Mediterranean: Between Reality and Utopia Photographers' Gallery London WC2 until 3 October
Classical geographers thought of the Mediterranean as the Earth's centre. For them it was the buoyant source of life, and also the wine-dark, nurturing basis of culture. Its position on their maps of a small, autonomous world made it uterine; the same sea nowadays - befouled, congested, embattled, criss-crossed by a flotilla of drug-smugglers and people-traffickers - is Earth's lax sphincter.
Deities once dwelt in it, and Aphrodite was born from its spermatic foam. Contemporary trippers, who use the sea as an alibi for a fortnight of binges and orgies on Majorca or Rhodes, are more likely to limp home with a sterilising dose of chlamydia.
The Photographer's Gallery, in its group exhibition Mediterranean: Between Reality and Utopia, makes photography itself take some of the blame for the Mediterranean's lapse from grace. The sea is a victim of its popularity and publicity; it has been photographed to death, as Christophe Bourguedieu suggests by rephotographing a rack of tacky postcards from Tangier. Innumerable amateurish snappers have reduced it to a fuzzy background, a view that the camera looks at for them.
Somehow all those happy holidaymakers who have adopted stiff, self-conscious poses on the coast seem to linger invisibly, using up the air and dirtying the water. Eric Kessels prides himself on having discovered, in a Barcelona market, a suitcase of anonymous holiday snaps that show the same woman preening on a succession of Mediterranean beaches every summer from 1956 to 1969. His find sadly implies a death, or at least the end of an affair. But I'm not sure that this elegiac motive makes the photographs worth exhibiting. No one else can see that ordinary woman with the enraptured gaze of her lover, and the camera, unable to capture emotion, reduces the relationship to banality. Shouldn't Kessels have decanted the trite little archive into the Mediterranean? No, that would only have added to its pollution.
Jacques-Henri Lartigue signed his images of socialities disporting themselves on an unspoilt Riviera in the 1920s; beside his name in the margin he drew a blazing sun. Photography writes with light, so its practitioners are sun-worshippers; Lartigue's signature joyously privatised the burning, fertile star. Since then, the sun, as Pope says of his promiscuous heroine in 'The Rape of the Lock', has extended its franchise to 'shine on all alike'.
St Tropez, photographed recently by the painter Eric Fischl, is a scrum of sweating bodies with sand in their crevices. Nature has been colonised by commerce, and shops line the sand. Xavier Ribas intrepidly researches the wooded lay-bys where Spanish hookers sell alfresco sex. Broken bottles splinter underfoot, and sticky tissues - souvenirs, like photographs, of holiday romance - flap from the bushes.
At best, the Mediterranean now resembles a film set after the end of shooting. The exhibition includes Günther Förg's tour of the cliff-top villa in Capri where Godard filmed Le Mépris in 1963. In the film, Fritz Lang choreographed the Trojan war on a blazing roof terrace, while Brigitte Bardot, impersonating a modern goddess of love, seethed, writhed and pouted. The classical warriors and the cinematic idols have fled, and Förg photographs vacant windows that stare unseeingly at the flat, empty water.
Marc Räder presents a gruesomely glossy panorama of urbanisation on Majorca: a toytown of huddled villas, each equipped with a satellite dish so that the occupants can hide from the oppressive daylight and keep abreast of Big Brother . Two photographs of the same spot, taken more than a century apart, sum up the loss of paradise. Le Moine in southern France, photographed by Edouard-Denis Baldus in 1855, is a working valley that turns its back on the pebbly beach; a field where crops are cultivated has been squeezed into the crevasse. In Julie Ganzin's contemporary version, the peasants and their tilled earth have disappeared, and tourists prostrate themselves like broiling cadavers on a meagre slice of sand. A head sculpted from porous, eroded stone broods over both photographs: this anthropomorphic rock is the hooded monk who used to be the spirit of the place. Do any of the sunbathers realise that he's there, or know what Le Moine means? The exhibition's curator seems to share their blithe ignorance, since there's no reference to that tutelary presence in the accompanying brochure. The Mediterranean has been secularised.
The utopian dream remains alive, perhaps, for those who - like Mexican wetbacks wading over the Rio Grande into Texas - pay to be shipped across the Mediterranean in quest of economic benefits. Ad van Denderen, in photographs as grimy as newsprint, documents this clandestine trade in dreams. Iraqi Kurds receive rudimentary English lessons in a square in Athens, memoris ing a few garbled phrases scribbled on cardboard; later, after paying their fares to Albanian middle-men, they embark for Italy. Another gang of smugglers from Morocco dumps a boatload of illegal Africans on a beach in Spain. No Statue of Liberty raises a beacon to welcome the 'wretched refuse' of this 'teeming shore'.
Now that continents enviously and aggressively confront each other across it, the Mediterranean has become a militarised zone. Rosell Meseguer photographs defensive ramparts at Cartagena, built by Franco to protect Spain against invaders; in Guy Raz's photographs, innocuous towers for lifeguards in Tel Aviv and Gaza bristle like military lookouts, a reminder that the Mediterranean is the only natural and non-negotiable border Israel can claim.
Seas are supposed to join the lands that lie on either side of them, which is why the Greeks and Romans saw the Mediterranean as the earth's circulatory system. Today, the trench divides clashing cultures rather than uniting them.
For a few months of the year, our Mediterranean is an insanitary public bath. The rest of the time, it's a minefield.
Art: three to see
Edward Hopper Tate Modern, London SE1
Black President: The Art and Legacy of Fela Anikulapo-Kuti Barbican, London EC2
From Thursday until 24 October.
Mary Ellen Mark: American Odyssey and Twins Manchester Art Gallery