One of the main environmental problems in Venice is the moto ondoso – wave movement.
It is mostly caused by taxis and tourist boats, to a lesser extent by vaporetti (water buses) and private boats.
The constant churning of the water causes erosion of walls, side walks and quays, slowly but surely demolishing the city. You just have to row around the city at low tide to see the damage.
This is how the city appeared on October 3rd, 2015. See if you can spot the gondola.