City trees are important: they purify the air, reduce heat islands, help regulate the water cycle and provide immense health benefits. Yet unbridled development threatens the survival of the urban forest and the full range of ecosystem services it provides. The magnitude of these services is closely linked to the importance of the canopy, which is the area covered by treetops. It is generally characterized by an index that relates the sector covered by the tops to the total size of an area. A recent study of the natural canopy in the areas covering Québec City, Beaupré, l'Île d'Orléans, Lévis and other communities along the St. Lawrence River found it generates more than $1.1 billion in annual benefits.