In Québec, climatic change scenarios (CC) forecast an increase of 1-4oC in mean annual temperature by 2030 (IPCC, 2001), with important effects on the regional water budgets. In spite of these anticipated consequences, the CC phenomenon remains misunderstood by teenagers (Quebec and New Brunswick) (Pruneau et al., 2001), stressing the necessity to educate them to CC. The teaching kit (teaching guide and poster) we developed for 1st cycle in high school represents a concrete example of the effects of CC on the St. Lawrence River. The teaching guide comprises a series of questions for students and a list of Websites to answer them. The poster will describe the effects of climate on St. Lawrence ecosystem components (production in progress). An interdisciplinary and ecosystemic approach is privileged, which also integrated the 5 domains of Ministère de l'Éducation du Québec (MEQ) training program (Mathématiques, Sciences et Technologie, Univers Social, Langues, Développement Personnel et Arts). The concept was presented with success to high school groups (age 13) from College Notre-Dame in Montreal during spring 2003.