In recent years, processes of urbanisation have been changing the face of the world as we know it. A whole new landscape is being built, one with many more challenges and externalities than the previous one. Besides the correlation that these intense urbanisation processes have with climate change, more subtly, they relate to a conceptual separation of the natural and built environment. As of today, socio-economic growth cannot be met without environmental degradation, and while many efforts are present towards ecological conservation, none has proved adequate on a global and continental scale. A reason behind this ineffectiveness lies in a 'weak' understanding of the concept of sustainability, in which environment, society and economy are loosely interchangeable. Furthermore, the current administrative division of territories poses yet another challenge to the management of ecosystems which often have a cross-border nature. First, this thesis proposes a 'strong' sustainability concept, based on the coexistence of natural and human domains. Also, in the European context, a massive push to decrease our impact on the environment is being developed through the European Green Deal, which sets out to achieve climate neutrality by 2050. This thesis aims to exploit this urgent transition towards climate neutrality as a way to prepare for the following transition towards climate resilience, one in which built and natural environment will be able to adapt, together, to changing climate conditions. To do so, the two hypotheses of multifunctional and multi-actor development are advanced and applied to the context of the Scheldt estuary, at the border of the Netherlands and Belgium. Multi-functionality refers to the possibility of having multiple and different functions (environmental, social and economic) within single spatial developments. Multi-actor, instead, refers to the complementary need to include an extensive and diverse range of stakeholders in the decision-making process. These two hypotheses hold the potential to increase preparedness in an evolutionary-resilience perspective. In fact, opting for a multifunctional development that couples economic and environmental functions today might facilitate further adaptation measures needed in the future. Moreover, maintaining an active debate among different stakeholders about the long-term future of the region might boost innovation and increase the possibility of local populations to imagine different futures.