Mediterranean Sea

TheMediterranean Sea(/ˌmɛdɪtəˈreɪniən/MED-ih-tə-RAY-nee-ən) is aseaconnected to theAtlantic Ocean, surrounded by theMediterranean Basinand almost completely enclosed by land: on the east by theLevantinWest Asia, on the north byAnatoliainWest AsiaandSouthern Europe, on the south byNorth Africa, and on the west almost by theMorocco–Spain border. The Mediterranean Sea covers an area of about 2,500,000 km(970,000 sq mi),representing 0.7% of the globaloceansurface, but its connection to the Atlantic via theStrait of Gibraltar—the narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates theIberian PeninsulainEuropefromMoroccoinAfrica—is only 14 km (9 mi) wide.
Geological evidence indicates that around 5.9 million years ago, the Mediterranean was cut off from the Atlantic and was partly or completelydesiccatedover a period of some 600,000 years during theMessinian salinity crisisbefore being refilled by theZanclean floodabout 5.3 million years ago.
The sea was an important route formerchantsand travellers of ancient times, facilitating trade and cultural exchange between the peoples of the region. Thehistory of the Mediterranean regionis crucial to understanding the origins and development of many modern societies. TheRoman Empiremaintainednautical hegemonyover the sea for centuries and is the only state to have ever controlled all of its coast.
The Mediterranean Sea has an average depth of 1,500 m (4,900 ft) and the deepest recorded point is 5,109 ± 1 m (16,762 ± 3 ft) in theCalypso Deepin theIonian Sea. It lies between latitudes30°and46° Nand longitudes6° Wand36° E. Its west–east length, from the Strait of Gibraltar to theGulf of Alexandretta, on the southeastern coast ofTurkey, is about 4,000 kilometres (2,500 mi). The north–south length varies greatly between different shorelines and whether only straight routes are considered. Also including longitudinal changes, the shortest shipping route between the multinationalGulf of Triesteand the Libyan coastline of theGulf of Sidrais about 1,900 kilometres (1,200 mi). The water temperatures are mild in winter and warm in summer and give name to theMediterranean climatetype due to the majority of precipitation falling in the cooler months. Its southern and eastern coastlines are lined with hot deserts not far inland, but the immediate coastline on all sides of the Mediterranean tends to have strong maritime moderation.
The countries surrounding the Mediterranean and its marginal seas in clockwise order areSpain,France,Monaco,Italy,Slovenia,Croatia,Bosnia and Herzegovina,Montenegro,Albania,Greece,Turkey,Syria,Lebanon,Israel,Palestine(Gaza Strip),Egypt,Libya,Tunisia,Algeria, andMorocco;CyprusandMaltaareisland countriesin the sea. In addition,Northern Cyprus(de facto state) and twooverseas territoriesof theUnited Kingdom(Akrotiri and Dhekelia, andGibraltar) also havecoastlinesalong the Mediterranean Sea. The drainage basin encompasses a large number of other countries, theNilebeing the longest river ending in the Mediterranean Sea.The Mediterranean Sea encompassesa vast number of islands, some of them of volcanic origin. The two largest islands, in both area and population, areSicilyandSardinia.
TheAncient Egyptianscalled the Mediterranean Wadj-wr/Wadj-Wer/Wadj-Ur. This term (literally "great green") was the name given by the Ancient Egyptians to the semi-solid, semi-aquatic region characterised bypapyrusforests to the north of the cultivatedNile delta, and, by extension, the sea beyond.
TheAncient Greekscalled the Mediterranean simplyἡ θάλασσα(hē thálassa; "the Sea") or sometimesἡ μεγάλη θάλασσα(hē megálē thálassa; "the Great Sea"),ἡ ἡμετέρα θάλασσα(hē hēmetérā thálassa; "Our Sea"), orἡ θάλασσα ἡ καθ’ ἡμᾶς(hē thálassa hē kath’hēmâs; "the sea around us").
TheRomanscalled itMare Magnum("Great Sea") orMare Internum("Internal Sea") and, starting with theRoman Empire,Mare Nostrum("Our Sea"). The termMare Mediterrāneumappears later:Solinusapparently used this in the 3rd century, but the earliest extant witness to it is in the 6th century,inIsidore of Seville.It means 'in the middle of land, inland' inLatin, a compound ofmedius("middle"),terra("land, earth"), and-āneus("having the nature of").
The modern Greek nameΜεσόγειος Θάλασσα(mesógeios; "inland") is acalqueof the Latin name, fromμέσος(mésos, "in the middle") andγήινος(gḗinos, "of the earth"), fromγῆ(gê, "land, earth"). The original meaning may have been 'the sea in the middle of the earth', rather than 'the sea enclosed by land'.
Ancient Iranianscalled it the "Roman Sea", and inClassical Persian texts, it was calledDaryāy-e Rōm(دریای روم), which may be fromMiddle Persianform,Zrēh ī Hrōm(𐭦𐭫𐭩𐭤 𐭩 𐭤𐭫𐭥𐭬).
TheCarthaginianscalled it the "Syrian Sea". In ancientSyriantexts,Phoenicianepics and in the HebrewBible, it was primarily known as the "Great Sea", הים הגדולHaYam HaGadol, (Numbers;Book of Joshua;Ezekiel) or simply as "The Sea" (1 Kings). However, it has also been called the "Hinder Sea" because of its location on the west coast of theregion of Syriaor theHoly Land(and therefore behind a person facing the east), which is sometimes translated as "Western Sea". Another name was the "Sea of thePhilistines", (Book of Exodus), from the people inhabiting a large portion of its shores near theIsraelites. InModern Hebrew, it is called הים התיכוןHaYam HaTikhon'the Middle Sea'.InClassic Persiantexts was called Daryāy-e Šām (دریای شام) "The Western Sea" or "Syrian Sea".
InModern Standard Arabic, it is known asal-Baḥr [al-Abyaḍ] al-Mutawassiṭ(البحر [الأبيض] المتوسط) 'the [White] Middle Sea'. In Islamic and older Arabic literature, it wasBaḥr al-Rūm(ī)(بحر الرومorبحر الرومي) 'the Sea of the Romans' or 'the Roman Sea'. At first, that name referred only to the eastern Mediterranean, but the term was later extended to the whole Mediterranean. Other Arabic names wereBaḥr al-šām(ī)(بحر الشام) ("the Sea of Syria") andBaḥr al-Maghrib(بحرالمغرب) ("the Sea of the West").
InTurkish, it is theAkdeniz'the White Sea'; in Ottoman,ﺁق دڭيز, which sometimes means only theAegean Sea.The origin of the name is not clear, as it is not known in earlier Greek, Byzantine or Islamic sources. It may be to contrast with theBlack Sea.In Persian, the name was translated asBaḥr-i Safīd, which was also used in laterOttoman Turkish.Similarly, in 19th century Greek, the name wasΆσπρη Θάλασσα(áspri thálassa; "white sea").
According to Johann Knobloch, inclassical antiquity, cultures in theLevantused colours to refer to the cardinal points: black referred to the north (explaining the nameBlack Sea), yellow or blue to east, red to south (e.g., theRed Sea) and white to west. That would explain theBulgarianByalo More, the TurkishAkdeniz, and the Arab nomenclature described above,lit."White Sea".
Major ancient civilisations were located around the Mediterranean. The sea provided routes for trade, colonisation, and war, as well as food (from fishing and the gathering of other seafood) for numerous communities throughout the ages.The earliest advanced civilisations in the Mediterranean were theEgyptiansand theMinoans, who traded extensively with each other. Other notable civilisations that appeared somewhat later are theHittitesand otherAnatolian peoples, thePhoenicians, andMycenean Greece. Around 1200 BC the eastern Mediterranean was greatly affected by theBronze Age Collapse, which resulted in the destruction of many cities and trade routes.
The most notable Mediterranean civilisations in classical antiquity were theGreekcity statesand thePhoenicians, both of which extensively colonised the coastlines of the Mediterranean.
Darius I of Persia, who conquered Ancient Egypt, built a canal linking theRed Seato the Nile, and thus the Mediterranean. Darius's canal was wide enough for twotriremesto pass each other with oars extended and required four days to traverse.
Following thePunic Warsin the 3rd and 2nd centuries BC, theRoman Republicdefeated theCarthaginiansto become the preeminent power in the Mediterranean. WhenAugustusfounded theRoman Empire, the Romans referred to the Mediterranean asMare Nostrum("Our Sea"). For the next 400 years, the Roman Empire completely controlled the Mediterranean Sea and virtually all its coastal regions from Gibraltar to the Levant, being the only state in history to ever do so, being given the nickname "Roman Lake".
TheWestern Roman Empirecollapsed around 476 AD. The east was again dominant as Roman power lived on in theByzantine Empireformed in the 4th century from the eastern half of theRoman Empire. Though the Eastern Roman Empire would continue to hold almost all of the Mediterranean, another power arose in the 7th century, and with it the religion ofIslam, which soon swept across from the east; at its greatest extent, the Arabs, under theUmayyads, controlled most of the Mediterranean region and left a lasting footprint on its eastern and southern shores.
A variety of foodstuffs, spices and crops were introduced to the western Mediterranean's Spain andSicilyduring Arab rule, via the commercial networks of the Islamic world. These include sugarcane,rice,cotton, alfalfa, oranges,lemons,apricots,spinach,eggplants,carrots,saffronand bananas.The Arabs also continued extensive cultivation and production of olive oil (the Spanish words for 'oil' and 'olive'—aceiteandaceituna, respectively—are derived from the Arabical-zait, meaning 'olive juice'),and pomegranates (the heraldic symbol of Granada) from classicalGreco-Romantimes.
TheArab invasionsdisrupted the trade relations between Western and Eastern Europe while disrupting trade routes with Eastern Asian Empires. This, however, had the indirect effect of promoting trade across theCaspian Sea. The export of grains fromEgyptwas re-routed towards theEastern world. Products from East Asian empires, like silk and spices, were carried from Egypt to ports likeVeniceandConstantinopleby sailors and Jewish merchants. TheViking raidsfurther disrupted the trade in western Europe and brought it to a halt. However, theNorsemendeveloped the trade from Norway to theWhite Sea, while also trading in luxury goods fromSpainand the Mediterranean. TheByzantines in the mid-8th centuryretook control of the area around the north-eastern part of the Mediterranean. Venetian ships from the 9th century armed themselves to counter the harassment by Arabs while concentrating trade of Asian goods in Venice.
TheFatimidsmaintained trade relations with theItalian city-stateslikeAmalfiandGenoabefore the Crusades, according to theCairo Genizadocuments. A document dated 996 mentions Amalfian merchants living inCairo. Another letter states that the Genoese had traded withAlexandria. The caliphal-Mustansirhad allowed Amalfian merchants to reside inJerusalemabout 1060 in place of the Latinhospice.
TheCrusadesled to the flourishing of trade between Europe and theoutremerregion.Genoa, Venice andPisacreated colonies in regions controlled by the Crusaders and came to control the trade with the Orient. These colonies also allowed them to trade with the Eastern world. Though the fall of the Crusader states and attempts at banning of trade relations with Muslim states by the Popes temporarily disrupted the trade with the Orient, it however continued.
Europe started to revive, however, as more organised and centralised states began to form in the laterMiddle Agesafter theRenaissance of the 12th century.
Ottomanpower based in Anatolia continued to grow, and in 1453 extinguished the Byzantine Empire with theConquest of Constantinople. Ottomans gained control of much of the eastern part sea in the 16th century and also maintained naval bases insouthern France(1543–1544), Algeria and Tunisia.Barbarossa, the Ottoman captain is a symbol of this domination with the victory of theBattle of Preveza(1538). TheBattle of Djerba(1560) marked the apex of Ottoman naval domination in the eastern Mediterranean. As the naval prowess of the European powers increased, they confronted Ottoman expansion in the region when theBattle of Lepanto(1571) checked the power of theOttoman Navy. This was the last naval battle to be fought primarily betweengalleys.
TheBarbary piratesofNorthwest Africapreyed on Christian shipping and coastlines in the Western Mediterranean Sea.According to Robert Davis, from the 16th to 19th centuries, pirates captured 1 million to 1.25 million Europeans as slaves.
The development of oceanic shipping began to affect the entire Mediterranean. Once, most of the trade between Western Europe and the East waspassing through the region, but after the 1490s the development of a sea route to the Indian Ocean allowed the importation of Asianspicesand other goods through the Atlantic ports of western Europe.
The sea remained strategically important. British mastery ofGibraltarensured their influence in Africa and Southwest Asia. Especially after the naval battles of Abukir (1799,Battle of the Nile) andTrafalgar(1805), the British had for a long time strengthened their dominance in the Mediterranean.Wars includedNaval warfare in the Mediterranean during World War IandMediterranean theatre of World War II.
With the opening of the locklessSuez Canalin 1869, the flow of trade between Europe and Asia changed fundamentally. The fastest route now led through the Mediterranean towards East Africa and Asia. This led to a preference for the Mediterranean countries and their ports likeTriestewith direct connections to Central and Eastern Europe experienced a rapid economic rise. In the 20th century, the 1st and 2nd World Wars as well as theSuez Crisisand theCold Warled to a shift of trade routes to the European northern ports, which changed again towards the southern ports through European integration, the activation of theSilk Roadand free world trade.
In 2013, theMaltesepresident described the Mediterranean Sea as a "cemetery" due to the large number of migrants who drowned there after their boats capsized.European ParliamentpresidentMartin Schulzsaid in 2014 that Europe's migration policy "turned the Mediterranean into a graveyard", referring to the number of drowned refugees in the region as a direct result of the policies.An Azerbaijani official described the sea as "a burial ground ... where people die".
Following the2013 Lampedusa migrant shipwreck, theItalian governmentdecided to strengthen the national system for the patrolling of the Mediterranean Sea by authorising "Operation Mare Nostrum", a military and humanitarian mission in order to rescue the migrants and arrest the traffickers of immigrants. In 2015, more than one million migrants crossed the Mediterranean Sea into Europe.
Italy was particularly affected by theEuropean migrant crisis. Since 2013, over 700,000 migrants have landed in Italy,mainly sub-Saharan Africans.
The Mediterranean Sea connects:
The 163 km (101 mi) long artificialSuez Canalin the southeast connects the Mediterranean Sea to theRed Seawithout ship lock, because the water level is essentially the same.
The westernmost point of the Mediterranean is located at the transition from theAlborán Seato the Strait of Gibraltar, the easternmost point is on the coast of theGulf of Iskenderunin southeastern Turkey. The northernmost point of the Mediterranean is on the coast of theGulf of TriestenearMonfalconein northern Italy while the southernmost point is on the coast of theGulf of Sidranear the Libyan town ofEl Agheila.
Large islands in the Mediterranean include:
TheAlpine arc, which also has a great meteorological impact on the Mediterranean area, touches the Mediterranean in the west in the area aroundNice.
The typicalMediterranean climatehas hot, dry summers and mild, rainy winters. Crops of the region includeolives,grapes,oranges,tangerines,carobsandcork.
The Mediterranean Sea includes 15marginal seas:
Note 1: TheInternational Hydrographic Organizationdefines the area as generic Mediterranean Sea, in the Western Basin. It does not recognize the labelSea of Sardinia.
Note 2:Thracian SeaandMyrtoan Seaareseasthat are part of theAegean Sea.
Note 3: TheBlack Seais not considered part of it.
TheInternational Hydrographic Organizationdefines the limits of the Mediterranean Sea as follows:Stretching from theStrait of Gibraltarin the west to the entrances to theDardanellesand theSuez Canalin the east, the Mediterranean Sea is bounded by the coasts of Europe, Africa, and Asia and is divided into two deep basins:
Thedrainage basinof the Mediterranean Sea is particularly heterogeneous and extends much further than the Mediterranean region.Its size has been estimated between 4,000,000 and 5,500,000 km(1,500,000 and 2,100,000 sq mi),depending on whether non-active parts (deserts) are included or not.The longest river ending in the Mediterranean Sea is theNile, which takes its sources in equatorial Africa. The basin of the Nile constitutes about two-thirds of the Mediterranean drainage basinand encompasses areas as high as theRuwenzori Mountains.Among other important rivers in Africa, are theMoulouyaand theChelif, both on the north side of theAtlas Mountains. In Asia, are theCeyhanandSeyhan, both on the south side of theTaurus Mountains.In Europe, the largest basins are those of theRhône,Ebro,Po, andMaritsa.The basin of the Rhône is the largest and extends up as far north as theJura Mountains, encompassing areas even on the north side of theAlps.The basins of the Ebro, Po, and Maritsa, are respectively south of thePyrenees, Alps, andBalkan Mountains, which are the major ranges bordering Southern Europe.
Total annual precipitation is significantly higher on the European part of the Mediterranean basin, especially near the Alps (the 'water tower of Europe') and other high mountain ranges. As a consequence, theriver dischargesof the Rhône and Po are similar to that of the Nile, despite the latter having a much larger basin.These are the only three rivers with an average discharge of over 1,000 m/s (35,000 cu ft/s).Among large natural fresh bodies of water areLake Victoria(Nile basin),Lake Geneva(Rhône), and theItalian Lakes(Po). While the Mediterranean watershed is bordered by other river basins in Europe, it is essentially bordered byendorheic basinsor deserts elsewhere.
The following countries are in the Mediterranean drainage basin whilenothaving a coastline on the Mediterranean Sea:
The following countries have a coastline on the Mediterranean Sea:
Several other territories also border the Mediterranean Sea (from west to east):
Exclusive economic zonesin Mediterranean Sea:
TheCoastline lengthis about 46,000 km (29,000 mi).
Major cities (municipalities), with populations larger than 200,000 people, bordering the Mediterranean Sea include:
TheInternational Hydrographic Organization(IHO) divides the Mediterranean into a number of smaller waterbodies, each with their own designation (from west to east):
Some other seas whose names have been in common use from the ancient times, or in the present:
Many of these smaller seas feature in local myth and folklore and derive their names from such associations.
In addition to the seas, a number of gulfs andstraitsare recognised:
The Mediterranean Sea encompasses about 10,000 islands and islets, of which about 250 are permanently inhabited.In the table below are listed the ten largest by size.
Much of the Mediterranean coast enjoys ahot-summer Mediterranean climate. However, most of its southeastern coast has ahot desert climate, and much of Spain's eastern (Mediterranean) coast has acold semi-arid climate, while most of Italy's northern (Adriatic) coast has ahumid subtropical climate. Although they are rare,tropical cyclones occasionally form in the Mediterranean Sea, typically in September–November.
The Mediterranean Sea has numerousunderwatergeologicalfeatures formed by thesubductionof theAfrican Platebeneath theEurasian Plate.The sea is divided naturally into western andeasternregions by theMalta Escarpment that runs from the island ofSicilyto theAfricancoast.
Thewestern Mediterranean regionmay be separated into three main underwater basins:
Theeastern Mediterraneanregion may also be subdivided into the following underwater basins:
Until the 1960s, the Mediterranean was believed to be the primary remaining portion of the earlier (200 million years old)MesozoicTethys Ocean, which once encircled theEastern Hemisphere. However, since the late 20th century, research using the theory of seafloor spreading has indicated that most of the current Mediterranean seafloor is not a portion of the Tethys sea floor.Some researchers consider the Ionian Basin, to the east of the Malta Escarpment, to be the remnant of the Tethys Ocean.Over the course of the last 44 million years, the continental plates of Africa andEurasiahave converged and receded, resulting in the current tectonically active basin and its surrounding mountain chains. According to the interpretation of geologic data, there are currently several major places where Africa and Eurasia collide, causing land submergence, mountain building, and volcanism.
Sediment coresdrilled in 1970 and 1975 led to theories that about 6 million years ago, the Mediterranean was around 3,000 metres (10,000 ft) below the current sea level and included arid deserts blanketed with evaporite salts. It was thought that Gibraltar's high ridges prevented Atlantic waters from entering until roughly 5.5 million years ago, when they broke through and flooded the Mediterranean. According to more recent seismic and microfossil research, the seafloor was never entirely dry. Rather approximately 5 million years ago, the seafloor was made up of many basins with varying topography and sizes, spanning in depth from 200 to 1,520 metres (650 to 5,000 ft). Salts were likely accumulated on the bottom of highly salinised waters of widely differing depths. The uncertainty of the timing and nature of sea-bottom salt formation and evidence from later seismic research andcore sampleshas been the subject of intense scientific debate.
TheMalta Escarpmentis a 250-kilometre (160 mi)undersealimestoneescarpmentthat stretches south from Sicily's eastern coast to theMaltese islands' eastern coast and beyond, primarily formed due to tectonic activities.There are more than 500 undersea canyons along the cliffs, which can reach heights of 3.5 kilometres (2.2 mi) in some locations. Rich biological communities may be found in the canyons, which also serve as channels for contaminants and nutrients due to underwater currents. These deep valleys are special due to the fact that they were not carved out by surface rivers. Underwaterlandslidesare among the natural hazards found on the Malta Escarpment. TheUniversity of Malta,UK National Oceanography Centre,New Zealand National Institute of Water and Atmospheric Research,University College DublinandItaly’s Istituto Nazionale di Oceanografia e Geofisicacollaborated on a recent study financed by theEuropean Unionthat focused on the Escarpment.
Being nearly landlocked affects conditions in the Mediterranean Sea: for instance,tidesare very limited as a result of the narrow connection with the Atlantic Ocean. The Mediterranean is characterised and immediately recognised by its deep blue colour.
Evaporationgreatly exceedsprecipitationand river runoff in the Mediterranean, a fact that is central to the water circulation within the basin.Evaporation is especially high in its eastern half, causing the water level to decrease andsalinityto increase eastward.The average salinity in the basin is 38PSUat 5 m (16 ft) depth.The temperature of the water in the deepest part of the Mediterranean Sea is 13.2 °C (55.8 °F).
The net water influx from the Atlantic Ocean is ca. 70,000 m/s (2.5 million cu ft/s) or 2.2×10m/a (7.8×10cu ft/a).Without this Atlantic water, the sea level of the Mediterranean Sea would fall at a rate of about 1 m (3 ft) per year.
Inoceanography, it is sometimes called theEurafrican Mediterranean Sea, theEuropean Mediterranean Seaor theAfrican Mediterranean Seato distinguish it frommediterranean seaselsewhere.
Water circulationin the Mediterranean can be attributed to the surface waters entering from theAtlanticthrough theStrait of Gibraltar(and also low salinity water entering the Mediterranean from the Black Sea through the Bosphorus). The cool and relatively low-salinity Atlantic water circulates eastwards along the North African coasts. A part of the surface water does not pass the Strait of Sicily, but deviates towardsCorsicabefore exiting the Mediterranean. The surface waters entering the eastern Mediterranean Basin circulate along the Libyan and Israeli coasts. Upon reaching theLevantine Sea, the surface waters having warmed and increased its salinity from its initial Atlantic state, is now denser and sinks to form the Levantine Intermediate Waters (LIW). Most of the water found anywhere between 50 and 600 m (160 and 2,000 ft) deep in the Mediterranean originates from the LIW.LIW are formed along the coasts of Turkey and circulate westwards along the Greek and south Italian coasts. LIW are the only waters passing the Sicily Strait westwards. After the Strait of Sicily, the LIW waters circulate along the Italian, French and Spanish coasts before exiting the Mediterranean through the depths of the Strait of Gibraltar. Deep water in the Mediterranean originates from three main areas: theAdriatic Sea, from which most of the deep water in the eastern Mediterranean originates, theAegean Sea, and theGulf of Lion. Deep water formation in the Mediterranean is triggered by strong winterconvectionfueled by intense cold winds like theBora. When new deep water is formed, the older waters mix with the overlaying intermediate waters and eventually exit the Mediterranean. Theresidence time of waterin the Mediterranean is approximately 100 years, making the Mediterranean especially sensitive to climate change.
Being a semi-enclosed basin, the Mediterranean experiences transitory events that can affect the water circulation on short time scales. In the mid-1990s, the Aegean Sea became the main area for deep water formation in the eastern Mediterranean after particularly cold winter conditions. This transitory switch in the origin of deep waters in the eastern Mediterranean was termed Eastern Mediterranean Transient (EMT) and had major consequences on water circulation of the Mediterranean.
Another example of a transient event affecting the Mediterranean circulation is the periodic inversion of the North Ionian Gyre, which is ananticyclonicocean gyreobserved in the northern part of theIonian Sea, off the Greek coast. The transition from anticyclonic to cyclonic rotation of this gyre changes the origin of the waters fueling it; when the circulation is anticyclonic (most common), the waters of the gyre originate from the Adriatic Sea. When the circulation is cyclonic, the waters originate from theLevantine Sea. These waters have different physical and chemical characteristics, and the periodic inversion of the North Ionian Gyre (called Bimodal Oscillating System or BiOS) changes the Mediterranean circulation and biogeochemistry around the Adriatic and Levantine regions.
Because of the short residence time of its waters, the Mediterranean Sea is considered a hot-spot for climate change records,registering indeed marked increases in temperature across the entire water column since the 1950s.According to climate projections, the decrease in precipitation over the region will lead to more
evaporation, ultimately increasing marine salinity.As a result of both temperature and salinity increases, the Mediterranean Sea is likely to become more stratified by the end of the 21st century, with notable consequences on water circulation andbiogeochemistry. The stratification and warming have already led the eastern Mediterranean to become a net source of CO2to the atmospherenotably during summer.
Human-induced climate change appears to play a growing role in the development ofmarine heatwavesthat have become a prominent subject of research in recent years, particularly in the Mediterranean where a number of areas in both western and eastern sub-basins now experience peaks of temperatures, along with more frequent, more intense, more prolonged warming events than ever seen on record. These events, mainly driven by a combination of oceanic and atmospheric factors, are often triggered by high pressure systems that will reduce cloud cover and increase solar absorption by the sea surface.  Their impacts on marine ecosystems, such as mass mortality in benthic communities, coral bleaching events, disruptions in fishery catches and shifts in species distributions, can be devastating.Extreme warming can lead tobiodiversity lossand presents an existential threat to some habitatswhile making conditions more hospitable to invasive tropical species.
In spite of its greatbiodiversity, concentrations ofchlorophylland nutrients in the Mediterranean Sea are very low, making it one of the mostoligotrophicocean regions in the world. The Mediterranean Sea is commonly referred to as anLNLC (Low-Nutrient, Low-Chlorophyll) area. The Mediterranean Sea fits the definition of adesertin which its nutrient contents are low, making it difficult for plants and animals to develop.
There are steep gradients in nutrient concentrations, chlorophyll concentrations and primary productivity in the Mediterranean. Nutrient concentrations in the western part of the basin are about double the concentrations in the eastern basin. TheAlboran Sea, close to theStrait of Gibraltar, has a dailyprimary productivityof about 0.25 g C (grams of carbon) mdaywhereas the eastern basin has an average daily productivity of 0.16 g C mday.For this reason, the eastern part of the Mediterranean Sea is termed "ultraoligotrophic". The productive areas of the Mediterranean Sea are few and small. High (i.e. more than 0.5 grams ofChlorophyllaper cubic meter) productivity occurs in coastal areas, close to the river mouths which are the primary suppliers of dissolved nutrients. TheGulf of Lionhas a relatively high productivity because it is an area of high vertical mixing, bringing nutrients to the surface waters that can be used byphytoplanktonto produce Chlorophylla.
Primary productivity in the Mediterranean is also marked by an intense seasonal variability. In winter, the strong winds and precipitation over the basin generatevertical mixing, bringing nutrients from the deep waters to the surface, where phytoplankton can convert it intobiomass.However, in winter, light may be the limiting factor for primary productivity. Between March and April, spring offers the ideal trade-off between light intensity and nutrient concentrations in surface for aspring bloomto occur. In summer, high atmospheric temperatures lead to the warming of the surface waters. The resultingdensitydifference virtually isolates the surface waters from the rest of the water column and nutrient exchanges are limited. As a consequence, primary productivity is very low between June and October.
Oceanographic expeditions uncovered a characteristic feature of the Mediterranean Sea biogeochemistry: most of the chlorophyll production does not occur on the surface, but in sub-surface waters between 80 and 200 meters deep.Another key characteristic of the Mediterranean is its high nitrogen-to-phosphorus ratio (N:P).Redfielddemonstrated that most of the world's oceans have an average N:P ratio around 16. However, the Mediterranean Sea has an average N:P between 24 and 29, which translates a widespread phosphorus limitation.
Because of its low productivity, plankton assemblages in the Mediterranean Sea are dominated by small organisms such aspicophytoplanktonandbacteria.
Thegeologic historyof the Mediterranean Sea is complex. Underlain byoceanic crust, the sea basin was once thought to be a tectonic remnant of the ancientTethys Ocean; it is now known to be a structurally younger basin, called theNeotethys, which was first formed by the convergence of theAfrican PlateandEurasian Plateduring the LateTriassicand EarlyJurassic. Because it is a near-landlocked body of water in a normally dry climate, the Mediterranean is subject to intensive evaporation and the precipitation ofevaporites. TheMessinian salinity crisisstarted about six million years ago (mya) when the Mediterranean became landlocked, and then essentially dried up. There are salt deposits accumulated on the bottom of the basin of more than a million cubic kilometres—in some places more than three kilometres thick.
Scientists estimate that the sea was last filled about 5.3 million years ago (mya) in less than two years by theZanclean flood. Water poured in from the Atlantic Ocean through a newly breached gateway now called theStrait of Gibraltarat an estimated rate of about three orders of magnitude (one thousand times) larger than the current flow of theAmazon River.
The Mediterranean Sea has an average depth of 1,500 m (4,900 ft) and the deepest recorded point is 5,267 m (17,280 ft) in theCalypso Deepin theIonian Sea. The coastline extends for 46,000 km (29,000 mi). A shallow submarine ridge (theStrait of Sicily) between the island ofSicilyand the coast ofTunisiadivides the sea in two main subregions: the Western Mediterranean, with an area of about 850,000 km(330,000 sq mi); and the Eastern Mediterranean, of about 1.65 million km(640,000 sq mi). Coastal areas have submarinekarst springsorvruljas, which discharge pressurised groundwater into the water from below the surface; the discharge water is usually fresh, and sometimes may be thermal.
The Mediterranean basin and sea system were established by the ancient African-Arabian continent colliding with theEurasiancontinent. As Africa-Arabia drifted northward, it closed over the ancientTethys Oceanwhich had earlier separated the two supercontinentsLaurasiaandGondwana.
At about that time in the middleJurassicperiod (roughly 170 million years ago) a much smaller sea basin, dubbed theNeotethys, was formed shortly before the Tethys Ocean closed at its western (Arabian) end. The broad line of collisions pushed up a very long system of mountains from thePyreneesin Spain to theZagros Mountainsin Iran in an episode of mountain-building tectonics known as theAlpine orogeny. The Neotethys grew larger during the episodes of collisions (and associated foldings and subductions) that occurred during theOligoceneandMioceneepochs (34 to 5.33 mya); see animation:Africa-Arabia colliding with Eurasia. Accordingly, the Mediterraneanbasinconsists of several stretchedtectonicplates insubductionwhich are the foundation of the eastern part of the Mediterranean Sea. Various zones of subduction contain the highest oceanic ridges, east of theIonian Seaand south of theAegean. TheCentral Indian Ridgeruns east of the Mediterranean Sea south-east across the in-betweenofAfricaand theArabian Peninsulainto theIndian Ocean.
DuringMesozoicandCenozoictimes, as the northwest corner of Africa converged on Iberia, it lifted the Betic-Rifmountain beltsacross southern Iberia and northwest Africa. There the development of the intramontane Betic and Rif basins created two roughly parallel marine gateways between the Atlantic Ocean and the Mediterranean Sea. Dubbed theBeticandRifian corridors, they gradually closed during the middle and late Miocene: perhaps several times.In the late Miocene the closure of theBetic Corridortriggered the so-called "Messinian salinity crisis" (MSC), characterised by the deposition of a thick evaporitic sequence – with salt deposits up to 2 km thick in the Levantine sea – and by a massive drop in water level in much of the Basin. This event was for long the subject of acute scientific controversy, now much appeased,regarding its sequence, geographic range, processes leading to evaporite facies and salt deposits. The start of the MSC was recently estimated astronomically at 5.96 mya, and it persisted for some 630,000 years until about 5.3 mya;see Animation: Messinian salinity crisis, at right.
After the initial drawdownand re-flooding, there followed more episodes—the total number is debated—of sea drawdowns and re-floodings for the duration of the MSC. It ended when the Atlantic Ocean last re-flooded the basin—creating theStrait of Gibraltarand causing theZanclean flood—at the end of the Miocene (5.33 mya). Some research has suggested that a desiccation-flooding-desiccation cycle may have repeated several times, which could explain several events of large amounts of salt deposition.Recent studies, however, show that repeated desiccation and re-flooding is unlikely from ageodynamicpoint of view.
The present-day Atlantic gateway, theStrait of Gibraltar, originated in the early Pliocene via theZanclean Flood. As mentioned, there were two earlier gateways: theBetic Corridoracross southern Spain and the Rifian Corridor across northern Morocco. The Betic closed about 6 mya, causing the Messinian salinity crisis (MSC); the Rifian or possibly both gateways closed during the earlierTortoniantimes, causing a "Tortonian salinity crisis" (from 11.6 to 7.2 mya), long before the MSC and lasting much longer. Both "crises" resulted in broad connections between the mainlands of Africa and Europe, which allowed migrations of flora and fauna—especially large mammals including primates—between the two continents. TheVallesian crisisindicates a typical extinction and replacement of mammal species in Europe during Tortonian times following climatic upheaval and overland migrations of new species:see Animation: Messinian salinity crisis (and mammal migrations), at right.
The almost complete enclosure of the Mediterranean basin has enabled the oceanic gateways to dominate seawater circulation and the environmental evolution of the sea and basin. Circulation patterns are also affected by several other factors—including climate, bathymetry, and water chemistry and temperature—which are interactive and can induce precipitation ofevaporites. Deposits of evaporites accumulated earlier in the nearbyCarpathian foredeepduring theMiddle Miocene, and the adjacentRed Sea Basin(during theLate Miocene), and in the whole Mediterranean basin (during the MSC and theMessinianage). Manydiatomitesare found underneath the evaporite deposits, suggesting a connection between theirformations.
Today, evaporation of surface seawater (output) is more than the supply (input) of fresh water by precipitation and coastal drainage systems, causing the salinity of the Mediterranean to be much higher than that of the Atlantic—so much so that the saltier Mediterranean waters sink below the waters incoming from the Atlantic, causing a two-layer flow across the Strait of Gibraltar: that is, an outflowsubmarine currentof warm saline Mediterranean water, counterbalanced by an inflow surface current of less saline cold oceanic water from the Atlantic. In the 1920s, Herman Sörgel proposed the building of a hydroelectric dam (theAtlantropaproject) across the Straits, using the inflow current to provide a large amount of hydroelectric energy. The underlying energy grid was also intended to support a political union between Europe and, at least, the Maghreb part of Africa (compareEurafrikafor the later impact andDesertecfor a later project with some parallels in the planned grid).
The end of theMiocenealso marked a change in the climate of the Mediterranean basin. Fossil evidence from that period reveals that the larger basin had a humid subtropical climate with rainfall in the summer supportinglaurel forests. The shift to a "Mediterranean climate" occurred largely within the last three million years (the latePlioceneepoch) as summer rainfall decreased. The subtropical laurel forests retreated; and even as they persisted on the islands ofMacaronesiaoff the Atlantic coast of Iberia and North Africa, the present Mediterranean vegetation evolved, dominated by coniferous trees andsclerophylloustrees and shrubs with small, hard, waxy leaves that prevent moisture loss in the dry summers. Much of these forests and shrublands have been altered beyond recognition by thousands of years of human habitation. There are now very few relatively intact natural areas in what was once a heavily wooded region.
Because of its latitude and its landlocked position, the Mediterranean is especially sensitive to astronomically induced climatic variations, which are well documented in its sedimentary record. Since the Mediterranean is subject to the deposition ofeolian dustfrom theSaharaduring dry periods, whereas riverinedetritalinput prevails during wet ones, the Mediterranean marinesapropel-bearing sequences provide high-resolution climatic information. These data have been employed in reconstructing astronomically calibrated time scales for the last 9 Ma of the Earth's history, helping to constrain the time of pastgeomagnetic reversals.Furthermore, the exceptional accuracy of these paleoclimatic records has improved our knowledge of the Earth's orbital variations in the past.
Unlike the vast multidirectionalocean currentsin openoceanswithin their respectiveoceanic zones;biodiversityin the Mediterranean Sea is stable due to the subtle but strong locked nature ofcurrentswhich is favourable to life, even the smallest macroscopic type ofvolcanic life form. The stablemarine ecosystemof the Mediterranean Sea andsea temperatureprovides a nourishing environment forlife in the deep seato flourish while assuring a balancedaquatic ecosystemexcluded from any externaldeepoceanic factors. It is estimated that there are more than 17,000marine speciesin the Mediterranean Sea with generally higher marinebiodiversityincoastal areas,continental shelves, and decreases with depth.
As a result of the drying of the sea during theMessinian salinity crisis,the marine biota of the Mediterranean is derived primarily from the Atlantic Ocean. The North Atlantic is considerably colder and more nutrient-rich than the Mediterranean, and the marine life of the Mediterranean has had to adapt to its differing conditions in the five million years since the basin was reflooded.
TheAlboran Seais a transition zone between the two seas, containing a mix of Mediterranean and Atlantic species. The Alboran Sea has the largest population ofbottlenose dolphinsin the Western Mediterranean, is home to the last population ofharbour porpoisesin the Mediterranean and is the most important feeding grounds forloggerhead sea turtlesin Europe. The Alboran Sea also hosts important commercial fisheries, includingsardinesandswordfish. TheMediterranean monk sealslive in the Aegean Sea in Greece. In 2003, theWorld Wildlife Fundraised concerns about the widespreaddrift netfishing endangering populations of dolphins, turtles, and other marine animals such as thespiny squat lobster.
There was a resident population oforcasin the Mediterranean until the 1980s, when they went extinct, probably due to long-term PCB exposure. There are still annual sightings of orca vagrants.
For 4,000 years, human activity has transformed most parts of Mediterranean Europe, and the "humanisation of the landscape" overlapped with the appearance of the present Mediterranean climate.The image of a simplistic, environmental determinist notion of a Mediterranean paradise on Earth in antiquity, which was destroyed by later civilisations, dates back to at least the 18th century and was for centuries fashionable in archaeological and historical circles. Based on a broad variety of methods, e.g. historical documents, analysis of trade relations,floodplainsediments,pollen, tree-ring and further archaeometric analyses and population studies,Alfred Thomas Grove's andOliver Rackham's work on "The Nature of Mediterranean Europe" challenges this common wisdom of a Mediterranean Europe as a "Lost Eden", a formerly fertile and forested region, that had been progressively degraded and desertified by human mismanagement.The belief stems more from the failure of the recent landscape to measure up to the imaginary past of theclassicsas idealised by artists, poets and scientists of the early modernEnlightenment.
The historical evolution of climate, vegetation and landscape in southern Europe from prehistoric times to the present is much more complex and underwent various changes. For example, some of the deforestation had already taken place before the Roman age. While in the Roman age large enterprises such as thelatifundiatook effective care of forests and agriculture, the largest depopulation effects came with the end of the empire. Someassume that the major deforestation took place in modern times—the later usage patterns were also quite different e.g. in southern and northern Italy. Also, the climate has usually been unstable and there is evidence of various ancient and modern "Little Ice Ages",and plant cover accommodated to various extremes and became resilient to various patterns of human activity.
Even Grove considered that human activity could be the cause of climate change. Modern science has been able to provide clear evidence of this. The wide ecological diversity typical of Mediterranean Europe is predominantly based on human behaviour, as it is and has been closely related to human usage patterns.The diversity rangewas enhanced by the widespread exchange and interaction of the longstanding and highly diverse local agriculture, intense transport and trade relations, and the interaction with settlements, pasture and other land use. The greatest human-induced changes, however, came afterWorld War II, in line with the "1950s syndrome"as rural populations throughout the region abandoned traditional subsistence economies. Grove and Rackham suggest that the locals left the traditional agricultural patterns and instead became scenery-setting agentsfor tourism. This resulted in more uniform, large-scale formations.Among further current important threats to Mediterranean landscapes are overdevelopment of coastal areas, abandonment of mountains and, as mentioned, the loss of variety via the reduction of traditional agricultural occupations.
The Mediterranean region is one of the most geologically active maritime area of the globe, sitting on a complex tectonic boundary zone between the European and African plates. The geology of the region, with the presence of plate boundaries and active faults, makes it prone to quite frequent earthquakes, tsunamis and submarine landslides with can have devastating consequences in densely populated coastal areas. In addition climate change now intensifies the frequency and impacts of storm surges and coastal flooding, putting additional human lives and property at risk.
Earthquakesare relatively frequent in the Mediterranean Basin, ranking among the most damaging geohazards. One of the most destructive was the Crete earthquake in 365 BC, with Mw > 8, which lifted the western tip of the island by up to 9 m and caused a mega tsunami that destroyed many harbors in the eastern sub-basin.
Volcanic eruptionsare not uncommon either and left their mark in historical and archaeological records. The largest include theThera eruption, dated around 1600 BC, and the eruptions ofMount Vesuviusin 217 BC and AD 79 - the latter famously known for the destruction and the burying of the ancient cities ofPompeiiandHerculaneum.In the same region thePhlegraean Fieldswest of Naples constitute one of the most significant volcanic systems in the world, still very active. In the same general area, volcanoes like Mt. Etna and Stromboli are considered in a state of permanent activity, with frequent eruptions and lava emissions through the past 1500 years.
Tsunamis, usually triggered by earthquakes, volcanic eruptions and submarine landslides, have caused a number of documented disasters in the Mediterranean Basin in the past 2500 years. Historical examples include the 365 and 1303 tsunamis in the Hellenic Arc, more recently the disastrous 1908 event that destroyed the cities of Messina and Reggio Calabria, and the large tsunami that occurred off the Algerian margin in 2003.
On the diplomatic front, the experience of coastal countries and regional authorities is leadding to exchangeat the international level with the cooperation of NGOs, states, regional and municipal authorities.TheGreek–Turkish earthquake diplomacyis a quite positive example of natural hazards leading to improved relations between traditional rivals in the region after earthquakes in İzmit and Athens in 1999. The European Union Solidarity Fund (EUSF) was set up to respond to major natural disasters and express European solidarity to disaster-stricken regions within all of Europe.The largest amount of funding requests in the EU relates toforest fires, followed by floods and earthquakes. Forest fires, whether human-made or natural, are a frequent and dangerous hazard in the Mediterranean region.Tsunamisare also an often-underestimated hazard in the region. For example, the1908 Messina earthquakeand tsunami took more than 123,000 lives in Sicily and Calabria and were among the deadliest natural disasters in modern Europe.
The opening of theSuez Canalin 1869 created the first salt-water passage between the Mediterranean and theRed Sea. The Red Sea is higher than theEastern Mediterranean, so the canal functions as atidal straitthat pours Red Sea water into the Mediterranean. TheBitter Lakes, which are hyper-saline natural lakes that form part of the canal, blocked the migration of Red Sea species into the Mediterranean for many decades, but as the salinity of the lakes gradually equalised with that of the Red Sea, the barrier to migration was removed, and plants and animals from the Red Sea have begun to colonise the Eastern Mediterranean. The Red Sea is generally saltier and more nutrient-poor than the Atlantic, so the Red Sea species have advantages over Atlantic species in the salty and nutrient-poor Eastern Mediterranean. Accordingly, Red Sea species invade the Mediterranean biota, and not vice versa; this phenomenon is known as theLessepsian migration(afterFerdinand de Lesseps, the French engineer) or Erythrean ("red") invasion. The construction of theAswan High Damacross theNileRiver in the 1960s reduced the inflow of freshwater and nutrient-richsiltfrom the Nile into the Eastern Mediterranean, making conditions there even more like the Red Sea and worsening the impact of theinvasive species.
Invasive species have become a major component of the Mediterranean ecosystem and have serious impacts on the Mediterranean ecology, endangering a number of local andendemicMediterranean species. A first look at some groups of marine species shows that over 70% of exoticdecapodsand some 2/3 of exotic fishesfound in the Mediterranean are ofIndo-Pacificorigin,introducedfrom the Red Sea via the Suez Canal. This makes the Canal the first pathway of arrival ofalienspecies into the Mediterranean. The impacts of some Lessepsian species have proven to be considerable, mainly in the Levantine basin of the Mediterranean, where they are replacing native species and becoming a familiar sight.
According to definitions by theMediterranean Science Commissionand theInternational Union for Conservation of Nature, and toConvention on Biological Diversity(CBD) andRamsar Conventionterminologies, they are alien species, as they are non-native (non-indigenous) to the Mediterranean Sea, and are found outside their normal, non-adjacent area of distribution. When these species succeed in establishing populations in the Mediterranean Sea, compete with and begin to replace native species they are "Alien Invasive Species", as they are an agent of change and a threat to the native biodiversity. In the context of CBD, "introduction" refers to the movement by human agency, indirect or direct, of an alien species outside of its natural range (past or present). The Suez Canal, being an artificial (human-made) canal, is a human agency. Lessepsian migrants are therefore "introduced" species (indirect, and unintentional). Whatever wording is chosen, they represent a threat to the native Mediterranean biodiversity, because they are non-indigenous to this sea. In recent years, the Egyptian government's announcement of its intentions to deepen and widen the Canalraised concerns frommarine biologists, fearing that such an act will only worsen the invasion of Red Sea species into the Mediterranean, and lead to even more species passing through the Canal.
In recent decades, the arrival of exotic species from the tropical Atlantic has become noticeable. In many cases this reflects an expansion – favoured by a warming trend of sub-tropical Atlantic waters, and also by a fast-growing maritime traffic – of the natural range of species that now enter the Mediterranean through theStrait of Gibraltar. While not as intense asLessepsian migration, the process is of importance and is therefore receiving increased levels of scientific coverage.
By 2100 the overall level of the Mediterranean could rise between 3 and 61 cm (1.2 and 24.0 in) as a result of theeffects of climate change.This could have adverse effects on populations across the Mediterranean:
Coastal ecosystems also appear to be threatened bysea level rise, especially enclosed seas such as theBaltic, the Mediterranean and the Black Sea. These seas have only small and primarily east–west movementcorridors, which may restrict northward displacement of organisms in these areas.Sea level rise for the next century (2100) could be between 30 and 100 cm (12 and 39 in) and temperature shifts of a mere 0.05–0.1 °C (0.09–0.18 °F) in the deep sea are sufficient to induce significant changes in species richness and functional diversity.
Pollutionin this region has been extremely high in recent years.TheUnited Nations Environment Programmehas estimated that 650,000,000 t (720,000,000 short tons) ofsewage, 129,000 t (142,000 short tons) ofmineral oil, 60,000 t (66,000 short tons) of mercury, 3,800 t (4,200 short tons) of lead and 36,000 t (40,000 short tons) ofphosphatesare dumped into the Mediterranean each year.TheBarcelona Conventionaims to 'reduce pollution in the Mediterranean Sea and protect and improve the marine environment in the area, thereby contributing to its sustainable development.'Many marine species have been almost wiped out because of the sea's pollution. One of them is theMediterranean monk sealwhich is considered to be among the world's mostendangeredmarine mammals.The Mediterranean is also plagued bymarine debris. A 1994 study of theseabedusingtrawl netsaround the coasts of Spain, France and Italy reported a particularly high mean concentration of debris; an average of 1,935 items per km(5,010/sq mi).
Some of the world's busiest shipping routes are in the Mediterranean Sea. In particular, the Maritime Silk Road from Asia and Africa leads through the Suez Canal directly into the Mediterranean Sea to its deep-water ports inValencia,Piraeus,Trieste,Genoa,MarseilleandBarcelona. It is estimated that approximately 220,000merchant vesselsof more than 100tonnescross the Mediterranean Sea each year—about one-third of the world's total merchant shipping. These ships often carry hazardous cargo, which if lost would result in severe damage to the marine environment.
The discharge of chemical tank washings and oily wastes also represent a significant source of marine pollution. The Mediterranean Sea constitutes 0.7% of the global water surface and yet receives 17% of global marine oil pollution. It is estimated that every year between 100,000 and 150,000 t (98,000 and 148,000 long tons) of crude oil are deliberately released into the sea from shipping activities.
Approximately 370,000,000 t (360,000,000 long tons) of oil are transported annually in the Mediterranean Sea (more than 20% of the world total), with around 250–300oil tankerscrossing the sea every day. An important destination is thePort of Trieste, the starting point of theTransalpine Pipeline, which covers 40% of Germany's oil demand (100% of the federal states of Bavaria and Baden-Württemberg), 90% of Austria and 50% of the Czech Republic.Accidentaloil spillshappen frequently with an average of 10 spills per year. A major oil spill could occur at any time in any part of the Mediterranean.
The coast of the Mediterranean has been used for tourism since ancient times, as the Roman villa buildings on theAmalfi Coastor inBarcolashow. From the end of the 19th century, in particular, the beaches became places of longing for many Europeans and travellers. From then on, and especially after World War II,mass tourismto the Mediterranean began with all its advantages and disadvantages. While initially, the journey was by train and later by bus or car, today the plane is increasingly used.
Tourism is today one of the most important sources of income for many Mediterranean countries, despite the human-made geopolitical conflictsin the region. The countries have tried to extinguish rising human-made chaotic zonesthat might affect the region's economies and societies in neighbouring coastal countries, andshipping routes. Naval and rescue components in the Mediterranean Sea are considered to be among the bestdue to the rapid cooperation between variousnaval fleets. Unlike the vast open oceans, the sea's closed position facilitates effective naval and rescue missions, considered the safestand regardless ofany human-made ornatural disaster.
Tourism is a source of income for small coastal communities, including islands, independent of urban centres. However, tourism has also played a major role in thedegradationof the coastal andmarine environment. Rapid development has been encouraged by Mediterranean governments to support the large numbers of tourists visiting the region, but this has caused serious disturbance tomarine habitatsby erosion andpollutionin many places along the Mediterranean coasts.
Tourism often concentrates in areas of high natural wealth, causing a serious threat to the habitats of endangered species such assea turtlesandmonk seals. Reductions in natural wealth may reduce the incentive for tourists to visit.
Fish stock levels in the Mediterranean Sea are alarmingly low. The European Environment Agency says that more than 65% of all fish stocks in the region are outside safe biological limits and the United Nations Food and Agriculture Organisation, that some of the most important fisheries—such asalbacoreandbluefin tuna,hake,marlin,swordfish,red mulletandsea bream—are threatened.
There are clear indications that catch size and quality have declined, often dramatically, and in many areas, larger and longer-lived species have disappeared entirely from commercial catches.
Large open-water fish like tuna have been a shared fisheries resource for thousands of years but the stocks are now dangerously low. In 1999,Greenpeacepublished a report revealing that the amount of bluefin tuna in the Mediterranean had decreased by over 80% in the previous 20 years and government scientists warn that without immediate action the stock will collapse.
A study showed thatclimate change-relatedexceptionalmarine heatwavesin the Mediterranean Sea during 2015–2019 resulted in widespread mass sealife die-offs in five consecutive years.