May a highly touristic tropical island sustain water resources? Navigating troubled waters to berth on a safe shore.

While being a major economic development force for tropical islands, tourism may aggravate disturbances on local water resources (scarcity, pollution) and the surrounding ecosystem. In this work, we used a discrete events modelling approach to characterize trajectories of Cat Ba Island (Vietnam) and its ability to reach specific trajectories. We wanted to assess if a healthy social ecosystem could be compatible with tourism. We found that co-existence between water resources and tourism may be reached; moreover, a systemic state where ecosystem and sociosystem can sustainably coexist may be reached. The implementation of urban ecological infrastructure is a key process to shift from the present state towards more favourable states. Another significant result is that the departure from the present state to reach more favourable ones may lead to a transitory degraded situation; only by keeping in mind the systemic objective significant transformations can be carried out.