Is the future given? Cumulative impact of Climate change and MOSE closures on Venice and its lagoon.

Abstract

Abstract Measures to adapt to climate change (CC) might have secondary adverse effects. In Venice, the hotly debated MOSE system will prevent the flooding of the city, but also the water renewal of the lagoon, and since the frequency of the closures will increase with CC, concerns are raised on the fate of the lagoon ecosystem1,2,3. Nonetheless, a systematic downscaling of the cumulative impact of CC on the Venice lagoon under multiple emission scenarios and with or without the associated MOSE closures was not presented yet. Here we show that the systematic implementation of MOSE closures will efficiently buffer the CC impact on sea level rise, but not on temperature, and in any case at the cost of a significant increment in the lagoon water renewal time. However, results also emphasize that the future is not given, and a combination of more conservative emission scenarios and MOSE might be able to save both Venice and its lagoon. Model projections suggest that at the end of the century, under the RCP8.5 scenario the lagoon will stay close for about 260 days/year, lagoon water will exceed 30°C for more than 4 months, marine heat waves will dramatically increase, the average water renewal time will triplicate and more than 35% of the lagoon will need more than 20 days to renew its water. Those impacts will be much less severe, and possibly much less challenging for marine organisms, under the RCP4.5 scenario. Results emphasize the necessity of combining global mitigation and local adaption but stress the need of site-specific carefully planned adaptation measures. They also show that the future is not written, and we are still in time to adopt choices able to protect our environment.