Mountain-valley environments that have been or are in the process of in-migration, urbanization, and exurbanization are complex landscapes characterized by steep biophysical gradients and socioeconomic transitions, i.e., they are complex coupled human-natural systems. The initiators of MtnSEON are currently working together to develop the concept shaped to address the question: How can we reduce the vulnerability, improve resilience, and support sustainability of natural and human systems in complex mountain landscapes?