The lagoon beyond Venice

A lagoon is an unstable condition. It lives between two exactly opposite threats: the rivers that fill it with silt, and the sea that empties it by carrying its bed away. Left to itself it becomes marsh, then meadow, then dry land, which is what happened to every other lagoon on the Adriatic. If the Venetian one is still here, it is because an administration looked after it without a break for eight centuries.

The work was enormous and it is almost invisible. Between the fourteenth and the seventeenth century the Republic diverted its rivers one by one, the Brenta to the south, the Sile and the Piave to the north, so that they discharged into the sea instead of the basin. It forbade clearing the banks, drove piles to hold the channels, dredged, scoured and surveyed. A dedicated magistracy, the Savi ed Esecutori alle Acque, had authority over anything touching the water, and its rulings overrode those of landowners. Then, in the eighteenth century, came the greatest work of all: the murazzi, a wall of Istrian blocks twenty kilometres long, laid along the barrier islands to stop the sea. It was finished in 1782. Fifteen years later the Republic was gone.

What you see from a vaporetto therefore has to be learned. The wide flat stretches of short grass that break the surface at low tide are the barene, natural salt marshes and the real lungs of the system: they take up the tides and feed the birds. The velme, lower down, appear only at the lowest waters. Between them wind the ghebi, tiny creeks through which the water comes and goes. And everywhere, planted in threes and fives, stand the bricole, bundles of oak piles marking the navigable channels. You travel the lagoon as you drive a road: outside the channel there is forty centimetres of water and then mud, and the propeller goes into it.

Nor is the history of this water Venice's alone. In the seventh century the seat of the duchy was at Eraclea on the northern shore, with Torcello as its great port and its bishopric; in the eighth the duchy moved to Malamocco on the Lido; it settled at the Rialto only in 810, after a Frankish attack. Each move followed the same logic: further from the mainland, closer to the middle of the water. The northern islands then emptied slowly, as the rivers brought their silt, malaria took hold and the port shifted, Torcello had as many as twenty thousand inhabitants and now has about ten.

That emptiness turned the lagoon into a reserve for functions the city did not want indoors. The glassmakers went out there because of fire; the mad and the infectious because of fear; then the powder magazines, the quarantine stations, the forts, the cemeteries, the convents. Things were also grown out there: Sant'Erasmo and the Vignole fed Venice vegetables for centuries and still do, a little. And fishing never stopped, at Burano, at Pellestrina, at Chioggia, and in the valli da pesca, embanked ponds where fish have been raised since the Middle Ages.

Today the balance has shifted again. Dredged shipping channels, sinking ground and rising seas mean that the sea the Republic walled out now comes in faster than it goes out. The modern answer is called MOSE: seventy-eight hinged gates lying on the floor of the three inlets, which rise when the forecast tide passes a set level. It is the same reasoning as the murazzi, two and a half centuries later, in steel instead of stone.