1 - Introduction
Maybe too often and most times faultily, man looks upon natural landscapes as if they were absolute and immutable entities; yet, the stateliness of mountains, the immensity of marine depths, the sweet harmony of hills, every physical and biological earth element, including the flora and fauna, undergo constant evolution. Some changes occur in geological periods only, others in briefer perceptible lapses of time: in a few years, a season or even a few seconds.
Italy is a relatively small-surfaced nation; besides, most of its territory is covered with mountain chains that do not always favour anthropic settlements.
The large extent of mountainous areas fosters the concentration of human activities in hilly, plain or valley regions sometimes presenting geological and hydrological features unfavourable to a permanent settlement; hence residential and productive centres are mainly located in very small areas with a consequent high anthropic pressure.
2 - Italy: an instance of geomorphologic instability
The current configuration of Italian territory is marked by frequent alternations of plain, mountain or hilly landscapes and deep rift valleys in a relatively small area. These result from the superimposition of morphogenetic processes, still active in the country and other Mediterranean regions with often devastating aftermaths, which have taken place in the last million years.
Our mountainous regions, particularly the Alps and Apennines, were moulded in the course of different but relatively recent times. Very old rocks, formed in different environments from those in which they are present now, were involved as from some 60 million years ago in that series of phenomena bringing about one of the highest among European chains: the "Alpine" orogeny. Thus, the frame of some present-day Italian regions, for example of Sicily, Apulia, Abruzzi, Campania, Trentino, Venetia or of Mediterranean areas such as Morocco, Algeria and Greece, that corresponded about a hundred million years ago to ocean shelves covered with a seawater stratum dating back to the primitive Thethys, was involved in the collision of the African and Euroasiatic shelves. The compressing movements between these, made more complex by the supposed in-progress formation of new ocean crust in the Tyrrhenian and east Mediterranean seas, allowed the folding, translation and overlapping of pre-existing imposing rocks to form mountain chains that from Sicily reach the north-east border of our country. During these big collisions enormous strains are produced; when the rock resistance is no longer able to contrast them, these give off energy causing an earthquake. Strains frequently provoke long and deep clefts ascended by masses of incandescent material, often followed by a seism, that come from the core of the earth and arrive to the surface with big eruptions creating volcanic buildings.
To the effects of endogenous agents, those brought about by exogenous elements must be added. A great deal of the Italian peninsula consists of mountains and hills; channelled or wild waters, glaciers and the sea itself easily corrode the rocks of more or less steep, already weathered slopes. The quick erosion of brittle rock versants of many regions, that at times gives rise to the phenomenon of denudation, is encouraged by other factors characteristic of the morphoclimatic Mediterranean area such as high precipitations and the alternation of dry and rainy periods.
Moreover, although with noble intents, man alters and destroys natural vegetation, intensifies and deepens ploughings or quits the country, he hollows out river-beds and seashores, builds canals and highways, industrialises, urbanises and impermeabilizes vast surfaces with cement avalanches, he dikes and controls watercourse flow-rates, creates artificial basins and weirs in the coastal strip that alter the normal flowing in rivers and along the coast of those natural materials normally supplying beaches.
3 - The coastal space
The coastal space whose equilibrium depends on a series of natural and anthropical factors must be considered in the whole complex body of those parts that have always attracted man since they offer the best conditions for permanent settlement: river basins, littoral areas and inshore sea. The anthropic pressure is therefore more evident on them.
These three physiographic elements are strictly linked to one another in their evolution concerning lithotypes, shapes of the floating belt and of the continental shelf, hydrologic features and consequently sediment supply, vegetation, weather and sea conditions (tidal magnitude, direction and intensity of the waves and ocean currents) and benthos living in the sea depths. Already naturally difficult, these relationships have gradually become more and more intricate owing to a coastal urbanisation that reached its peak with the building and tourist boom in the last 50 years but that had already begun with the diminished dangers coming from the sea and the reclaiming of malarial regions. Natural phenomena have been further complicated by human activities such as uprooting of silt to be used as building material, extirpation of vegetation and destruction of coastal dunes both due to building and draining of freshwater beds, subsidence following absorption of fluids such as water itself, gas and fuel oils, removal of river solid sediments, building of harbours and backup facilities as well as dredging of the sea-floor that eliminates the offing bar (an element which helps reduce the energy of waves) and kills plant and animal colonizations which stabilize the seascape.
The coastal space is the zone directly connecting the dry land to the sea which are profoundly different from a physical point of view; consequently it results from a temporary prevalence of either natural or anthropical morphogenetic processes operating at different degrees and times in the sea and on the firm earth. The coastal space must be considered as being composed of a floating littoral strip more or less large according to its orographic features (linked to the size of the hydrographic basins pressing on it) and of the inshore sea extending from the water's edge as far as the sea bed which reflects traces of the swell.
Due to its extent and vulnerability, Italian coastal space is a highly-endangered environmental territory; still more so if the nation is framed within the Mediterranean physical system where toxic dumps, oil slicks and barrels of tetraethyl lead find no definite boundary marks but an excellent and equitable spreading system: ocean currents.
4 - Pollution
The Mediterranean is a closed sea connected to the Atlantic Ocean by the sole threshold of Gibraltar; the total exchange of waters from this very narrow bottle-neck would, thus, require something like 100 years.
Minor connections occur with two more basins of limited extension themselves: the Black Sea through the Dardanelles, The Sea of Marmora and the Bosphorus and with the Red Sea through the artificial Suez Canal. Although of little importance as for water metabolism, the Mediterranean is considerably valuable from a biogeographical point of view: as a matter of fact, many tropical species have been brought into it on the wake of transiting ships.
Italy might be considered a natural bridge linking Africa and Europe and dividing the Mediterranean into two basins (Pct.1): the west one from the Sea of Alboran to the Tyrrhenian, and the east one from the Ionian and the Libyan Seas as far as Asian coasts. In these and generally also in smaller watersheds, circuits of anticlockwise ocean currents can be detected that spread polluting objects along every coast: any item floating in the Mediterranean sooner or later lands on one of them. This is still more worrisome if we remember that the exchange of Mediterranean and Atlantic waters occurs through the spit of Gibraltar where ocean currents flow on the surface; so only a small amount of floating wastes can pass through there. Oil tankers often discharging contaminated waters during their normal navigation happen to be one of the biggest threats to the marine environment; if one of them should sink, it would pour hundreds of thousands tons of crude oil into the sea. The floating part will sooner or later reach the coast; the heaviest one will sediment on the bed creating a lifetight carpet. The running costs of these sea monsters mean that careening and maintenance periods are reduced to the absolute minimum; in this way decades-old oil tankers kept together only by oil foulings sail all over the world. In some areas of the Mediterranean their navigation has been banned; yet just a few know that in the same sea there are two official areas where waters used to wash naphtha tailings off tanks can be legally emptied.
But the most dangerous form of pollution is not caused by floating materials; unfortunately all of us can notice it by walking along our beaches in winter and witnessing how many victims it produces among those turtles and cetaceans that eat plastic mistaking it for tempting jellyfish or savoury fish. The contamination produced by dissolved substances that penetrate in the trophic pelagic chain and by particles reaching the trophic nets which settle on the debris is much more devastating.
It is necessary to underline that sewage and contaminated waters of coastal countries have been discharged into the sea for centuries; if this was tolerated by the environment when only small seaside villages existed, it is no longer acceptable now that the coastal belt is burdened with the pressure of big urban areas and of seasonal tourism estimated at some millions of visitors per year all over the Mediterranean. Tourist areas are seldom connected to purification plants and most times sewage waters are poured into absorbing wells often very close to freshwater beds. It is even more worrying that town or urban settling drainage systems still discharge directly into the sea.
Last but not least there is the contribution of industries many of which are situated along coasts and water-courses. Perhaps the mostrelevant aspect is the discharge of chemical wastes reaching the sea and trophic chain through the innumerable waterways gathering big quantities of discards from industrial plants. It is not by chance that in the last report on environmental conditions drawn up by the Ministry for the Environment, among the areas considered to be a hig risk there are the Bormida Valley and the Lambro Olona basin, tributaries of the Po river and consequently affluents of the Adriatic (Pct. 2).
Furthermore, waterways convey into the sea most nitrogenous and inorganic fertilisers, pesticides and insecticides that farmers employ to improve the yield of their allotments; in the Apulian inshore sea, for instance, the amount of pesticides is twice as high as those detected in other Mediterranean coasts.
Fishing exerts a very strong pressure on the sea fauna owing both to the quantity and quality of fishing fleets (as well as to the more extensive use of sonar to find big shoals of pelagic fish and the increase in the number of ships flying non-Mediterranean flags). In addition, there is the continual use of old methods: trawls, night fishing and drift nets or even explosives cause the destruction of the sea-floor, the indistinct annihilation of unsaleable species as well as of adult and young specimens that were not able to reproduce.
Furthermore, indiscriminate coral fishing, the acts of vandalism of those young underwater fishers who kill hundreds of young, small catches and those of inshore anglers who cover and plough the reefs with dozens of kilometres of lines and kilos of left behind sinkers must be remembered too. The intervention of tourists is not less important than that of fishers; the hundreds of motor and even sailboats are guilty of continually ploughing sea-beds where everything has been upset with their anchors.
By introducing tons of land and cement into the sea, the building of harbours and airports kills ocean Posidonia, already endangered by ships' and pleasure crafts' anchors. This is a plant growing between 0 and 40 ms in depth that, besides producing enormous amounts of oxygen through its stalks and roots, contributes to create underwater forests which function as deposit and reproduction sites as well as a nourishing source to many marine species. This sea-grass is particularly sensitive to changes in environmental parameters such as turgidity, luminosity, temperature and salinity. Moreover, as much as all benthic populations, ocean Posidonia plays a remarkable role in the protection of coastal strips; thanks to its radical structure formed by an extremely thick network of rhizomes and roots, it tends to stabilise and keep in check the sandy bottom on which it sprouts. Huge heaps of ocean Posidonia dead leaves, commonly found on our beaches at the end of their living cycle beginning from the second half of August onward, help detain the sand and protect seashores. Its uprooting and consequently the cleaning of beaches in certain periods of the year, by eliminating an obstacle, contributes to increase the effect of the swell and to remove the sand from the coast during the ebb.
5 - The anthropic impact
The present dynamics of coasts is only partly influenced by natural evolutionary phenomena; a decisive role is played by man both directly on the coastal environment and indirectly on those connected with it. Nineteenth-and-early-twentieth-century littorals still displayed shore contours noticeably moving forward maybe also as a result of big amounts of materials that surface scouring, facilitated by an intense deforestation, drained into the sea. Two dangerous and uncontrolled phenomena have appeared since the end of the first world war: the urbanisation of littoral belts and interferences in river basins.
In the first case an incessant demographic movement has come about toward the coastal belt where the population has steadily increased reaching a density of 395 inh./sq. km. as compared to the previous national average of 187 inh./ sq. km.; the community living along the coasts augmented by approximately 4,5 million inhabitants in the course of about forty years from 1951 to 1991. At the same time the physical pressure due to the increased number of mainly tourist and seasonal houses has consequentially increased the amount of uncontrolled sewage tippings in the sea or water-bearing strata. In some regions the percentage of untenanted dwellings exceeds 50 % if compared with that of the total number of houses in a town ( Liguria: 72,5 %; Sardinia 60,4 %; Calabria 61,3 %).
Coast anthropization occurs following the same patterns on all sandy strips (Pct. 3): building on the first beach ridge, the closest to the sea, extraction of building aggregates from the seashore, eradication of the submerged sandbank vegetation through access hollows to the sea (Pct. 4). In this way the rapid erosion of dune-bars provokes the lack of supplies to the beach and back-shore areas more easily flooded by surges owing to the destruction of one of the chief reservoirs. The construction of sometimes unauthorised minor works along the beach that had naturally formed there to absorb the energy of the sea quite often exposes them directly to meteomarine agents.
Many natural calamities stem from single individuals', builders', technicians' and administrators' carelessness or, worse yet, of the underrating of risks. The need to stunt the anthropization effects in these areas, that generally appears with significant seashore backward motions, is faced with the implementation of transversal or parallel protection works that, stopping sediments, alter the original coast contour. Thus, also big industrial or small tourist harbours interrupt the natural longitudinal flow.
Urbanisation concerns expanses of rocky coasts too. In the case where these are flat and generally steady, the urbanising phenomenon takes place through cementation of more or less large areas; this implies a fall in solid adrift deposits ensuing from the erosion exerced by the sea and by meteoric leaching. The situation of cliffs is much more serious; the erosion capacity of the sea is contrasted or enhanced by the rock structural and mechanic features, by the shoal morphologic characteristics and lastly by meteomarine conditions.
The presence of almost vertical surfaces and so of steep sea-floors at the foot of craggy cliffs, of a large fetch and of little coherent rocks facilitate the underwashing at the base which causes subsequent collapses with average backward movements estimated at some tens of metres per year.
Support and stabilisation works of coastal spits, characterised by cliffs quickly going backward, often made necessary for the safeguard of residential or, worst still, of industrial centres, result in two kinds of negative effects. If the intervention aims at protecting rugged cliffs with cement strata or backup works, solid supplies are stolen from the sea that must therefore be included in the overall scrutiny of the concerned seashores. In the case where the interference occurs even through bonding transversal or parallel support works (either groynes or reefs), artificial obstacles to sediment flowings along the coast and a consequent decrease in supply to inner breakwater beaches are created. Often parallel backups cause the partial enclosure of sounds within which water exchange is no longer guaranteed; the final result is the undesired rearrangement of the coast with a further alteration of the landscape and the sea ecosystem.
Water-courses are no longer able to carry large sediments to the sea because of a series of reasons: the building of weirs blocking water flowings as well as their deposits; the diminished liquid rate due to the use of water for irrigating, drinking and hydroelettrical purposes; hydrologic protection actions ranging from flow-rate controls to shore conservations in some cases made necessary following wrong settlings of residential and industrial areas or highways; reclamations by alluvion; huge concrete pavings of urban topographic surfaces urban; and aggregate uprootings from sea-beds for building purposes.
Yet, in other cases we must acknowledge that water-courses may have attained such a stage in their morphological evolution that the sediment they carry is too fine and, rather than being absorbed by the coastal drift, is pushed in the open sea where it settles in steep plains, beyond the shelf break.
6 - Changes in the sea level
An aspect that is often neglected when examining topics concerning the coastal space is the sea level. It is not steady in time but changes according to the increase or decrease in masses of water available on the planet; these, in turn, vary according to the alternation of world-scale phenomena regulated by the earth millenary motions: glaciations.
As the earth average temperature goes down, the ice volume increases and water mass diminishes; in warmer periods, the interglacial eras, a part of the ice-caps melt causing a growth in the bulk of available water. We live in an interglacial period now in which the sea level is rising, after being about 120 ms deep more or less 21,000 years ago. According to the most recent data coming from fixed stations spread with sufficient density at least in the north hemisphere maritime areas, the average increase of the sea level is estimated at about 1,5 mm/year.
It was lower at the end of last century and it seems that it has considerably gone up from the second half of the present one, certainly also in relation to the increase in the average temperature due to the greenhouse effect provoked by gas emissions into the atmosphere.
The rising of the sea level is not even; since ice-caps are the main water source, to an increase in the world average temperature corresponds a sort of "wave effect" propagating from ice-caps to the equator. Thus, more or less evident differences can be attributed for example to the size of basins, weather conditions, epirogenic movements as well as to gravity and centrifugal forces. In practice, the principle of the communicating vessels that the sea tends to satisfy is contrasted by a series of conditioning factors.
That the sea level tends to go up is not certainly something new in the earth's history; if some doubts still exist on the fact that the sea has gone beyond its present position in very recent times (in fact several authors maintain that it took place 6500 years ago during the Holocene Climatic Optimum), it is sure however that 125000 years ago, during the so-called "Tyrrhenian" interglacial period immediately prior to the last glaciation, the Würm, the sea reached a position of more than 6 metres above its present level in one of the three recognised fluctuations (Pct. 6): but those were absolutely natural swings!!
7 - The situation of italian coasts
The Italian peninsula has a coastal extent of about 7500 km; studies carried out by the Department of Earth Sciences of the University "La Sapienza" in Rome show that some 4250 Km of it are represented by rocky coasts and so about 3250 Km by sandy beaches 32% of which is under erosion and only 5 % is growing; 63 % can be considered steady even if about 10 % corresponding to beaches which are stable only thanks to unnatural supporting works should be subtracted from this percentage. Molise and Basilicata reach 74 % and 67 % of coasts moving backward respectively; on the contrary Sardinia, characterised by the least manipulated littorals, is the Italian region with less erosive problems.
An attentive examination of the coastal space of the Italian peninsula points out some situations which illustrate the general alteration brought about by anthropic activities.
The Tyrrhenian, Sardinian and north Sicilian coasts stretch for about 3500 Km. About 45 % of this expanse is represented by sandy beaches, 39 % of which is drawing back. On this side of Italy erosion is particularly evident along all the branching deltas. The mouth of the Arno in Tuscany, that had already displayed relevant backward phenomena owing to extended reclamations during the Renaissance, has significantly changed since the beginning of this century.
Along its right bank, the backward motion is at present estimated around 10 m/year.
On the contrary, at the mouth of the river Magra, a remarkable growth of its delta can be observed following the interruption by law of aggregate extraction from its bed. However, the harbour of Marina di Carrara has impoverished and moved back the littorals south of the port stopping the coastwise flow of sediments carried to the sea by the river itself.
Several tracts of coast are in artificial resettlement due to the presence of specifically planned backup works; although reducing the erosive effects of surface-running waters, these have brought about deep-running water erosive phenomena. At its outlet the Tiber, where an inner breakwater was built between the 30's and 40's in order to protect Rome from alluvial risks, is undergoing nearly a one-metre moving forward of the delta apex.
A great deal of the Domitio coast north of Naples, into which the Volturno, one of the most polluted rivers in Italy, debouches, has a natural coast-line altered by the constant presence of some tens of kilometres of tourist settlements and landing sites.
The Ionian and Sicilian coasts facing the Canal of Sicily stretch for about 1400 km. Apart from the beaches of Calabria for which a substantial growth or at least a situation of equilibrium is documented from the second half of last century, seashores in this part of Italian coasts are almost all undergoing erosion. In some places, for example in the Gulf of Taranto along the wide sickles north and south of Gallipoli, the sea has reached and eaten into the dune base which is also intensively deteriorated by the phenomenon of illegal building.
Along the pebbly and sandy coasts of Lucania, considered in rearrangement between the end of last century and the 50's, a remarkable backward motion, that also in this case corroded the foot of the dune, is noticed; this stems from the heavy uprooting of aggregates from river-beds and the seashore itself as well as from the high number of artificial basins situated along its water-courses; more worrying is the erosion of underwater seashores whose dynamics is influenced by the impoverishment of the ocean Posidonia layer and surely by the proximity of numerous underwater canyon heads feeding the deep Valley of Taranto.
The situation of rocky coast expanses is also significant; where they do not present very tough lithotypes, they show considerable backward motion phenomena; take for instance Capo Colonna near Crotone where only one of the Dorian columns of the Hera Lacinia temple and the ruins of large Roman imperial villas remain, or the condition of a few High Medieval antipirate sighting turrets lying edge-wise on the Gulf of Taranto along the Salento coasts; lastly at Punta Rondinella near Taranto again, along the coastal tract moulded in the brittle quaternary "benches", a Neolithic village is already mostly eroded by the sea and at Porto Perrone Roman imperial villas are lapped and demolished by sourges.
Adriatic coasts stretch for about 1260 Km. The upper Adriatic littorals show evident backward movement marks also ascribable to the spreading of reclamation works on alluvial strips behind the coastal dune. The situation of the Po delta is particularly interesting since works altering even its natural forms were started as far back as 1600. Also in this case the extraction of aggregates along the lower Po is of great importance: between 1951 and 1980 it was so massive that it can be compared to tens of years' solid supply to the coast.
Other situations of clear imbalance can be noted along the coast of Abruzzi and Marche where in order to protect the railway network man had to resort to parallel, longitudinal, transversal, submerged or half-submerged, surface, floating or even permeable backup works that, besides drawing almost everywhere an artificial coast-line, have dramatically changed natural environments. Remarkable backward movements must be also reported both north and south of the Gargano promontory owing to the decreased solid supply of the short Apennine watercourses. North-west of the Gargano some backward movements of beaches for some tens of metres have been detected over the course of fifty years. At the mouth of the Ofanto, erosion caused the eating away of 12500 sq. m. of seashores. Instead, the harbour of Margherita di Savoia has thwarted the south-northbound coastwise drift, in such a way that the surface contour has moved forward some two hundred metres whereas the deep-running water rock has considerably gone backward as far as to Siponto, just south of Manfredonia.
Relevant rocky coast backward phenomena must be reported near Bisceglie north of Bari where several dwellings have been endangered and man has had to resort to backup cementation and along the coasts of Monopoli south of the Apulian chief-town . Further south of Brindisi, near the new coal-power plant of Cerano, whose cliff is protected by parallel outer breakwaters, of the Medieval Torre Mattarelle built (but it was about the mid-fifteenth century!) near the edge of the craggy coast only the south-east ridge remains.
A particular phenomenon involving some Italian coastal areas is that of the subsidence concerning both floating lands and the sea-floor. In the area around Ravenna, in the lower Po Valley and in the coastal strip near Pisa, the effects of coastal imbalance are made worse by the drawing down of the topographic surface due to both natural compaction of delta deposits and water-bed draining as well as removal of gas and natural fuels. Lowerings of 10 cm within fifteen years, between 1952 and 1969, have been reported near Venice; of 34 cm from 1970 to 1980 near Ravenna and of 1 m. in 30 years between Modena and Bologna. On the Tyrrherian coast, subsidence is estimated at about 30 cm in Pisa, toward the mouth of the Arno.
8 - Conclusions
From what has been written so far it is evident that the coastal space is a physical system whose evolution is influenced by delicate geological, morphological, meteomarine and biological equilibria that need to be taken into account also in those areas apparently unconcerned and far from the sea. The coastal landscape, however varied and smooth, is made of morphological and biological elements strictly linked to one another in an endless chain: deep sea-beds to submerged beaches covered with grasslands of ocean Posidonia, and from these to back-dunes or again from deep sea-floors to the talus and high cliffs. The evolution of the coastal space is therefore influenced by each of these elements; the alteration of one of them sometimes modifies the others irreparably.
The present situation is not at a point of no return; although not good, the health of the coastal space is not hopeless yet. There are highly deteriorated and perhaps condemned areas, but also many others that can still be saved and even become cornerstones of a profitable and clean economy. The cost caused by investments aimed at taking steps to restore the previous equilibrium is undoubtedly high; the possibility that comes up is to save an environment essential to human life and the advantages could easily exceed the drawbacks. Otherwise it might well happen that the next generations, our grandchildren, will put up plastic (maybe not even regenerated) castles on seashores.
Pct. 1 - Diagram of surface currents in the Mediterranean Sea
Pct. 2 - Location of geographic areas environmentally endangered.
Pct. 3 - Sketch profile of a sandy seashore.
Pct. 4 - Evolutional outline of an intensely anthropized sandy coast.
Pct. 5 - Evolutional diagram of a cliff.
Pct. 6 - The changes in the sea level during the Holocene.