Our study is framed according to a transformational-sociocritical approach to an education for sustainable development (ESD) that, in particular, considers landscapes as learning contexts of potential use for fostering engagement in the areas of environmental protection and sustainable development. In keeping with this perspective, we surveyed students aged 16--17 years from the Lower St. Lawrence region (Quebec, Canada) concerning their knowledge and perceptions of issues pertaining to the St. Lawrence, the river facing them on an everyday basis, and about their role as citizens in that connection. In respect of theoretical considerations, we propose developing the concepts of relationships to knowledge, place identity and agency. An analysis of questionnaires (N=334) has served to: bring out the learnings and issues pertaining to the St. Lawrence River that students consider to be meaningful; characterise the various identity-centred relationships with this landscape; and define the eco-civic agency of the students surveyed. The results of this analysis then provide a basis for some proposals for an ESD curriculum relating to the St. Lawrence River that is rooted in students' concerns. While the environmental issues dealt with occur locally, the potential transfer of results into other curricula and educational contexts is also discussed.