In October 2020, Venice’s system built to protect the city from flooding using mobile barriers – known as MOSE – was tested and worked as designed. Water levels inside the lagoon remained stable when the tide reached 122 cm. Since then, the barriers have been raised multiple times when a tide of more than 110 cm is predicted.
But the system that saved Venice is unlikely to withstand the impact of climate change. Cultural leaders have voiced their concerns in this regard in a letter to prime minister Mario Draghi, reports Euronews.
Although it started operations in 2020, the MOSE system was designed in the 1980s, and our understanding and predictions about climate change have evolved since. Regional sea level rise projections published by the IPCC in 2021 predict mean sea level rise to reach 28-55 cm by 2100 in the most optimistic scenario, and 63-101 cm in the most pessimistic scenario.
The letter notes that “in their current operating mode, the existing barriers would need to be closed more than 260 times a year on average”, thus preventing the tidal exchange of water between the lagoon and the sea, resulting in the decay of life in the lagoon. In addition, Venice lacks a comprehensive sewage system and the tides remove waste from the lagoon. Ship traffic would also be hindered by barrier closures.
A study in Nature Geoscience shows that closing off the lagoon with the barriers is already causing some issues for the salt marsh ecosystems in the lagoon. The barriers prevent sediment transport during storm surges, something key to preserve these natural ecosystems; the authors conclude that unless barrier activations are reduced, the survival of the coastal wetlands is at risk.
In the hopes of mitigating damage to the lagoon, NGO We are here Venice (WahV) is working on a project that has received EU funding as part of the WaterLANDS work package, aiming to put the health of the lagoon system at the centre of plans and policies determining the future of Venice.
But a lot of energy went into make MOSE happen and it will be difficult to look beyond it. The system is still undergoing improvements, until at least 2023, to ensure its long-term efficiency, expected to reach 100 years. The MOSE can be effective and buy time to plan for the future, but adaptation strategies will have to diversify, taking into account the environmental and economic impacts of prolonged closure of the barrier defence system.
