The role of ambiguity in the evaluation of the net benefits of the MOSE system in the Venice lagoon

Several environmental problems are complicated by ambiguity. Sea-level rise following climate change is one relevant example. In this paper, we apply a decision-making approach specifically designed to deal with ambiguity in order to evaluate the net benefits of the mobile barriers system (MOSE), which aims to protect the Venice Lagoon from periodic flooding. We show that the estimated impacts crucially depend on the level of optimism and pessimism of the decision maker and substantially differ from those calculated on the basis of the expected value. We also calculate the implicit ambiguity attitude of the decision maker.