Venice Lagoon: salt marshes between carbon conservation and coastal management challenges

The salt marshes of the Venice Lagoon, essential coastal ecosystems, represent a crucial resource in the fight against climate change. A study conducted by Alice Puppin, together with Davide Tognin, Massimiliano Ghinassi, Chiara D’Alpaos, Marco Marani, and Andrea D’Alpaos from the Department of Geosciences at the University of Padova, and the research group Estuarine & Fluvial Hydrology, Ecomorphodynamics & Sedimentology, highlighted their role as “blue carbon reserves”. Published in Earth’s Future, the study analyzes the ability of these areas to accumulate and store carbon dioxide, effectively reducing CO₂ levels in the atmosphere.
A hidden carbon reserve
The research examined ten salt marshes in the lagoon, collecting soil samples up to one meter deep. The results show that salt marsh soils store 17,108 tons of carbon per square kilometer and accumulate around 85 tons per square kilometer annually. In practical terms, this is equivalent to the carbon absorption capacity of 130,000 trees per square kilometer.
“The term ‘Blue Carbon’ was coined in the early 2000s to refer to organic carbon captured by marine and coastal ecosystems,” Puppin explains, “a concept complementary to the ‘Green Carbon’ of terrestrial forests.” She emphasizes that more than half of global carbon sequestration happens thanks to marine and coastal ecosystems, a contribution often underestimated.
The impact of coastal management
The study highlights how tidal regulation strategies, such as the Mo.S.E. system, could disrupt this balance. According to the collected data, these interventions reduce sediment transport—essential for the vertical accretion of salt marshes—thus lowering their carbon sequestration capacity by 30%.
“The Mo.S.E., designed to protect Venice from flooding, could significantly reduce the CO2 sequestration potential of salt marshes by limiting sediment supply during storm surges,” Puppin states. This reduction not only affects climate mitigation capabilities but also deprives the region of an increasingly valuable environmental resource.
A research with broad implications
Beyond CO2 sequestration, salt marshes provide a variety of ecosystem services, including coastal protection and biodiversity enhancement. “Attributing an economic value to the services provided by salt marshes,” Puppin adds, “can encourage their conservation and restoration. For example, their CO2 sequestration capacity is estimated to be worth nearly €1 million annually, based on current European carbon market prices.”
Looking to the future
The study calls for reconsidering the balance between flood protection and environmental conservation. “Salt marshes are not only a tool to mitigate climate change,” Puppin concludes, “but also a means to preserve numerous environmental benefits, from increased biodiversity to water purification and protection against erosion.”
This interdisciplinary work demonstrates how an integrated approach can ensure sustainable management of the Venice Lagoon, enhancing the contribution of natural ecosystems in the fight against climate change.
Venice Lagoon: a miniseries to find out this unique environment
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