Complex sentence: The "Cercles des jeunes Naturalistes" are most likely the first environmental organisation founded in Québec and are part of the Association francophone pour le savoir (L'ACFAS) since the official foundation in 1931.
Split into simpler sentences: The "Cercles des jeunes Naturalistes" is thought by many to be the first environmental organisation founded in Quebec. It has been associated with the Association francophone pour le savoir (L'ACFAS) since its official foundation in 1931.