsica, Sardinia and the
Sea bindweed (Calystegia soldanella)
21
22
Balearic Islands were still part of the Catalan-Provençal area but, in the early
Miocene (about 23 million years ago), they slowly drifted away and started a
migration which took them to their present position. Micro-plates sub-parallel
to the Sardinian-Corsican-Balearic Arch started moving and formed the
Calabrian-Peloritan Arc in the east and the coasts and sub-coastal mountains
of today’s northern Algeria in the west. In the south-east, the Apulian Peninsula
slowly outcropped, although still connected in the Oligocene to other areas of
the Balkans, the central-eastern Mediterranean, and western Anatolia.
In the same epoch, the African and European plates kept drifting towards each
other, giving rise to other important mountains in the east; at the same time,
sea levels lowered, due to the formation of the western Antarctic ice cap. The
Tethys progressively closed in the east and the African and Eurasian flora and
fauna, separated until then, could meet.
About 15 million years ago, the western part of the Tethys, which was about to
separate from the Indian Ocean, divided into two distinct stretches: southwest, in what became the Mediterranean Sea, and north-east, the so-called
Parathethys, which extended to south-eastern Germany and Pannonia, quickly changed from an epicontinental, shallow sea to a brackish “lake-sea” and
dried out. The remains of this epicontinental sea are the Caspian Sea and the
Black Sea, which only later was linked with the Mediterranean again.
Fewer than 6 million years ago, another devastating event affected the
Mediterranean area: the large sea stretch between today’s Iberian Peninsula
and the Baetic Rif chain of the African plate closed very quickly, separating the
Mediterranean Sea from the Atlantic Ocean. This phenomenon was due to the
combined actions of the Earth’s lowering sea levels and the outcropping of
areas along its coasts. This affected coast morphology only locally, but
influenced the net hydrological balance of the Mediterranean very negatively.
Today, of the annual 1400 km3 of freshwater supply (water from catchment
basins and rainfall), 4800 km3 evaporate in the atmosphere, with an annual net
loss of about 3400 km3. Considering that the total volume of water of the
Mediterranean is about 3.7 million km3, it is easy to calculate what could
happen today if the Strait of Gibraltar (and also the Suez Canal) were suddenly
closed. In a thousand years, the entire Mediterranean would dry out
(3.7million/3400 = 1088 years, but even fewer, because rainfall in the whole
dried area would reduce locally and move eastwards).
What happened in the Miocene is exactly the same as we have described in
Paleo-geography of Mediterranean in Paleocene. Brown: exposed areas; grey: platforms: pale blue: sea;
approximate position of Sardinian-Corsican plate also shown
Paleo-geography of Mediterranean in mid-Miocene. Brown: exposed areas; grey: platforms; pale
blue: sea
23
24
the science fiction hypothesis above: in the Messinian, 5.6-5.0 million years
ago, the Mediterranean partially dried out, coastlines drifted centripetally
towards and around the deepest areas, and essential terrestrial connections
were formed for hundreds of thousands of years between northern Africa, the
Iberian Peninsula, Sicily, Corsica-Sardinia and Italy. The Tyrrhenian and part of
the Sicilian Channel became large brackish seas, where rivers coming from
outcropping lands poured their waters hundreds of metres below ocean level,
creating deep gorges. This drying out had serious consequences on the biotic
communities, particularly sea organisms, which were confined in hyper-brackish lakes and largely died out due to this devastating “salinity load”. Among
terrestrial fauna and flora, the most xerophilous, thermophilous and
halophilous elements (among plants, e.g., Tamarix and many halophilous
chenopods) of northern African, middle-eastern and central-European origin
were distributed along the coasts and sub-coasts. Many mesophilous and
hygrophilous elements, which lived in rivers, lakes or mountain areas, also
used these new terrestrial connections to colonize western Mediterranean
areas, giving rise to endemic species. Other elements moved westwards and
reached the forming Italian peninsula. During the Messinian and the dry period
Paleo-geography of Mediterranean in upper Miocene (Messinian). Brown: exposed areas; pale blue: sea;
shaded: evaporating seas
Beachmarkers
Most handsome
fungus beetles of the
lycoperdine
(=eumorphine) subfamily
live in woodland
environments, particularly in
tropical or sub-tropical
countries where these
small insects feed on tree
fungi. Dapsa are a genus
of small lycoperdine
beetles, which have
adapted to life in piles of
stranded plant debris on
beaches and coastal salicornia
vegetation. In the late
Oligocene, probably starting from
north-eastern parts of the Tethys, the
most ancient members of this genus
began to spread westwards, rapidly
colonizing damp, sandy environments
near coasts throughout the Tethys,
from the north-eastern Atlantic to the
north-western Pacific. After several
phases of marine transgression and
regression, various populations and
species of Dapsa followed the
evolution of both Tethyan and paleo-
Paolo Audisio · Alessio De Biase
Mediterranean coasts,
which left them isolated
inland, in areas once
splashed by epicontinental
seas (such as the Paratethys).
Other Dapsa were affected by
the tectonic emergence (e.g.,
Canary Islands) or migration
(e.g., Kabylic microplates in
northern Algeria) of entire
circum-Mediterranean
islands. Lastly, about 40
species differentiated, most of
them on the coasts of what is
now the Mediterranean Sea, the
islands of the Canaries, Madeira,
and the Azores, but many of them
remained isolated in continental areas
where the sea had dried up millions of
years before, and thus adapted to
damp woodland or bank ecosystems.
If the present distribution of Dapsa
were to overlap that of marine areas of
the middle Miocene (about 12 million
years ago), we would see how these
rare and curious beetles may be
considered true “beachmarkers” of
coastal paleo-systems.
25
26
which followed the partial drying out of the Mediterranean, which had become
an almost brackish desert, many plants died out in terrestrial habitats.
In the late Miocene, about 5 million years ago, and early Pliocene, the Strait of
Gibraltar formed, creating a sea passage between the Mediterranean and the
Atlantic Ocean. The Mediterranean filled up and sea fauna of Atlantic origin
flowed in. The post-Messinian re-population of land habitats occurred both by
means of immigration from nearby areas and development of autochthonous
elements which had moved to the preserved mountains and river estuaries
during the dry period. Although the Messinian was rather short, the
development of today’s Mediterranean flora and fauna belongs to a later
period. The Italian peninsula and Sicily were forming, and coastlines adjusted
to present altitudes, not very different from what they are today. Northern Italy
was an exception - where a large gulf occupied the present Po Plain, which
outcropped only 2 million years ago, in the middle-upper Pleistocene. Marine
phases were more or less like those of today from the Pliocene until the
Holocene. However, the climate was sub-tropical and flora was quite different
from today and more similar to that of south-eastern Asia.
In the Pliocene, the climate, which had been dry in the Messinian, became
warm-humid and temperate again, and many plant and animal species came in
from the north and east. The situation worsened again with the formation of the
terrestrial Isthmus of Panama, which links southern and northern America,
because it modified the transport cycle of warm tropical currents to the
northern Atlantic, which became colder. This, and other complex astronomical
factors, gave rise to the formation of Arctic ice caps, the cooling of the northern
hemisphere, and the sudden adaptation of European and Mediterranean fauna
and flora to a temperate climate. Many xerophilous, thermo-hygrophilous or
sub-tropical marine and terrestrial species died out. Among terrestrial
elements, many found refuge along the sea shores and mouths of rivers, where
temperatures and waters were more suitable. A few million years ago, in the
early Pleistocene and Quaternary, climatic cooling became cyclic, and
glaciations started, with at least six main peaks along the length of ice caps in
the northern hemisphere and Euro-Mediterranean areas. During glaciations, the
climate cooled down and large ice masses of 1000-2000 m formed in Europe
near Alpine and Scandinavian areas. Ice and the higher mean density of cold
water deprived the sea of this liquid, and sea levels dropped more than 100 m.
The coastlines of low seas, like the Adriatic, outcropped for hundreds of
kilometres, followed by their coastal and sub-coastal fauna and flora. This also
created new pathways or brought small, sub-continental groups of islands
near, like the Italian Peninsula, the northern Balkans, Sicily, northern Africa,
Sardinia and Corsica. Large numbers of Siberian or central-Asian species
moved towards south-western Europe and reached the Mediterranean, where
they colonized sub-mountainous areas, cool and damp plains and coasts.
During temperate interglacial periods, some of these species moved to higher
altitudes, others died out, and some survived as relicts near mouths of perennial
rivers. At the same time, important steppe species of central and south-western
Asia moved to south and western Europe, as far as the Mediterranean coasts.
Many of these species died out in the following glaciations, some of them
moved to high altitude steppe-like habitats, but a few survived and adapted to
typical coastal habitats of both cliffs and dunes. In the Holocene, well after the
last glaciation (called Würm, dating back to 20,000 years ago), there still were,
although to a lesser extent, cold and hot peaks. An important hot maximum
occurred 8500 years ago, another between 5000 and 3000 years ago. During
the latter, many Mediterranean species, which still live on beaches and sand
shores today, were able to move to north-western Europe.
During the Roman Empire, the climate became warmer and temperatures
rose, particularly in central-northern Europe, until the 12th century, when they
cooled a little until the 18th century. Since then, temperatures have risen slowly, and continue to do so now. Further information regarding climate evolution
and its possible consequences on coastal environments is provided in the
chapter on preservation and management of sandy coastal ecosystems.
Paleo-geography of Mediterranean in Würmian. Brown: exposed areas; pale blue: sea; green: large ice covers
27
28
■ The present bioclimate
All Italian beaches and dunes lie on the Mediterranean (there are no significant
dunes inland) and the plant and animal communities of these environments
depend on the biogeography of the Mediterranean, although they have different
biogeographical problems.
The biogeographical Mediterranean area is defined according to its climatic
characteristics: mean annual temperature between 14° and 18°C, more or less
abundant rainfall (400-900 mm, locally exceeding 1500 mm) during the winter,
and 2-5 dry months in summer. Mean temperatures are never below 0°C, with
occasional snow or frost. These characteristics are suitable for evergreen
species, which can photosynthesize also in winter and reproduce in beach
environments. These are the prevailing conditions throughout the Mediterranean area, and may be found also in other areas of the world, such as California, central Chile, southern Africa, and western and southern Australia.
As regards coastal environments in Italy, not all of them are associated with
Dune systems consolidated by vegetation along south-western Sardinian coastline
Mediterranean characteristics. “Mediterranean” refers to the climate, not to
the geographical position. In Italy, the islands, the western coasts of Liguria
and Calabria, the Ionian coasts and Apulia have a Mediterranean climate.
Coasts of the Po Plain have a cooler climate (mean annual temperature of 12°13°C) with little, but regular rainfall in summer. The upper Adriatic has therefore
a temperate mid-European climate, and the Marches, Abruzzi and Molise have
a transitional climate which becomes Mediterranean only in Apulia. These climatic characteristics determine the type of flora, fauna and vegetation, but
there are also local features. As regards beaches, they are influenced by sea
thermoregulation, which becomes warmer in summer and releases heat in
autumn and winter. Waters which had cooled in winter, absorb heat in spring
and summer, giving rise to a temperate coastal climate. This effect is clearly
perceived along the Adriatic coast, which is not very deep, closed on three
sides, and tends to overheat during the summer.
■ Phytogeography
The floristic elements of the Mediterranean are similar to those of nearby continents (Africa and Eurasia) and associated with western or eastern migrations
and intense, local speciation (autochthonous element). There are many
endemic species, according to Quèzel and others, about 25% of the flora.
The situation on beaches and dunes is different, as there are few continental
and endemic groups. Most species are associated with past floristic connections with the east and west.
The western element is constituted by widely distributed species of the
Atlantic coasts or associated with ocean flora. These species moved to the
Mediterranean during the late Messinian, when the Strait of Gibraltar opened.
Although there is no proof of this, Ammophila arenaria, Elymus farctus,
Euphorbia paralias and Calystegia soldanella seem to belong to this group. But
biologically, every species is different. Euphorbia paralias and Calystegia soldanella are found also on the Atlantic coasts, their seeds or rhizomes are easily carried by the current, and their direct migration is possible. Ammophila is
clearly associated with the west, as this species is found both on the Mediterranean and Atlantic shores, but not on those of the Red Sea or Indian Ocean.
This species is not associated with other groups of shore grasses, but with
large, desert grasses. Instead, Elymus belongs to a group usually found in
Asian deserts, which spread towards the Atlantic coasts and then returned to
the Mediterranean, as the gradual increase in its chromosome numbers
shows. It may be a good example of post-Messinian immigration.
29
30
Saltwort (Salsola kali)
As regards the eastern element, it is associated with the Thethys, and therefore
it is older than the Atlantic group. The most important elements are species
typically found in brackish deserts of central Asia and the Near East, such as
chenopods, members of the plumbago familiy, bean-capers and a few groups
of composites, jonquils and grasses. Their typical morphological adaptation is
succulence and they are highly resistant to salinity. However, these adaptations
are not relevant with regard to beaches and dunes, as the sand of these
environments have low sea salt contents. This flora is typical of brackish
environments, lagoon shores, and sometimes marginal beaches. Among these
are the chenopod Salsola kali and perhaps the crucifer Cakile maritima, which is
also found on Atlantic coasts.
The flora of the Mediterranean is clearly different from that of temperate, brackish European lagoons, as Atlantic coasts are subject to intense tidal variations
of several metres. Instead, in the Mediterranean, tides undergo slight variations
(2-3 decimetres). In Italy, the only exception is the high Adriatic, where there are
remarkable differences between low and high tides (70-90 cm or more, during
syzygial tides), which constitute a serious problem to Venice, although they
cannot be compared with those of the Atlantic. These conditions affect the evolution of flora: in the Lagoon of Venice, there are large populations of the grass
Spartina stricta (= S. maritima), an Atlantic species which is exclusive to this
area of the Mediterranean, and among algae, Fucus virsoides, the only Mediter-
ranean representative of Fucaceae
(brown algae, widely distributed along
Atlantic coasts). Both species are
closely associated with life in tidal environments. However, these ecological
conditions have not caused speciation
in the beach flora. Actually, beach
plants are always located above high
tide level and avoid the consequences
of this phenomenon, otherwise remarkable in some animal groups.
There are a few autochthonous elements of beach and dune flora, and
although many psammophilous species
live in the Mediterranean, none of them
seem autochthonous to Italian beach
environments. This contrasts with rupeBack-dune vegetation with Limonium
stral flora, the many endemic species of
which live in restricted coastal areas, particularly the genus Limonium (plumbago family), but there are also representatives of completely different groups
(such as Anthyllis, Antirrhinum, Centaurea, Dianthus, Erodium, Helichrysum,
Primula, etc.). Instead, the few species endemic to beaches and sand dunes in
Italy are the result of differentiations of continental elements, e.g., Centaurea
tommasinii and Silene colorata. Despite these limitations, sandy shore flora is
peculiar, in that no marine sand species may be found in continental environments, and very few continental species survive on beaches. Flora of sandy
beaches is therefore unique. This is particularly evident along the coastline,
where marine environments are particularly selective. Proceeding landwards,
continental elements often found on sand dunes prevail where the sea influence
is hardly felt. Therefore, beach flora and vegetation are not, as is often thought,
differentiations of continental flora caused by the sea influence, but are usually
composed by completely different species. They originated in areas far from the
sea (often far from the Mediterranean), and colonized areas between continental
environments and the sea. Beach vegetation is therefore a kind of diaphragm, an
interface linking marine and continental environments.
In conclusion, highly specialized flora of beaches, which differs completely
from continental flora, may be considered a mark of biodiversity. This type of
flora is the result of more or less uniform processes in the Mediterranean,
which did not give rise to large micro-evolutions of single groups or areas.
31
32
■ Zoogeography
The historical, biogeographical events and the dynamic processes which produced the present beach fauna in Italy are obviously very similar to those which
originated plant communities, although with very different endemic species,
numbers and relict populations. Faunal and floral differences may be very small
or great, according to different environments (intertidal, damp sand beach, of
dune or psammo-halophilous or psammo-hygrophilous fauna of interdunes
and salicornia, etc.) and taxonomical groups, their trophic roles and speciation
degrees. Undoubtedly, most fauna living near sea-land (intertidal and damp,
sandy beach fauna), despite its active dispersion, is widely distributed in both
the Mediterranean and Atlantic areas; some may even be cosmopolitan or subcosmopolitan. This is not surprising, because many of these organisms can
withstand large temperature variations, long exposure to sea water, and physiological stress. In coastal environments, they are therefore suited to move or be
carried by sea currents, wind, birds or man’s activities. These are mostly ecologically and trophically specialized elements which are exclusive to these environments, but may actively or passively disperse, or undergo metapopulational
dynamics (groups of small, local populations which are closely connected to
one another and change continually: they die out locally and recolonize the
same area). In the last million years, these elements have easily adapted to
shore variations in both the Mediterranean and Italy, showing their poor skills at
specific differentiation.
The fauna of arid, damp or brackish dunes and dune heathland is very
different, i.e., specialized invertebrates, such as detrivores, saprophagous,
psammophilous and psammo-halophilous, or phytophagous organisms
associated with psammophilous plants. In these areas, characteristics such
as “rarity”, “small local populations”, “high trophic specialization”, “little
dispersion” and “habitat fragmentation” have efficiently interacted to produce
endemic organisms of restricted, fragmented or relict areas. As described in
the long chapter devoted to invertebrates, both types are interesting from the
point of view of conservation and biogeography alike, especially those
species colonizing southern coasts of Sicily and Sardinia or western Italy.
It is extremely difficult to determine periods of penetration and isolation of
coastal fauna in Italy. As regards beaches, zoographical historians are often surprised by unexpected active and passive dynamics of many species or genera,
the presence of which in Italy is certainly due to specific paleogeographical or
paleoclimatic events. It is therefore worth indicating only significant fauna, which
was certainly affected by these specific phenomena. Obviously, a few exceptions may become the rule when dealing with large numbers. In Italy, most
coastal fauna is recent, influenced by the Quaternary paleoclimatic events.
Shore environments (sandy ones in particular) were literally “last resorts” for
Pimelia grossa (darkling beetle), a typical Sicilian-Maghrebian species
Sepidium siculum (darkling beetle), endemic to Sicily
33
34
Distribution of beach-dune systems in Italy
Descriptions of sandy beach systems
seldom include the dunes and
heathland which compose them, as
man’s harsh intervention in the past
century has destroyed many of them.
More than 3000 of the 7500 km of the
Italian coastline are composed of
beaches used by man. In spite of this,
Italian coasts do have beaches made up
of beach cusps, small, almost hidden
bays, sometimes beneath rocky cliffs,
near ports, or accessible only from the
sea. The sandy coastline of the Adriatic
stretches more or less uninterruptedly
from Monfalcone to the Gargano, with
the sole exception of the Conero
Promontory (Ancona) and a few areas
between Ortona and Vasto. The
northern portion of this beach,
interrupted by the lagoons of GradoMarano and Venice-Chioggia,
constitutes the largest Italian dune
system, and is made up of a series of
continual sandy beaches from Grado to
Rimini. The high Adriatic beaches have
low gradients, between 0.3 and 0.7%
from the coastline to the 5-m contour
line, rising to 1% near the city of Pesaro
and between 3 and 8% in the Monte
Conero area.
The entire dune system is the product of
a long period of coastal stability, which
occurred at the end of a warm climatic
phase after the last glaciation. The
system is thought to date back to 5000
years ago, when the natural subsidence
of the coast, which had started a very
long time before, was balanced by the
rise in sea level after the Alpine ice cap
melted. In those times, the climate was
warmer than it is today, and this enabled
holm oak to spread along the coasts,
where it is still found today in isolated
groups on the dunes of Mesola,
Paolo Audisio · Giuseppe Muscio · Sandro Pignatti
environmental quality may still be found
between Bibione and Caorle, and from
Chioggia to Ravenna.
Beaches extend along the Adriatic coast
south of Rimini, to the Marches and
Abruzzi, as far as the city of Pescara,
but here they are narrower, restricted
inland by the railway, roads, towns and
land used for growing vegetables. The
Adriatic coast also contains a wide,
sandy area between Termoli and the
Rosolina and Bosco Nordio near S.
Anna, just south of Chioggia. Later, the
river Po flooded this dune system,
which today is separated from the sea
by a few kilometres of land. On the
delta, the mouth of the river Po moved
inland, to an area once occupied by the
sea. At the same time, the sea flooded
the dunes in many areas, giving rise to
lagoons.
The formation of deltas and lagoons are
historical events which are chronicled in
documents of the period. For centuries,
starting from the Middle Ages, the Most
Serene Republic of Venice carried out
extensive hydraulic works to maintain
the Lagoon, even undertaking such
gigantic tasks as the diversion of rivers
which flowed into it and building murazzi
(long seawalls) on the seaward side.
These works contributed to the
modelling of the shoreline, and
continued until the 20th century. In spite
of massive human interventions, the
high Adriatic dune system still has the
most extensive beaches in Italy; in
recent years, they have been used for
tourist purposes, thus bringing
prosperity to an area which had
previously been malarial and almost
deserted, the environmental importance
of which is evident. Areas of good
TN
AO
VE
MI
TO
TS
BO
GE
FI
AN
PG
AQ
ROMA
NA
CA
PA
ROCKY COASTS
SANDY COASTS
northern part of the Gargano
promontory, the “spur” on Italy’s boot.
The southern Adriatic and the Ionian
have alternating high, rocky coasts and
sandy beaches. Beaches extend only
south of Manfredonia; then, in the
remaining Apulian area, there are mainly
rocky coasts, which sometimes contain
narrow dune systems, especially in
Salento (see photo). Extensive dune
systems may be found between Taranto,
Metaponto and Policoro (gradients
between 1 and 1.5%), and broad
beaches are preserved at the mouths of
the largest rivers (Piana di Sibari, Lidi di
Catanzaro). The lower Tyrrhenian in
Campania, Basilicata and Calabria has
similar characteristics, with alternating
high, rocky coasts and small sandy
beaches (Piana di Gioia Tauro, Piana di
Sant’Eufemia, Golfo di Policastro) some of these beautiful beaches are
known only locally. Moving northwards,
there is the large Piana del Sele, which
stretches from Paestum to Salerno:
Beaches are again found in the
Sorrento peninsula, but only in a
few stretches along the
CB
volcanic portions near
Naples. Sandy
BA
beaches dominate
from Terracina
PZ
northwards,
interrupted
by a few
rocky
promontories
(Circeo, Civitavecchia,
Argentario, Uccellina,
Livorno, Punta Ala,
RC
Piombino). The mean
gradient tends to decrease
northwards (1% near Viareggio).
Liguria mainly has a high rocky
35
36
37
Distribution of beach-dune systems in Italy
coastline with a few small sloping
sandy beaches (gradient 3-6%) near
river mouths.
There is then a second long stretch of
beach along the high and middle
Tyrrhenian between Viareggio and
Piana del Sele. Here, the coastline is
different from that of the Adriatic, not
only in morphology, but particularly in
plant communities, which have more
Mediterranean characteristics on the
Tyrrhenian. Among the species which
cannot be found on the Adriatic are
large numbers of agamospecies of
Limonium (the groups L. multiforme, L.
pontium, L. remotispiculum, and
others), dwarf fan palm (Chamaerops
humilis) and Anthyllis barba-jovis
(Jupiter’s beard) usually found on
rocky coasts. Beaches and coastal
maquis also contain species which do
not colonize the eastern shores.
The largest Italian islands also feature
wide beaches, sometimes wellpreserved but usually densely
populated by tourists in summer. In
Sicily (especially in the north), coasts
are high and alternate with short sandy
beaches near bays and river mouths.
The mean gradient of these beaches is
between 1 and 2%. The once beautiful
and natural beaches near Palermo,
Mondello and Sferracavallo are now
largely populated, with the exception
of the Golfo di Castellamare. The only
long, extensive sandy beaches which
are still of environmental importance
are those on the south-western part of
the island, on the Canale di Sicilia
(particularly those around Gela), near
Siracusa and Ragusa, and the Piana di
Catania.
In Sardinia, the most important
beaches are in the west and south, on
the Golfo dell’Asinara, Golfo
d’Oristano and Sulcis, Poetto and
Quartu, near Cagliari. Of particular
beauty are the dunes at Is Arenas (see
photo), south of Oristano, some of
which are higher than 10 m, and those
between Marina di Arbus and Capo
Pecora, again near Oristano.
This list contains only the most
important sandy beaches in Italy from
the naturalistic viewpoint, and omits
many extensive ones used for tourist
purposes, which have therefore lost
their environmental value.
Calicnemis latreillei (dynastines), a psammo-halophilous specialized species living in scattered coastal areas
many floristic and faunal elements which migrated during the severe climatic
changes of the Plio-Pleistocene epochs. These recurrent phenomena largely
affected the European and Mediterranean areas, where dunes characterize
long peninsulas (like Italy) or large islands, which offered shelter during cold
periods. The combined effects of the “last resort syndrome”, falling sea levels
during glacial periods, and wide eastward and south-westward land bridges,
often caused multiple overlap of mostly xero-thermophilous fauna and flora,
not only in coastal or pericoastal environments (Mediterranean or subMediterranean maquis and garrigue), but also in steppe-like meadows, moorland and brackish, sandy environments near rivers and lakes. Dune and dune
heathland ecosystems as narrow “thermophilous ecological isthmuses”
played an essential role during glaciations. Many halophilous, hygrophilous
and moderately thermophilous organisms from northern areas, but also from
the south-east (Balkans), and south-west (Sardinia, Corsica, Sicily, North
Africa) may have reached the shores by exploiting the emerging land bridges.
During the Messinian and Oligocene, southern areas in Italy, such as Sicily and
Sardinia, were colonized by many xerophilous, psammo-hygrophilous or
psammo-halophilous elements of North African, Saharan or South-West Asian
origin, which survived and differentiated locally. These phenomena have given
rise to large numbers of specialized animals (primary and secondary psammophilous or psammo-halophilous organisms) in dune environments with
regard to the total number of species which constitute biotic communities.
Beach vegetation
SANDRO PIGNATTI
■ Plants colonize beaches and dunes
It might be surprising to realize that, although beaches usually attract those
who want to enjoy themselves, they are also extremely important from the
naturalistic point of view and constitute a small but essential feature of the
Italian cultural identity. For centuries, beach flora has been studied for its
peculiar biological and ecological characteristics. In 1787, J.W. Goethe, just
arrived in Venice, went to the Lido, which at the time was almost deserted, and
made his first contact with the Mediterranean beaches.
On that occasion, the sight of a stranded bovine skull helped him conceive the
theory of vertebral skulls.
Beaches or waterlines, in their seaward stretch, never contain vegetation.
Here, sudden variations in environmental conditions make life impossible: the
beach is impregnated with salt during high tide and storms and, when the sea
recedes, superficial sand dries up almost completely, so that even a small
shower may wash all the salt away. Here is where debris carried by waves
accumulates.
According to the type of bottom, debris may be composed of mollusc shells,
algae or seaweed such as Zostera and Posidonia. These organic remains are
then colonized by many animals which leave their “homes” quickly when
conditions change suddenly, such as marine species which climb pools and
humid sand, birds or flying insects.
As regards plants, which cannot move, this environment is absolutely
inhospitable: their seeds are scattered everywhere by continual sand stir. If
embryo plants were able to germinate, they would undergo an alternating
stress of salinity with high-tide and hot and dry conditions, with intense
exposure to the heat of the sun. These conditions are so extreme that no
vegetation can withstand them.
This is why only fauna lives on the waterline. Landward areas above the
maximum high-water line, reached only by exceptional storming waves, are
colonized by the first plant communities.
Crucianella vegetation in Argentario (Tuscany)
39
40
Pioneer plants. In the first strip of
beach, usually more than 50 m from
the coastline, vegetation is composed
of ephemeral species, plants which
germinate in autumn or late winter and
live for 1-2 months. In this period, they
flower, fructify and then dry up. In early
June, fruits germinate and release
seeds, which are covered by sand and
lie quiescent until autumn. The most
common species is the succulent
Cakile maritima (sea-rocket). Further
Elytrigia juncea
landwards, there are perennial grasses
such as Elytrigia (beach grass) and
Ammophila (sand reed), the dispersion of which gives rise to sand dunes.
Cakile colonizes this area only occasionally, and is associated with other
short-living species like Salsola kali and beach spurges (Euphorbia peplis),
which cover only 5% of the sand. At the end of their lives, only a few dry twigs
remain, which are then carried away by the wind. Their seeds germinate the
following year, in other areas. This pioneer, totally unstable phase is enough to
hinder windblown sand, which starts accumulating in certain points.
The dynamic trinomial
Inland beach stretches tend to shape
themselves into mounds about 4-6
metres high: dunes. Narrow beaches
may only contain piles of sand
accumulating on the banks or slopes
of coastal roads, but extensive sandy
stretches contain dune belts which are
hundreds of metres long.
Visitors are immediately attracted by
them and stop to camp, but dunes are
also typical subject matter for
naturalists.
The first scientific interpretation of this
environment came from the French
scientist, Kuhnholz-Lordat, who
considered dunes to be produced by
the interaction between wind and
vegetation, constituting the so-called
“dynamic binomial”. However, a third
element was needed - i.e., sand because otherwise, on rocky
substrates, dunes cannot form. We
may therefore call this the “dynamic
trinomial”:
WIND
SAND
DUNE
Sea-rocket (Cakile maritima)
Sand reed (Ammophila littoralis)
VEGETATITION
Sandro Pignatti
Sea breezes, which blow almost every
day, carry sand inland, and the
vegetation which then colonizes it is
an obstacle where sand accumulates
further, forming dunes. When strong
gales blow, the highest and most
exposed areas of dunes are eroded
and their sand is carried even further
inland - in other words, the higher the
dune, the more intense the process
has been. As a sort of compensation,
accumulation and erosion balance
themselves to regulate dune height.
Ocean shores may have very high
dunes, up to about 20-30 metres.
Dunes are special environments. Sand
grains do not absorb water and
therefore plants must adapt
themselves both to little or no water
and to substrates the temperature of
which may be extremely high on sunny
summer days. Unlike what might be
expected, and in spite of the sea
nearby, the actual salt content of
dunes is very low, because the salt
carried by marine aerosol is easily
washed away by rain. Plant and animal
species must therefore contrive
adaptations if they are to survive in
these conditions.
41
42
Embryo dunes. These dunes are
characterized by Elytrigia juncea (better known as Agropyrum junceum), a
psammophilous (sand-loving) perennial grass. Their roots cannot reach
brackish water deep in the sand, and
only the seeds which fall on dunes
germinate. Unlike Cakile and Salsola,
Elytrigia produces horizontal rhizomes
which crawl along the sand or penetrate it. Their floral culms are 3-4 dm
high. The pioneer phase is followed by
real colonization: this is an essential
difference, because Elytrigia juncea is
long-living and permanently occupies
the land. Its stalks constitute obstacles where sand accumulates to a few
Sea holly (Eryngium maritimum)
decimetres, forming embryo dunes.
Other seeds may germinate far from
brackish water, and vegetation spreads out. Also in this case, surface cover is
limited to 20-30% of the total. A process of self-organization begins: vegetation creates its own environment.
gales usually bare the roots of Ammophila plants, which survive until new
sand is accumulated and roots may start their vegetative functions again.
Psammophilous vegetation develops with the creation of sand dunes. Among
beach herbaceous plants are Medicago marina (sea Spanish clover), Calystegia soldanella (sea bindweed), Cyperus capitatus (beach bean-caper),
Euphorbia paralias (sea spurge), Eryngium maritimum (sea holly), Echinophora spinosa (Thorny sea fennel), Pancratium maritimum (sea pancratium lily),
Lotus commutatus, Matthiola spp. (gillyflower), and others, which cover 5070% of the surface.
There is also a rich animal life, due to the large numbers of molluscs (especially Theba pisana). Their windblown shells, together with other stranded shells,
accumulate on the sides of dunes. Shells are fragmented, and the calcium carbonate of which they are composed is eroded, enriching soils with cations.
Ammophila are long-lasting, despite the continual wind variations. Seaward
dunes (white dunes) are exposed to marine wind and landward ones (grey
dunes) are more sheltered.
In the former, plants can survive only with special contrivances: Ammophila is
never completely covered by sand, because its leaves emerge from small
sand deposits; other species are annual, and depend on seed survival. In
sheltered environments, even plants which germinate near the soil (chamaephytes) may survive, although they may be damaged by sand stir. This gives
rise to further vegetation variations.
Dune formation. A further step in the formation of dunes is determined by
another psammophilous, perennial grass, sand reed - Ammophila littoralis (=
A. arenaria).
Ammophila and Elytrigia differ, although they belong to the same family.
Elytrigia has isolated culms and its flabby leaves are far apart, attached to the
sand surface. Instead, Ammophila has strong, erect culms, up to 1.5 m high.
Its leaves are also straight, and form thick shrubs over 1 m high. This plant
totally covers many square metres of surface, making it impossible to
determine if there is only one individual or many tangled up. This constitutes a
barrier for windblown sand, which accumulates among the stalks of
Ammophila, increasing dune height. As stalks and leaves grow, dunes rise.
The self-organizing process continues.
Dunes are very unstable environments. Sand accumulates at the bottom of
Ammophila, but the steep gradients of dune sides are intensely eroded. On
Tyrrhenian shores, a single, short south-westerly gale is sufficient to blow
away many decimetres of sand, which is carried to nearby dunes. These
Sea camomile (Anthemis maritima)
43
44
Sea lavender (Otanthus maritimus)
Variegated restharrow (Ononis variegata)
Ephedra (Ephedra sp.)
Consolidated dunes. Landward and
Ammophila dunes are the same height,
but the former are characterized by
gentle slopes, with low-gradient sides.
Ammophila is also present here, but its
individuals are smaller and less thick.
There are always sandy substrates,
with fine soil, which compact it further.
Surface cover is wider, owing to small
species. Windblown sand is almost
absent and erosive processes are highly reduced, due to the plant cover.
These dunes are quite stable.
On the Mediterranean coasts, these
environments are characterized by
crucianelletum, i.e., lignified psammophilous species, such as sea
chamomile (Anthemis maritima), Crucianella maritima, which gives the
name to this association, and sea
lavender, Otanthus maritimus (= Diotis
maritima). In Sardinia, there is also cliff
rose (Armeria pungens). The shores of
the high Adriatic, from Grado to Rimini,
are populated by scabious, Scabiosa
argentea var. alba and dogbane (Trachomitum venetum). Dune surfaces
are often carpeted with the moss Tortula ruraliformis and some lichens: this
cryptogamic vegetation grows during
the winter, when sand is more humid,
and may cover the surface completely.
Also annual species are widespread
and flower beautifully in spring, e.g.,
Ononis variegata (variegated restharrow) and Silene colorata.
It is worth noting that consolidated
dunes may occasionally contain lignified plants, usually shrubs or trees, but
here they are small, such as juniper, holm oak or lentisk on the southern
coasts, or Spanish broom (Spartium junceum) on the coasts of the Veneto
region. At present, these species are only occasionally found on coasts, but in
the future they may give rise to the coastal maquis or forest. Consolidated
dunes of southern Italian regions also feature other leguminous shrubs, such
as the rare Retama raetam subsp. gussonei (white broom) in Sicily, or the
unusual ephedra (Ephedra fragilis and E. distachya). Dunes along river mouths
throughout Italy and its islands or near dry rivers in the south often host
tamarisk (Tamarix spp.).
Interdunal hollows. The environment of consolidated dunes is influenced by
the flow of meteoric waters towards interdunal hollows. Material moves from
the dune top to its base: it is usually made up of fine grains and organic matter
produced by decomposed vegetal material. Water enriched with carbon
dioxide is slightly acid and dissolves the calcium content of sand and mollusc
shells which accumulate on the dunes. This is a run-off process, whereby
interdunal hollows slowly lower and compact. Fine material (silt and clay)
accumulates on the soil, and watertable waters tend to emerge by means of
capillarity. After long periods (decades or centuries), hollows between
consolidated dunes become humid environments or marshes in winter.
Dune and interdunal flora and fauna are completely different. Mechanical
problems associated with sand and wind motions are absent, and the main
selective factor is the ability of roots to reach the watertable. This is why
geophytes prevail here, i.e., plants with underground rhizomes like Schoenus
nigricans (bog rush), Juncus maritimus (sea rush), Juncus acutus (pungent rush)
and others. Salinity, which so far had been insignificant, here constitutes a
problem. Dune plants live on rain water and therefore do not need to be salinityresistant. Instead, interdunal plants draw water from the watertable which,
being close to the sea, contains marine water. Usually it is brackish, i.e., with
low salinity, but it undergoes seasonal variations: in winter, when rain is
frequent, it is almost freshwater, but in summer, little rain and high evaporation
make brackish water emerge and salinity concentrates on the surface. Plants
contrive various defence systems against this ecological factor:
- obligate halophytes (species which are exclusive to constantly low-salinity
environments), such as Erianthus ravennae (Po cane), Holoschoenus romanus
(minor rushe), Juncus maritimus, Juncus acutus, Limonium caspium, Plantago
crassifolia (succulent-leaved plantain);
- halo-tolerant species (which normally live in continental environments, but are
moderately salinity-resistant), like Blackstonia serotina, Centaurium spp.,
45
46
The importance of salinity
100
90
80
83 %
82 %
74%
70
65 %
60
59 %
50
40
37 %
30
26 %
24 %
20
18 %
14 %
10
0
BEACH
AGROPYRUM
AMMOPHILA
SCABIOUS
INTERDUNAL HOLLOWS
Particle size of sand on dune of Punta Sabbioni, Venice. Red: fine sand (200-50µ); blue: coarse sand
(1000-200µ)
Epipactis palustris (helleborine), Gentiana pneumonanthe (gentian), Molinia
altissima (grass), Phragmites australis (ditch reed), Plantago cornuti (Cornut
plantain) and Schoenus nigricans. In this environment there are also many birds,
which contribute to the balance of plant species.
It is worth recalling here a significant event. During World War II, at San Nicolò di
Lido, on the Venetian coast, concrete bunkers were built and disguised under
the ammophila dunes. At the end of the war (April 1945), they were blown up,
producing craters a few metres deep, at the bottom of which small brackish
pools formed. In the summer of 1950, these pools had been colonized by shore
sedges (Schoenoplectus littoralis), the twigs of which were higher than 1 m. This
species is not restricted to coastal life and has never been found on the island of
the Lido di Venezia, although it occasionally lives at the river mouths between
the Piave and the Isonzo. The nearest populations were therefore about 20 km
away. The fruit of sedges are small, round and smooth, and thus they cannot be
windblown. They could not have been carried by the current either, because the
San Nicolò pools were far from sea or freshwater. The only possible explanation
for their presence was that they had been carried by birds, because fruits can
attach themselves to feathers, or even more likely, they had been digested by
birds (endozoic distribution). It was really amazing to see how this species was
able to colonize these empty niches in such a short time.
Interdunal damp areas host flora of considerable ecological value, and interactions between species are extremely peculiar. However, these ecosystems are
disappearing quickly, as are all European humid areas.
As already mentioned, the ecological
factors hindering the establishment of
beach plants are sand mobility
caused by winds and difficulty in
finding water, not salt.
In order to understand the importance
of salt in beach environments, we
must bear in mind that sand is
composed of much larger grains than
those which normally make up
agricultural or woodland soils.
Soil has three components of
gradually smaller diameter: sand, silt
and clay. Inland soils are mainly
composed of silt and clay; those of
beaches contain almost 100% of
sand. Although sand grains are small,
they cannot form a compact mass
like those of clay and silt: the most
important characteristic of sand is
that it remains incoherent. This is why
it is so permeable.
Large quantities of salt are dissolved
in seawater (34-37%) - not only
sodium chloride, but also other
chlorides, bromides, sulphates, etc.
Seawater is taken up by sand and
constitutes a salty watertable: roots
reaching it would not be able to
absorb its water because of the high
osmotic pressure due to dissolved
salt. Dune plants therefore avoid the
salty watertable and stretch their
roots horizontally along the surface,
forming a thick network. Rainwater
Sandro Pignatti
moistens the sand and roots of
Ammophila (see photo), and other
psammophilous species capture it
before it can penetrate through the
sand and mix with the salty
watertable.
Dune species therefore live on
rainwater, like all other plants inland,
and cannot exploit the enormous
quantity of seawater nearby.
Salt in dune environments is only
carried by wave aerosol: near the
shoreline, the air carries large
quantities of water, the salt content of
which is very similar to that of
seawater.
In Italy, swash on the waterline in
breeze conditions is restricted
(although the situation may change
on ocean shores) and salt
accumulation is limited to a few
dozen metres, sometimes only a few
metres near the waterline.
This phenomenon may be enhanced
by winter storms along rocky coasts,
where salt may be carried 100 and
more metres above sea level.
Salty water borne by aerosol
accumulates on sandy surfaces and
on the plants which colonize them:
the water evaporates and the salt
remains in crystallized form, which is
usually harmless to plants.
When rain falls, salt, which is highly
soluble in water, dissolves, penetrates
the sand in a highly diluted form, and
does not disturb the plant further.
This is why dune plants are seldom
damaged by salt.
And this is also why plants in
interdunal hollows, which draw water
directly from the brackish watertable,
are suited to a completely different
environment to that of dune plants.
47
■ Shore maquis and forests
48
49
Sandy beach vegetation becomes very complex in the transition area to continental environments, where the surface contains lignified species. Maquis of
shrubs usually constitutes the pioneer phase, and when conditions are
favourable, it is replaced by high forest.
Shrub vegetation of dunes, usually large junipers, is only found where the
climate is Mediterranean. Cortège species are also shrub-like, such as lentisk,
wild olive, dwarf fan palm (Chamaerops humilis), myrtle (Myrtus communis),
angustifoliate phillyrea (Phillyrea angustifolia), pungent asparagus (Asparagus
acutifolius) and catbrier (Smilax aspera). Mediterranean maquis is exhaustively
treated in another volume of this same series.
Shore forests are chiefly constituted by pines, although this does not imply
that beach vegetation naturally hosts pine forests. Most pines have been
planted or kept by man. This is made evident by the type of trees: Pinus pinea,
P. pinaster and P. halepensis.
The first is spontaneous only in the southern Iberian Peninsula. In Italy, it is
always grown except, perhpas, in the Peloritan pine forest in Sicily. Cluster
pine (Pinus pinaster) is a continental species, typical of Liguria and northern
Tuscany. On the dunes of the Tyrrhenian coast it is cultivated. Aleppo pine is
Stone pine (Pinus pinea)
Cluster pine (Pinus pinaster)
Aleppo pine (Pinus halepensis)
50
spontaneous in warm Italian regions and islands, but is usually found in rocky
environments. Coastal pine forests, e.g., at Palinuro and Porto Pino in Sardinia, are probably cultivated.
Coastal pine forests are a beautiful sight but, environmentally speaking, they
are of little value if they are not spontaneous. Reafforested pine forests are
characterized by large deposits of pine-needles which suffocate or
impoverish the undergrowth. Eventually, pines are the only species left, as a
sort of mono-culture. Gradual deforestation is the only means by which
maquis species may be re-introduced in the Mediterranean area, normally
composed of holm oak groves.
On the high Adriatic coast from Ravenna to Grado, where the climate is temperate, broad-leaved shrubs (phillyrea, cornelian cherry, privet) gradually
replace pines and mark the beginning of oak forests. The most complex vegetation of landward dunes is dominated by oak: in the Mediterranean area it is
holm oak (Quercus ilex) and on the Tyrrhenian and high Adriatic coasts holm
oak forests mingle with common, Italian, Adriatic oaks (Quercus robur, Q.
frainetto, Q. cerris).
Mixed-oak forests are very beautiful environments (see the volume Woodlands of Po Plain in this series): the most imposing individuals may be 4-5
centuries old and 18-25 m high. Undergrowth flora is characterized by
shrubs, but there are also many types of herbs and grasses.
Holm oak forests have fewer floral species, because trees are densely
packed and their lush leaves shade the undergrowth. The chief species is the
evergreen holm oak, which is usually smaller than broad-leaved species (1220 m), but very lush in this environment. (see The Mediterranean Maquis in
this series).
■ Contrivances
In order to understand the way in which plant contrive to adapt to beach life,
it is worth studying a few, very peculiar ecological aspects of this environment. Its conditions may be considered extreme for plant survival, and thus,
psammophytes (sand plants) must overcome stress rates which would be
lethal to other plants. As we have already seen, stress is not due to salinity, in
spite of their closeness to the sea, but to environmental dryness and heat.
Dryness is caused by the physical characteristics of sand granules which
absorb only small quantities of rain, and only for short periods. Heat is due to
the sun, the rays of which stike the sand surface directly.
These two effects are partially linked to one another: heat makes humidity in
sand granules evaporate, contributing
to its dryness, and sand heats up
because it is so arid. Here, beaches
are covered with dunes and colonized
by woody species (maquis and forest).
This is due to the gradual accumulation of fine soil (silt and clay), which
retains more water, although quantities are always very small. As is wellknown, sand is completely dry during
the day, especially in summer. Roots
grow in depth, where humidity is
always very low, but they cannot draw
from the brackish watertable, which
would poison them.
There are varying temperatures on
beaches, as we may note in summer.
Euphorbia peplis, a creeping spurge on a
Sicilian dune
Sea water near the shore may reach
22°-25°C, and above the sea,
temperatures are slightly higher, usually 25°-30°C. Along the waterline, the
continual evaporation of water has a cooling effect and temperatures may be
lower. Proceeding landward, temperatures increase quickly, and at midday,
few people can walk barefoot on the sand: soles start hurting when sand
temperature exceeds 48°-50°C. On dunes, temperatures are even higher and
around 60°C or more.
The first consequence for plants lies in their difficulty in finding indispensable
water to keep their cellular metabolism active. Halophytes living on brackish
lagoon mud have a similar problem, which they have solved by raising the
osmotic pressure of their cellular liquids: they can absorb water from the
watertable filtering its saline content, which remains in the substrate. But this
is of no use to sand plants: if there is no water in the soil, it is impossible to
absorb it, and raising the osmotic pressure would be pointless.
Here are the main adaptations sand plants have contrived to live in these difficult ecological conditions.
It must be clear that every plant has contrived its own adaptation, which differs from any other, and of which very little is known. We can only list a few
examples:
● Succulence. A few plants have fleshy parts in which they store water, e.g.,
Cakile maritima, Calystegia soldanella.
51
53
52
Sea Spanish clover (Medicago marina)
Sea pancratium lily (Pancratium maritimum)
Hairiness. Leaves and juvenile twigs have thick hair covers which protect
plants from excessive transpiration, e.g., Medicago marina, Otanthus maritimus.
● Rhizomes crawling under the sand. Roots avoid high sand temperatures,
such as in grass types: Ammophila littoralis, Cyperus capitatus, Elytrigia
juncea, Sporobolus pungens. The culm base of these species is enveloped
by layers of dried-leaf sheaths, and this also prevents their overheating.
Echinophora spinosa, Eryngium maritimum, Euphorbia paralias and Pancratium maritimum (sea pancratium
lily) have a well-developed underground system, although they do not
belong to the grass family.
● Coriaceous leaves. Thick cuticles and
few stomata restrict water loss through
transpiration, as in Crucianella maritima
Eryngium maritimum, Salsola kali and
Echinophora spinosa.
● Annuity. Short vegetative periods are
temporal, rather than morphological
adaptations. Life is restricted to the
short winter-spring period, when it
rains more often and it is not excesThorny sea fennel (Echinophora spinosa)
sively hot. Examples are: Euphorbia peplis, Ononis variegata, Pseudorlaya
pumila (beach cocklebur), Silene colorata, Vulpia fasciculata (beach couch
grass). However, the most important adaptations are ecophysiological, i.e., the
ability to carry out processes in extremely arid and dehydrated conditions, of
which little is known.
●
■ Vegetation succession
Vegetation, as all living things, is an open, continually changing system, and is
therefore dynamic, not static. “Succession” occurs when, according to
McCormick, “…sites are characterized by differing phytocenoses (i.e., vegetal
groups) in temporal succession”. Vegetal groups alternate in well-determined,
not casual successions. Associations which usually alternate are called series
(e.g., the series from Cakile cover to maquis). Beaches are a classic example
for the study of successions: Kuhnholtz Lordat based his theory on the
dynamic binomial (or trinomial) and, in the 18th century Lancisi was the first
scientist who proposed “succession” as a scientific model. The succession of
beach vegetation is shown in the chart (see pag. 54).
Although this model clearly outlines the series from Cakile cover to maquis,
typical of the Mediterranean and Atlantic coasts, it is incomplete because it
only describes vegetation variations from the sea landwards. However, these
AMMOPHILA
ACCUMULATION/EROSION
CRUCIANELLA
AGROPYRUM
ACCUMULATION
EROSION
CAKILE
ACCUMULATION
WIND ACTION
VEGETATION BARE BEACH
VEGETATION
ACCUMULATION
54
Vegetation sequence in a beach-dune system
beaches feature all phases contemporaneously, and there is no explanation to
the temporal succession, i.e., if succession occurs in both space (from the
waterline landwards) and time, throughout the years. The situation is much
more complex. In order to have a clearer view of this situation, we may compare two models - synchronic and diachronic - which examine two different
aspects of this phenomenon:
● Synchronic. Vegetation examined at a given moment, as described by the
chart above.
● Diachronic. Vegetation examined over years, decades or centuries; e.g.,
very dynamic beach-dune systems may feature successions of different plant
associations over short periods. Actually, biological phenomena are cyclic and
also the examined succession may be related to this same model. Different
types of vegetation (which the synchronic model describes as fixed in their
positions) gradually move forward with both the changing of the seasons and
the passing of time (as long as there are no natural catastrophes or human
interventions). Eventually, there will be a new synchronic model identical to the
previous one, but resulting from a diachronic process lasting several decades.
Each year, vegetation grows, germinates, fructifies, some plants lose their
leaves, others dry up completely, and the following year this cycle starts all over
again, growth, germination, etc., but slightly forward, and then on and on, plants
move from one stage to the following, from one association to another. The
result is the synchronic model, but the process is intrinsically diachronic: if it is
explained only synchronically, its complexity is overlooked. The phenomenon
may sometimes be seen in its diachronic series. In the early 20th century, an
offshore quay was built at Punta Sabbioni, near Venice, to avoid the silting up of
the port. According to the maps of the period, the offshore quay projected
seawards on a 1-2 m deep bottom. After the construction of the quay, sand
accumulated on the eastern side. In 1950-52, botanical investigations revealed
that the beach had moved seawards for over 500 m, with regard to events of
1937-39. Today, the beach has moved seawards for more than1 km with regard
to 60 years ago. In this period, associations have indeed succeeded one another
as shown in the chart (previous page), but in disarray, alternating actions and
reactions. The diachronic model appears to be more realistic, although more
complex, but after all, life phenomena are all complex. Plant succession is
determined by gradual variations in substrate characteristics. When walking on
dunes, we have the impression of treading uniform sand, but precise chemicophysical analyses reveal significant differences which explain the subtle
variations in this environment. This volume does not provide detailed information,
but only a few data regarding the particle size of sand granules (see p. 46).
Beaches without vegetation contain coarse sand (diameters between 200 and
1000 µm), which is also found in the agropyrum vegetation. Marram grass grows
where sand grains are smaller; in scabious meadows and interdunal hollows,
most coarse sand is replaced by fine sand, the diameter of which is less than
200 µm. There are also variations in the microclimate (see chart below), and the
combination of these two factors identifies precise niches for each association.
40 °C
39 °C
38 °C
37 °C
36 °C
35 °C
34 °C
33 °C
32 °C
31 °C
30 °C
29 °C
28 °C
27 °C
26 °C
25 °C
24 °C
23 °C
22 °C
21 °C
20 °C
h 09
h 10
BEACH
h 11
h 12
h 13
AGROPYRUM
Temperature variations in a beach-dune system
h 14
h 15
h 16
AMMOPHILA
h 17
h 18
h 19
SCABIOUS
55
56
■ Origin of coastal flora
Evidence shows that coastal flora is very old: similar groups and adaptations
may be found on both sides of the northern Atlantic Ocean, Europe and North
America, suggesting that this vegetation already existed in the Tertiary, when
floristic exchange between the two continents was still possible. Some cases
are debated, e.g., the group Elymus farctus s.l. (including similar genera such
as Agropyrum, Elytrigia, Eremopyrum) concentrates in sub-desert areas of
central Asia, and several subspecies are distributed along the Atlantic and
Mediterranean shores. Chromosomes reveal that the Atlantic type is ancestral
and the Mediterranean species is the last result of this group’s evolution.
Also Ammophila have differing subspecies on Atlantic and Mediterranean
coasts, although here it might be a group of western origin. It is more difficult
to reconstruct the history of Juncus litoralis, which is closely related to J. acutus, a halophilous species usually found on saline soils. Instead, J. litoralis is
typical of interdunal hollows with brackish soils. It has long been considered
endemic to Italy (as J. tommasinii) and elsewhere confused with J. acutus.
These examples confirm that Mediterranean beach flora is quite recent, dating back to the Messinian - about 5 million years ago - and associated with
the continual variations in sea level during glaciations.
Beach flora does not feature many species: on the right, charts represent the
110 species of beach flora near
Venice. Analyses include biological
forms (i.e., adaptations to inclement
weather) and chorological types (geographical distribution of species). The
distribution of both biological forms
and chorological types varies greatly
with regard to all Italian flora. As
regards biological forms, beaches are
mostly colonized by annual and grass
species with underground organs.
The largest group is composed of
perennial grasses.
Chorotypes are more complex: there
are many Mediterranean (southern)
species in both Italy and Venice, but
there are few northern species on
beaches, although they are widespread in Italy. Instead, there are
more western and eastern species on
beaches than throughout Italy.
57
Percentage of biological components in beach
flora. Left: Venice; right: Italian flora
Pale blue: annual species; pink: grasses with
underground rhizomes; yellow: perennial
grasses; green: dwarf shrubs; brown: shrubs
and trees.
Percentage of chorotypes in beach flora. Left:
Venice, right: Italian flora
Pale blue: western species; pink: southern
species; yellow: eastern species; green:
northern species; brown: Eurasian species;
orange: cosmopolitan and exotic species.
100
90
80
70
61
60
49
49
40
35
26
20
0
1
1
PIONEERING
VEGETATION
Pungent rush (Juncus acutus)
3
2
AGROPYRUM
15
16
15
10
1
2
1
1
10
1
AMMOPHILA
SCABIOUS
INTERDUNAL
HOLLOWS
INTERDUNAL
HOLLOWS
COASTAL
WOODLAND
Variations of biological components in beach succession at Venice. Pink: annual grasses; blue: shrubs
and trees
Sandy shores and their animals
PAOLO AUDISIO
■ Life on sandy shores
As already mentioned in the previous chapters, animals find it hard to live in
sandy shore environments. There are many stress factors which affect the
survival of coastal zoocenoses, among which the most important are:
● Mobile substrates which vary in time and space: they are composed of
windblown sand which frequently covers small animals and their possible
food resources.
● Substrate aridity in dunes and exposed beaches, particularly during
summer, whereby sand granules cannot keep meteoric humidity, however
restricted.
● Beaches and sandy dunes lack nutrients, and therefore cannot provide
food for the small communities of primary producers and consumers.
● Saltiness both as salinity of water circulating or being absorbed by soils,
damp sand and deposits of marine organic matter, and chloride contents,
which are dissolved in the lower troposphere by means of marine aerosol or
crystallize on soils after surface dehydration, until rain dilutes or washes
thme away.
● Intense exposure to the sun, particularly in summer, combined with low
thermal capacity surfaces, i.e., easily overheated and quickly cooled;
coastal zoocenoses undergo temperature stress and circadian temperature
variations.
● High windiness and exposure to storms, which frequently and continually
move many animals both sea- and landwards, away from their natural
microhabitats. This increases their mortality rates and hampers reproduction.
● Typical fragmentation of these coastal habitats, for both natural (different
types of shores) and man-produced reasons, as well as their characteristic
position which stretches along a single axis, parallel to the sea/land line.
These conditions complicate the reproduction and diffusion of many
species, particularly small and highly specialized ones, which cannot
disperse actively and tend to die out locally. However, other abiotic factors
Footprints of a wild rabbit (Oryctolagus cuniculus) on dunes at Pachino (Sicily)
59
60
facilitate animal life, mitigating the usually difficult conditions and
contributing to the development of biotic communities, such as:
● The great thermal capacity of sea water, which mitigates summer aridity
and high temperatures, but also cold winter conditions, enabling many animals to reach atypical latitudes both south- and northwards, owing to the
favourable and stable temperatures of the coastal microclimate. For
instance, many thermophilous species of the Mediterranean area may
actively penetrate shores in northern Italy, relying on the thermo-regulating
influence of the sea, although they would not survive in continental areas,
where winters are colder. Likewise, mesophilous and hygrophilous organisms of central European plains (which colonized these areas during cold
periods of the recent Quaternary) may still survive at low latitudes in Italy
and its islands, particularly at the mouths of perennial rivers, where they
benefit both by summer thermo-regulation of sea water and hygro-regulation of river mouths themselves.
● The influence of sea motion, storms and river floods, which carry large
amounts of various organic matter (however intermittently and unpredictably),
Accumulated posidonia spheroids (phytobezoars)
particularly to areas near river mouths
or broad sea plains covered by
Posidonia.
Posidonia spheroids are produced by
the shredding of fibrous leaf residues
which envelope the large rhizomes;
when they fall off, they float on the
exposed beach backwash and
gradually form light brown, spherical or
oval felty masses technically called
phytobezoars. These conditions are
suitable for large and differing animal
species, especially invertebrates.
● The already mentioned protection
longitudinal bars and beaches offer
to terrestrial organisms which are
passively or almost passively carried
Posidonia rhizomes
over stretches of sea by currents,
winds and floods during storms and exceptional meteorological phenomena. This has enabled many species to spread and adapt themselves to
beach, dune and lagoon environments in Italy, even if they originally came
from far away (e.g., North Africa). On beaches near river mouths, after
spring and autumn floods, large numbers of terrestrial and aquatic invertebrates are carried seawards and stranded on nearby shores, where they
shelter under stranded vegetal debris for a few days or weeks. Particularly
euryecious species may sometimes survive for long periods and even
reproduce on the spot, thus integrating with the local coastal biocenoses.
However, most of these “castaways” die or actively and gradually disperse
inland.
Many biologists have noticed that sandy shore and desert environments are
very similar. Actually, resistance to high temperatures during the day and
the ability to move on mobile, windswept substrates poor in nutrients are
adaptations shared by both habitats.
It is also worth noting that, however negative salinity might be (which only
affects damp areas near the waterline or landward heathland periodically
flooded by the sea), other factors, such as the circadian and annual mitigating action of the climate, predictability of microclimates and food
resources, more extended vegetal covers and higher humidity, all make
beach environments less hostile than desert ones.
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62
■ Food chains of sandy beach habitats
63
Before analysing zoocenoses of sandy beach environments, we will examine
food relationships which link animals with other elements of coastal ecosystems. The figure below sketches the main connections between animals, plants
and soil microorganisms in hypothetical beach-dune habitats. Relationships
are simplified with the interconnection of three main food chains. The first food
exchange occurs between sea and land environments along the waterline, and
is associated with marine organic matter which is stranded on shores and constitutes one of the primary food resources for the entire ecosystem. Proceeding
landwards, the structure becomes more complex as dune vegetation diversifies
and is closely associated with stable soils. The strip of land from the waterline
to dune heathland is characterized by terrestrial food exchange and is associated with incursions of large predators (birds and mammals) which regularly or
occasionally patrol beaches and dunes in search of stranded organic matter
and small invertebrates which typically live in this area. Essential recycling of
organic matter is provided by remains of phytophagous organisms - sometimes
large biomasses such as pulmonate molluscs and their calcareous shells which supply the soil with nutrients and minerals.
Accumulation of calcareous shells of Theba pisana
■ Animal adaptations to sandy beach environments
MAINLAND
DUNE VEGETATION
BURIED ROOTS
GRAZERS
LITTER
PREDATORS
DETRIVORES
INTERSTITIAL FAUNA
DUNES
BEACH
MARINE DEBRIS · INTERTIDAL INVERTEBRATES
SEA
Many sand- and dune-loving invertebrates have contrived special eco-ethological adaptations to difficult and particular macro- and microclimate conditions of sandy beach environments. Typical adaptations deal with the frequently excessive exposure to the sun, e.g., many species have developed
enhanced burrowing activities in suitable substrates (damp sand, soil-sand,
silty sand), usually associated with other contrivances and morphological
changes in their burrowing organs - front legs in arthropods. Other animals
have shifted their circadian activities to the night (particularly in summer). A
few diurnal sand-loving species (e.g., acridid orthopterans), which are particularly suited to the warm and dry microclimate of sunburnt dunes, need to partially or totally burrow themselves in the sand during the night, both to hamper
the effects of lowering temperatures, escape nocturnal predators wandering
across dunes. Many less thermophilous species shift their annual reproductive
cycles to winter-spring or autumn, alternating them with long estivation periods (i.e., diapause or total inactivity during warm periods); others take advantage of daily or annual sheltering places or food resources and wander
between the waterline and dunes in search of food. Many species have contrived systems to avoid contact with overheated surfaces, such as long, taper-
ing legs and fast walking; insects fly swiftly and skim surfaces (to elude strong
sea winds) or, if they have lost their flying skills, they become brachypterous or
apterous (i.e., their supporting wings partially or totally disappear). Many dune
beetles have more or less spherical bellies and large cavities under their wingcases which have thermo- and hygro-regulating functions. Many of these
adaptations are identical to those of many invertebrates and small eremic
(related to deserts) vertebrates which have evolved in similar ways to withstand climatic and water strains and adapt to substrates. Many terrestrial
arthropods (particularly insects) have contrived special adaptations to halobious conditions, i.e., physiological modifications of their excretory organs, to
survive in highly saline environments which are normally hostile or inaccessible to non-specialized organisms. Other animals have resorted to simple
tegumentary adaptations (waterproof hairs and bristles, waxy coatings, etc.)
which protect wings and other delicate parts from the effects of partial or total
immersion in sea water. Many small dipterans and beetles of various families
are practically dry when leaving the water. Another common adaptation is
cryptic behaviour or colouring, i.e., animals’ ability to blend with the background through colour matching or shading. Typical are small yellow, white,
grey and black alternating spots, which perfectly mimic the colour of the sand
colonized by these species.
64
■ Types of habitats and zonation of animal communities associated with
sandy beaches
Scarites buparius
Let us now analyse the main types of habitats and zoocenoses of sandy beach
environments.
These are peculiar habitats, which include both marine benthic and terrestrial
or freshwater organisms which live between sea and land. Populations will
therefore have a double, overlapping origin, with terrestrial and freshwater
animal species (of stationary, watertable and interstitial waters) which have
adapted to brackish water and withstand immersions in the sea or burrow in
salty debris, and sea benthic, interstitial animals which have adapted to
brackish water and withstand exposure to the air and sun, in sufficiently damp
conditions. Despite the attempts of marine biologists, it is very difficult to
distribute the heterogeneous group of coastal organisms in planes or zones,
particularly those animals which live in sandy or silty-sandy substrates, where
communities overlap due to both the influence of various local abiotic factors
and the considerable circadian or seasonal vagility (mobility) of many species.
It is not surprising that, when treating fauna and biotic communities of shore
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66
environments, marine biologists adopt different terms to indicate the same
types of environments, or (even more confusing) call different types of
environments or their different aspects by the same names.
Zones are usually parallel or sub-parallel to the coastline and their width is
determined along their orthogonal axes. We prefer the word “terrace” to
“plane”, normally used by marine biologists, because “plane” regards vertical
ecological zonation, whereas sandy beach environments have fundamentally
horizontal zones and small, negligible altimetric and bathymetric variations.
1. The first terrace, which is usually narrow in Italian beaches - between a few
decimetres and a few metres - is called intertidal (or intercotidal), is constituted by sandy beach and is included between the minumum level of syzygial low
and maximum syzygial high tides. In the Mediterranean, variations between
low and high tide are very small, about 30 cm (there are a few exceptions,
such as in the Gabès Gulf in Tunisia, with 2-metre variations, or in the high
Adriatic, where they locally reach 1 m), and therefore, the width of the intertidal
zone depends on the gradient of the beach. The more inclined beaches are,
the narrower their terraces; the flatter and more slowly degrading seawards,
the wider their terraces, as in beaches of the high Adriatic. When bioclimatic
and biogeographical factors are equal, animal communities of wide intertidal
terraces are more stable, diversified and richer, whereas they are hardly present in narrow beaches. Intertidal communities of the English Channel and
North Sea are more abundant and stable, because variations between high
and low tide may reach a few metres and shores are flat. This area is called by
marine biologists the middle-shore (or intertidal) plane of sandy substrates.
These habitats are characterized by sea-deposited organic matter which is
continually stirred and removed by backwash or currents, and does not contain terrestrial vegetation. Various, elusive interstitial microinvertebrates
(mesopsammon - see pp. 70-71; as already mentioned, are complex communities, which are exclusive to aquatic environments, although living between
land and sea; they are not treated in this volume) live burrowed at different
depths in the sand. Communities which live on the surface of the intertidal terrace, in chiefly silty-sandy habitats, are composed of burrowing animals which
live on organic matter floating on these mobile substrates, and are usually
drifted by tide variations.
2. The second terrace, called eulittoral, covers the area between the upper,
landward limit of the intertidal terrace and the lower, seaward limit of the third
terrace, called supralittoral. The eulittoral terrace is traditionally called by Italian
and European researchers the lower, seaward margin of the supralittoral zone
of sandy substrates. The width of eulittoral terraces depends also on gradients
67
extralittoral belt
supralittoral belt
eulittoral belt
intertidal beach
Zonation of animal communities
in sandy shore environments
and types of beaches. These areas contain bare sand which is only
occasionally splashed by exceptionally high tides or storms. These phenomena
deposit animal, vegetal or algal debris of various kinds, origins and quantities
on sandy areas of medium gradients and normally totally bare. These areas
may be divided into lower seaward and upper landward eulittorals. The former
contain most of the smallest and lightest stranded organic matter, with usually
small masses (between a few grams and a few hundred grams). They have
therefore restricted inertia when carried by storming waves (e.g., the laminated
leaves of marine monocotyledons, small bits of wood, pumice pebbles, etc.),
together with coarser material (such as brown algae, dead sea vertebrates and
invertebrates) which are heavier and difficult to carry ashore by breakers.
Instead, the upper eulittorals contain material with low specific weight, coarser
and/or easily carried by currents (such as tree trunks, branches or logs carried
seaward by river floods). Sprouts of pioneer plants of supralittoral terraces are
often found in these landward areas, particularly in late winter and spring; they
are later swept away by storms or succumb to the stressful conditions of
substrates. In the past, marine biologists adopted the word eulittoral as a
synonym of middle- and intertidal, which must not be confused with its more
recent and present meaning. Bare, sandy intertidal and eulittoral terraces
68
colonized by organisms which have adapted to usually wet, damp and bare
sandy beaches, may also be called sandy madolittoral terraces (from the Latin
word madidus meaning wet, damp).
Bare, sandy eulittoral terraces contain small invertebrates associated with
stranded organic matter: “banquettes” of laminated leaves of marine phanerogams such as Posidonia and Zostera, large brown algae remains or sea animal
carrion, wood carried down by river floods, large pebbles, pumice deposits,
remains of terrestrial animals carried seawards, etc. Lower, seaward eulittorals
of the exposed beach as far as the upper, high-tide waterline frequently contain
saprophagous, detrivorous invertebrates and their specialized predators. Particularly near river mouths, animals stray from their usual habitats: aquatic, psammophilous organisms typical of rivers and continental lakes wander seawards,
and psammophilous, coastal organisms penetrate sandy river banks.
3. The third terrace is called supralittoral and may be divided into two parts,
one corresponding to landward-ascending sandy substrates, the other consisting of flat or slightly inclined silty-sandy substrates. The former may be
called the dry supralittoral of sandy beaches, corresponding to the foredune
(or embryo dune) area, which contains pioneer psammophilous vegetation.
This is the large sandy area between storm berms and the first dunes colonized by the first, sparse grasses such as sea-rocket (Cakile maritima) next to
the upper eulittoral or, landwards, sea holly (Eryngium maritimum), sea
bindweed (Calystegia soldanella) and beach grass (Elytrigia juncea). Breakers
might only occasionally splash these areas. The damp supralittoral with silty
beaches is characterized by silt, mud or fine, muddy sand rich in salt which
cover large, flat or low-gradient shores.
Here, particularly near river mouths and coastal lagoons characterized by
shrub-like vegetation, such as chenopodiaceae (Salicornia, Suaeda) and
halophilous, hygrophilous rushes (Juncus), occasional sea floods give rise to
saline or brackish pools. The supralittoral terrace of embyo dunes contains
more or less specialized phytophagous, flower-eating, indirect dune-loving
organisms (i.e., associated with psammo-halobious plants) and psammohalobious or ubiquitous direct dune-loving specialized detrivores and predators which are also distributed in continental sand environments. The supralittoral terrace of silty-sandy beaches is characterized by detrivores and predators usually found in large coastal plains or depressions, especially
halophilous, mud-loving invertebrates. These communities are very similar to
those of extralittoral silty-sandy shores of damp dune heathland and coastal
lagoons which contain stationary brackish and freshwaters.
4. All the other landward environments are contained in the large extralittoral
69
Banks of Posidonia
terrace which includes the first mobile dunes, consolidated dunes, dune
heathland and coastal lagoons of interdunal hollows. The first, seaward
extralittoral area contains unstable, wandering white dunes which are easily
modelled by strong winds and colonized by sand reed (Ammophila littoralis).
Proceeding landward are grey, consolidated dunes, which contain Crucianella
maritima, sea chamomile (Anthemis maritima), bird’s foot trefoil (Lotus
commutatus), beach lavender (Otanthus maritimus), everlasting flowers
(Helychrysum spp.), Silene spp., sea scabious (Scabiosa maritima), rockrose
(Cistus spp.), juniper (Juniperus oxycedrus) and sometimes ephedra (Ephedra
fragilis, E. distachya), rosemary (Rosmarinus officinalis), Teucrium spp.,
tamarisk (Tamarix spp.) and Ononis spp., together with other elements of
shrub-like maquis distributed on dune tops and dune heathland.
Supralittoral terraces of embryo dunes and extralittoral areas of white and grey
consolidated dunes form the sandy siccalittoral terrace (from the Latin siccus,
dry), which is followed by extralittoral dune heathland colonized by forests of
Juniperus phoenicea, holm oak (Quercus ilex), pines (Pinus spp.) and other
mesophilous undergrowth.
This volume does not treat the zoocenoses of these areas, which are usually
composed of hybrid, non-characterized populations of both Mediterranean
maquis and xerophilous or mesophilous plain forests, but only describes the
most frequent elements usually found on dunes.
70
Mesopsammon
The term mesopsammon refers to small
or very small interstitial aquatic fauna
which has adapted to life in hollows and
cavities, where water is slowly filtered
through the microscopic interstices
between sand grains and fine gravel.
Mesopsammon may be found in any
sandy accumulation, on the sea bed, in
the transition between land and sea on
sandy beaches, along the banks of
lakes and rivers, and even under the
bottom of lakes. Although they are
invisible, these little-known
environments may be found almost
anywhere.
However, the percentages of the main
taxonomic groups change according to
the presence, in interstices, of sea- or
fresh-water. In the former case, there are
mainly marine groups, such as
turbellarians, polychaetes, nemertines
and kinorhynchs, together with large
numbers of phyla such as cnidarians,
sponges, bryozoans, molluscs, or other
amazing organisms like microscopic
echinoderms and ascidians. In the latter
case, there are freshwater groups such
as oligochaetes, water-bears,
gastrotrichs and water mites, together
with small, pre-adult stages of aquatic
insects. Both types of waters contain
large numbers of protists, especially
ciliates, nematodes and many freshand seawater crustaceans (especially
harpacticoid copepods, isopods,
amphipods, moustache shrimps,
ostracods and others).
Obviously, sandy coastal environments
contain both types of fauna, and it is not
surprising that sand near the waterline
(the intertidal belt) is usually the richest
and most diversified in terms of total
numbers of organisms, species and
phyla. Almost all the animals which
Paolo Audisio
compose mesopsammon share similar
adaptations, such as extremely small
size (most are between 0.1 and 0.5 mm
long), very thin, tapering, flattened
bodies (even those belonging to groups
which usually have completely different
shapes), reduced or totally absent eyes,
no pigmentation, suckers to adhere to
sand grains, and other peculiar
modifications.
As they all undergo similar selection
(associated with their need to survive in
such particular substrates), they may
feature extraordinarily similar
morphologies and sizes which involve
both metazoans - true multicellular
animals - and unicellular protists, like
ciliates.
At variance with the division of trophic
roles which is typical of all animal
communities, most mesopsammon
feed on microscopic organic debris
filtered through sand and unicellular
algae (especially diatoms); some of
them prey on other microphagous
micro-organisms.
The mesopsammon of intertidal
environments and the many physical,
chemical and mineralogical factors
which affect their presence are very
complex. The parameters which most
influence environmental conditions are
the particle size of soil, its mineral
contents, the mean temperature of
filtering water and its salinity, quantity of
dissolved oxygen, the nature and
concentration of organic matter from
nearby rivers or watertable, the
absorption rate of sand in the various
layers, and its relationship with
exposure to sunlight at the surface.
The interrelation of all these factors,
particularly salinity and temperature,
gives rise to the usually euryhaline and
eurythermal nature of many
mesopsammon organisms. They may
tolerate great circadian, seasonal, or
generally periodical variations in
Gastrotrich of genus Thaumastoderma seen
from beneath (photo taken by SEM [scanning
electronic microscope] )
Harpacticoid copepod of genus Amphiascus,
lateral view (photo taken by SEM [scanning
electronic microscope] )
dissolved chlorides and temperature.
Many interstitial species migrate both
transversally (from the sea landwards,
and vice versa) and vertically (from the
surface downwards, and vice versa),
according to variations in temperature,
salinity and oxygen content.
The strongest discriminating factors are
usually the particle size of sand and its
mineral contents. Many species are only
suited to calcareous sand, others to
silicic sand, and the size of grains and
interstices may drastically influence the
presence of characteristic organisms.
Above and below particle size between
0.05 and 2 mm - typical of sand - i.e.,
when sand is replaced by silt, clay, or
gravel, there is no mesopsammon.
When the interstitial environment
contains coarse sand and
hydrogeological conditions are suitable,
there are frequent exchanges and
interrelations between interstitial and
other underground aquatic
environments.
Intertidal mesopsammon is often
composed of very interesting organisms
from the faunistic and biogeographical
viewpoints, as the evolution of many
species mirrors variations occurring in
the coastline, watertable and paleoclimate, because many species live in
fragmented, relict areas, or have
undergone extraordinary ecoethological and morphological
adaptations. Analysis of the biodiversity
of these organisms, which is still
incomplete, may provide an interesting
interpretation of Mediterranean and
Italian coastal ecosystems. This is a
further reason for protecting beaches
and underground waters from the
degradation caused by marine and
fluvial pollution.
71
extinction. As many psammo-halophilous invertebrates are very vagile and
many populations overlap, giving rise to complex combinations (in many Italian
regions which are already difficult to compare due to their different geomorphological, geographical and bioclimatic situations), they are divided into three
groups for an easier description:
1. Madolittoral communities include the intertidal zone of middle littorals, eulittorals of sandy beaches associated with stranded debris, those of landward, arid,
still bare areas, and those of sandy exposed beaches as far as embryo dunes.
2. Psammophilous siccalittoral communities, which are xero- and psammophilous organisms associated with embryo, wandering and consolidated
dunes, shrubs, dune heathland maquis and sandy fossil dunes.
3. Mud-loving supralittoral communities of large silty-muddy beaches (salicornia covers), and shore, psammophilous, mud-loving extralittoral organisms of
dune heathland and interdunal hollow lagoons.
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Dune covered with sea lavender (Otantus maritimus)
There may also be extralittoral terraces of fossil dunes (or paleo-dunes), i.e.,
originally coastal beach rock which was eroded by winds and storms and moved
landward following the seaward accumulation of sediments, thus extending the
original coastline a few hundreds of metres or kilometres seawards.
Beaches may also feature extralittoral terraces of dune heathland hollows next
to sandy, silty-sandy or muddy lagoon shores with their hygrophilous vegetation. This volume only treats communities associted with sandy shores of
coastal lagoons which are more similar to supralittoral salicornia meadows.
Extralittoral animal communities of white and grey consolidated dunes are
characterized by phytophagous species (especially rhizophagous, phyllophagous, and anthophilous, more or less specialized indirect dune-lovers),
but there are also detrivores and predators, usually direct dune-lovers and specialized psammo-halobious organisms, whereas there are only a few, occasional coprophagous, necrophagous and phytosaprophagous elements.
Extralittoral psammophilous communities of fossil dunes include mesoxerophilous elements associated with the variable plant cover of these habitats
(pine, holm oak, cork-oak forests and subcoastal, xerophilous shrubs), but also
psammobious or direct psammophilous, variably specialized elements which
have different trophic roles (especially saprophagous, coprophagous and rhizophagous).
Among them are many relict elements at both ecological and geographical
levels, with a few endemic species which live in restricted areas and risk
■ Fauna: invertebrates
The three types of communities above contain invertebrates which are here
divided according to significant or well-known taxa regarding the presence or
numbers of particular genera or species which are suited to coastal habitats.
In Italian regions, the recurring presence of naturalistically interesting elements
among these guide-groups is used to outline the quality of fauna in different
areas of sandy shores and provide suggestions for the protection of single
species, communities and ecosystems.
Bledius graellsi
Myosotella myosotis
Orchestia gammarella
Bledius eggs
Talitrus saltator
Tylos ponticus
Tylos europaeus
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74
Invertebrates: taxonomy
■ Communities of waterlines and
damp, sandy exposed beaches
(madolittoral)
Crustaceans
● Sand fleas. The European sand flea
(Talitrus saltator) typically colonizes damp
shores along the waterline, living in small
burrows, a few centimetre deep, in damp
sand. Other typical sand fleas are
common sand fleas (Orchestia
gammarella, O. montagui,
O. mediterranea, etc.) which are locally
abundant under deposits of stranded
algae and laminated Posidonia leaves.
When disturbed, all halobious sand fleas
hop in a distinctive way on the debris
accumulated by waves on the waterline.
Sand fleas
Paolo Audisio
Actually, sand fleas sometimes move far
from the waterline: for instance, during
the night, Talitrus saltator may reach
consolidated dunes at tens of metres
from the sea, exploiting an interesting
astronomical system of orientation.
● Isopods. Sand fleas often live with
other burrowing crustaceans, such as
the isopod Tylos europaeus and similar
genera. They colonize beaches
according to their particle size and
sandy-gravelly incoherent material.
Tylos europaeus, which is distributed
in European-Mediterranean areas, is
found where sand is fine, whereas
T. ponticus lives under pebbles and
coarser sand. During the night, these
crustaceans wander towards dunes in
search of food, just like sand fleas. In the
Mediterranean, stranded debris is also
colonized by many other saprophagous
and microphagous isopods which have
typical names, such as Halophiloscia
zosterae, H. tyrrhena, H. ischiana,
Armadilloniscus litoralis, Buchnerillo
litoralis and Trichoniscus halophilus.
● Decapods. Also crabs (branchiuran
decapods) are regularly found on
beaches, especially at dusk or on cloudy,
rainy days. The most common and
adaptable is Carcinus mediterraneus,
occasionally found in intertidal terraces
(middle littoral plane), but usually present
on rocky beaches and natural or artificial
shores near ports or river mouths.
Coleopterans. Coleopterans are the
largest faunal group of sandy beaches,
both in terms of numbers of individuals
and species (at least 500 of the 12,000
Italian species may be considered
exclusive, typical or characteristic
colonizers of these habitats).
The normally rigid and resistant
integuments which cover them are an
excellent adaptation in these hostile
terrestrial environments, aiding the
animal to survive, resist wear and tear by
sand and reduce loss of water from their
body efficiently.
● Ground beetles. Among ground
beetles, the large Eurynebria complanata
are the most significant indicators of the
biotic qualities of sandy beach
ecosystems in Italy.
These coleopterans, which are
distributed in both the western
Mediterranean and Atlantic sandy shores
of western Europe, typically occupy
landward areas of exposed beaches
(sometimes near wandering dunes) and
prey on sand fleas (particularly Talitrus
saltator). During the day, they are always
found under tree trunks and other
stranded woody material (in which, as we
will see later on, there may be larvae of
weevils and of the rare scarabs of the
genus Calicnemis).
When night falls, their frantic nocturnal
activity - sand fleas hunt near the
waterline - begins.
This species, which until a few years ago
was frequently found on the Tyrrhenian,
Apulian, Sicilian and Sardinian coasts, is
rapidly dying out due to sea pollution,
which affects its biological cycles
negatively, but particularly to continual
treading of sand and removal of large
woody residues (trunks and logs carried
by river floods which accumulate on
beaches).
In Italy, this species is now rare and is
only locally found in a few Tyrrhenian
(especially Tuscan) coasts which are not
Eurynebria complanata
visited by tourists and do not need
maintenance.
Among scaritine ground beetles, typically
found on damp beaches, are a few small
Dyschirius, especially D. numidicus, a
western Mediterranean halobiont species
which lives on sandy shores throughout
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Parallelomorphus laevigatus
Lophyridia littoralis
Italy, and Parallelomorphus laevigatus (in
the past called Scarites laevigatus).
These are medium-sized scaritines (1622 mm) associated with good
environmental quality beaches, where
they live near damp waterlines (lower
eulittorals). They walk on beaches even
in daytime, preying on sand fleas,
particularly Eurynebria complanata.
Another carabid which typically lives on
Atlantic and Mediterranean waterlines is
the now rare and localized Cylindera
trisignata, which in the past was more
abundant on Italian shores, particularly
near river mouths and small
watercourses. The distribution area and
populations of these swift predators of
halophilous arthropods have been
drastically reduced, particularly by man’s
activities, such as tourism, sand
quarrying and marine pollution.
Another species of tiger beetle is
Lophyridia littoralis, which colonizes the
same environments, but also dunes and
dune heathland, as far as many
kilometres inland. Its Mediterranean
subspecies littoralis is found on many
Italian shores. Hundreds of tiger beetles
of various species hunting on sandy
beaches on warm spring and summer
days, performing sudden, short and
grazing flights when disturbed (Linneus
called these beautiful coleopterans
“Insectorum tigrides veloces”), is now a
fading memory for most naturalists and
entomologists. On most Italian beaches,
large populations of tiger beetles are so
unusual, that they immediately attract the
attention of researchers, who cannot help
comparing this sight with memories of
only twenty or thirty years before. Larvae
of tiger beetles, which also prey on sandloving invertebrates, hunt burrowed inside
short, vertical tunnels in damp sand: it is
not difficult to imagine the consequences
of protracted treading by tourists or, even
worse, the passage of vehicles for the
cleaning of beaches, on these organisms
and their peculiar, fragile habits.
Tiger beetles, just like Eurynebria,
stenecious, anthropophobic predator
species, which are affected by even
minimal environmental changes, live in
locally quiet areas and are good
biological indicators of coastal
ecosystem quality. In Italy, their falling
numbers may now be interpreted as
population crashes.
● Rove beetles. Sand fleas and Tylos often
live with small, predator rove beetles of
the genera Cafius, Gabrius, Remus,
Phytosus, Medon and Heterothops, the
most common of which is Cafius
xantholoma, which is not particularly
affected by man’s presence. Other small
rove beetles, such as Polystomota and
Emplenota, feed on halophilous
dipterans, in the cocoons of which they
develop. Just like crustaceans of the
genera Talitrus and Tylos, also a few rove
beetles burrow vertical tunnels in damp
sand. Among them are a few species of
the genus Bledius, which are less than
1 cm long. The males of many species
usually have unusual thorn-like
extensions on their pronota and heads.
These species feed on microalgae, lay
their eggs in small lateral cells inside their
tunnels, and are often prey of small
burrowing ground beetles of the genera
Dyschiriodes (as mud-loving species
associated with silty environments,
described in the chapter about
invertebrates in salicornia meadows and
dune heathland).
● Hister beetles. The small, sand-loving
hister beetles are common
saprophagous organisms of the genera
Hypocaccus (they are about 2 mm long).
Their Italian species are often found on
stranded, dead, terrestrial and marine
vertebrates (especially fish), but they are
also attracted by excrements
of mammals (including
man’s). In Italy, typical,
widespread species are
Hypocaccus rugifrons, H.
brasiliensis and particularly H.
dimidiatus. Large numbers of
these coleopterans may be a
nuisance to sunbathing
tourists, who are tormented
by their continual flying and
landing. Another specialized
psammo-halobiont hister
beetle which frequently colonizes Italian
beaches, especially stranded deposits of
marine monocotyledons of the genus
Zostera, is Halacritus punctum (see
drawing), one of the smallest Italian
coleopterans (about 0.5 mm).
● Hydraenid beetles. These very small
coleopterans (1-2 mm) are typically
found in deposits of vegetal debris
splashed by water, (most species of this
family live as benthic lapidicolous
organisms in moving waters) and have
adapted to brackish and saline waters,
although they are not specialized to life in
coastal environments. Among them are a
few Ochthebius (O. muelleri, O. virdis,
O. marinus and others) and other species
are more frequently found in salicornia
meadows and on the shores of coastal
lagoons where they feed on
phytoplankton as we will see further on.
● Click beetles. In Italy, this family
includes a few hundreds of species,
mostly debris- and root-eaters. They
typically hop by suddenly clicking their
thorax muscles. Only one nocturnal
species, the pale yellow circumMediterranean pomace fly Isidus moreli,
less than 1 cm long, is often found in
summer under the stranded vegetal
debris on eulittoral terraces,
whereas its larvae develop on
grasses roots on dunes.
● Soft-winged flower beetles.
Together with malachiids and
dasytids are a large group of
coleopterans which normally
colonize flowers of grasses
and shrubs. Among species
associated with beaches,
the most specialized and typical
are Brachemys brevipennis,
small, black, wingless
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coleopterans, the short elytra (wingcases) of which are characterized by a
white spot. Their long, thin legs make
them look like ants. Although they are
usually found on sandy or pebbly
beaches, they may easily be washed by
water and also live in salicornia meadows
and brackish lagoons. They are
widespread in the Mediterranean. Their
rarer congenus Brachemys peragalloi,
which is more colourful (with red
prothorax), lives in similar environments
but is associated with narrower beaches
(western Liguria and southern Provence)
and risks extinction. Other beach-loving
species, usually found in stranded debris
along eulittoral terraces are malachiids
Colotes punctatus and Apalochrus
flavolimbatus and the dasytids
Dolichosoma lineare and Psilothrix
viridicoerulea.
● Antlike flower beetles. This group
typically walks on beaches and includes
large numbers of psammophilous
species, many of which are exclusive to
this environment.
The most common is Anthicus
fenestratus, found on all sandy shores and
dunes in Italy, where it wanders in search
of stranded debris and organic residues.
However, like many other antlike flower
beetles, it avoids man and its numbers are
gradually falling in tourist resorts. Among
the many Anthicus are A. brunneipennis,
endemic to Sardinian and Corsican
beaches, and the rare A. genei,
widespread in the Mediterranean, but
typical of small sandy beaches of rocky
coasts. The extremely long-legged genus
Mecynotarsus is also sand- and sealiving, like the common, very fast
M. serricornis or the rare M. fausti. Other
species are typically found in stranded
vegetal debris, particularly the infrequent
Amblyderus scabricollis, a western
Mediterranean species found on
Calabrian, Sicilian and Sardinian
beaches, where it apparently lives with
the similar A. brunneus, which is
probably endemic to Calabria and Sicily.
The same vegetal and algal debris also
hosts a few Endomia, such as the
common E. tenuicollis, which prefers
sun-dried deposits.
● Darkling beetles. Among specialized,
detrivorous coleopterans of beaches is
the family of darkling beetles. Many of its
species have adapted to life in hostile,
sandy environments, particularly desert
or sub-desert areas, and they are usually
found in dunes.
Italian eulittoral terraces are colonized by
many species of the small, chiefly
nocturnal Phaleria. Its yellowish members
share the same area of sandy beaches,
especially near stranded debris or
carrion, together with a few species of
Xanthomus, such as X. pallidus,
X. pellucidus and Halammobia pellucida.
They live with other, diurnal darkling
beetles, like Tentyria, Pimelia and Erodius.
Erodius siculus
The supralittoral and extralittoral
species of this family, just like sandloving arthropods, are active at night
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Phaleria acuminata
and move to eulittoral terraces near the
waterline. Then, during the day, they
shelter near dunes.
● Scarabs. Since most scarabs are
associated with dune environments, few
of them eat stranded sea debris. Among
these are a few dung beetles of the
genus Rhyssemus, Psammodius and
seldom, species of the genera
Pleurophorus, Platytomus and Diastictus,
which colonize moist, sandy beaches
near river mouths.
● Weevils. Three species of snout beetles
are typically found in stranded debris, the
unusual Styphloderes exculptus, a
western Mediterranean species which
prefers dry algae; Mesites pallidipennis,
with a peculiar, tapering, reddish body;
Aphannommata filum (in the past known
as Brachytemnoides filum), the body of
which is equally tapering but black. They
all live on stranded wooden debris (they
are xylophilous, i.e., they feed on wood).
Orthopterans. Most orthopterans live in
landward shore stretches, where leafand root-eaters feed on the more
abundant vegetation. However, a few
may colonize damp beaches. Hundreds
or thousands of locusts (both Italian and
African) typically “mass-drown” during
their frequent migration over sea
stretches swept by strong winds which
carry the dead bodies of these large
insects. They constitute an important
food resource for birds, foxes and many
small, zoosaprophagous invertebrates
(especially coleopterans). Although
usually found on pebbly beaches, the
cricket Paramogoplistes squamiger may
colonize pebbly-sandy shores.
● Earwigs. There is only one species
which typically, although not exclusively,
lives on stranded residues, the
uncommon Labidura riparia, found in
Asia, Europe and the Mediterranean (and
not, as is often thought, cosmopolitan or
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Anisolabis maritima
sub-cosmopolitan). It colonizes sandy
and pebbly marine beaches and banks
of watercourses and may migrate
upstream as far as inland valleys.
Another earwig which is typically, but not
exclusively found in stranded debris is
Anisolabis maritima which, just like
Paramogoplistes, prefers pebbly
beaches. Both species are dying out due
to man’s activities.
Neuropterans. Many species of
neuropterans live on sandy coastal and
sub-coastal environments. There are a
few species the active predatory larvae
of which move seawards to damp sand
and waterlines, particularly if sand is fine
and beaches are not visited by man.
Among them is Synclisis baetica, which
is widely distributed on Italian coasts.
Dipterans. May species of sea-loving
flies colonize sandy beaches, among
which are the genera Orygma and
Coelopa and particularly shore flies of
the genera Hecamede, Scatella,
Ephydra, and others. This important
family features many salt- and sea-
loving species which are more or less
associated with damp sand, where their
larvae feed on microalgae. They are
widely distributed on Italian beaches,
but also in coastal lagoons and marshes,
salt-mines, salicornia meadows or near
river mouths, such as Asmeringa
inermis, Hecamede albicans,
Homalometopus albiditinctus, Ephydra
bivittata, Scatella subguttata, Scatophila
modesta, etc. Other flies are typical of
waterline habitats, like Helcomyza
ustulata mediterranea and Fucellia
maritima, which usually colonize coasts
of the high Adriatic.
Arachnids. In the same environments,
under stranded residues, there are also
small, predatory false scorpions of the
genus Garypus and a few specialized
halophilous mites, such as
Hydrogamasus salinus. Garypus
beauvoisi is a Mediterranean species
living in Sardinia and recently found in
areas of the northern Tyrrhenian. It
colonizes algal and vegetal deposits and
seagrasses of lower eulittoral terraces.
It is one of the largest Italian false
scorpions, with a large, flat, stocky body
about 7 mm long. Also a few spiders
typically prey on small, sand-loving
arthropods found in stranded debris;
among these are a few phylodromidae of
the genus Tibellus, like T. macellus and
T. maritimus, which are often found on
grasses of dunes and dune heathland,
but also dwarf and jumping spiders
Other typical inhabitants of Italian
beaches are the members of the
psammophilous and predator family
Lycosidae (wolf spiders): Arctosa perita,
the congeners A. personata and A.
cinerea (especially near river mouths)
to walk swiftly, and they are perfectly
adapted to life on sandy shores.
Arctosa perita
and, in the same family, the more
common Alopecosa febrilis, A. cursor, A.
pulverulenta and Xerolycosa miniata.
Most Lycosidae are thermophilous and
variably psammophilous: they burrow
invisible tunnels in the sand and are
often found in dunes and dry, sunny,
sandy areas inland.
The colours of Arctosa, particularly
A. perita, A. cinerea and A. personata
mimic sand, their long legs enable them
Hydroschendyla submarina
Centipedes. Also halophilous,
predatory, geophilomorph centipedes
live under stranded debris, like
Geophilus poseidonis and
Hydroschendyla submarina, the names
of which already indicate their ecological
preferences. The former is found in the
Mediterranean as far as Somalia, the
latter is distributed in the AtlanticMediterranean areas as far as Sweden.
In Italy, they colonize Tuscany, the
Ponziane Islands, Campania and islands
around Sicily and Sardinia. Another
infrequent, halophilous, geophilomorph
centipede is Geophilus fucorum, which
lives in southern France, western Liguria
and northern-western Sardinia. Although
it is sometimes found in pine and holm
oak forests, it is typical of stranded
brown algae.
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