MOSE Venezia

Venice, Italy, a city that has thrived around its water and lagoon since its origins in the 5th Century, is now confronted with a pressing adversary—the very element that once facilitated its prosperity. The frequency and intensity of floods in Venice have been escalating, posing an alarming threat to this already-vulnerable city. While seasonal high tides, known as "acqua alta," have long been a part of life in Venice, they have become increasingly severe and record-breaking. In November 2021, a storm surge reached six feet, resulting in approximately 90% of the city being flooded. The sirens warning of more water over the course of four days underscored the gravity of the situation. This concerning phenomenon has led many, including climate scientists, to view Venice as an example of what’s to come elsewhere as we see more and more places succumbing to the impacts of anthropogenic climate change.

In response to these concerns, MOSE Venezia was developed. Named after Moses, the project had been 30 years in the making, with construction finally commencing in 2003 and reaching completion by the end of 2021. MOSE aims to safeguard Venice by employing gate barriers (effectively flood gates) positioned along three inlets connecting the Venetian lagoon to the Adriatic Sea that can block high tides and storm surges from entering the city. This ambitious project, costing a staggering $6 billion, works using these gate barriers that have been strategically positioned on the seabed, raised when tides reach a critical level of 3.5 to 3.6ft (signalling the onset of ‘acqua alta’). While MOSE appears promising in its ability to mitigate the impact of surges, concerns have been raised regarding its potential detrimental effects on the delicate ecosystem of the Venetian lagoon.

One of the issues is the ecological impact of MOSE on the lagoon's biodiversity and ecosystems. The lagoon sustains a diverse population of halophytic plants, crabs, and fish, while its salt marshes play a vital role in carbon sequestration. These marshes remove approximately 370 tons of CO2 per square kilometres annually, a rate 50 times greater than that of tropical forests. However, due to human activity, salt marshes, including those within the lagoon, have already experienced significant decline. Intervening with MOSE to protect the city may inadvertently exacerbate the ecological challenge while attempting to combat another. The delicate balance between protecting Venice and preserving its ecosystem remains a critical concern.

While MOSE has demonstrated its effectiveness thus far, successfully shielding the city and its inhabitants during high tides, there are uncertainties regarding its long-term viability. Sea levels are projected to rise by at least another two feet by the end of the century, which raises questions about MOSE's ability to continue protecting Venice in the face of such challenges. Furthermore, the ongoing maintenance and necessary adaptations to the system add to the already substantial costs associated with the project. For example, estimates currently place each use (‘raising’) of MOSE at $300k. How feasible is this, really?

Venice's experience with climate change and its reliance on the MOSE Venezia project have positioned it almost as a "poster child" for the global challenges posed by anthropogenic climate change. The recurrent floods in Venice serve as a forewarning to coastal and low-lying communities worldwide that are similarly vulnerable to the escalating impacts of climate change, while also capturing the capabilities of engineering in providing potential solutions. While MOSE offers a temporary solution, concerns persist regarding its environmental consequences, long-term efficacy, and the financial burden it entails.

The implications of these recurring floods prompt questions about the future of Venice too. Will more people be compelled to abandon the city, potentially transforming it into a ghost town or a mere museum? The mayor Luigi Brugnano envisions a different path, aiming to make Venice a living laboratory—a place where innovative solutions are developed to save the city and, in turn, contribute to the preservation of our planet. Venice's struggle serves as a powerful symbol, reminding us of the challenges faced by coastal communities around the world and the urgent need to safeguard our planet's future.

Written by Heidi Surfleet

References:

60 Minutes climate archive: Venice is Drowning (60 Minutes on YouTube, 2021)

Harlan, C. and Pitrelli, S. (2022) ‘An engineering marvel just saved Venice from a flood. What about when seas rise?’, The Washington Post, 26 November.

‘Saving Venice from flooding may destroy the ecosystem that sustains it’, Frank Viviano (2022) for National Geographic

https://www.mosevenezia.eu/project/?lang=en