Lac Saint-Pierre World Biosphere Reserve

Lake Saint-Pierre, a natural widening of the Saint Lawrence River between Trois-Rivières and Sorel, conceals an ecosystem of exceptional richness, whose recognition by UNESCO as a World Biosphere Reserve testifies to the global ecological importance of this floodplain. The natural mechanism underlying this richness rests upon the seasonal alternation between spring flooding and summer drying of the riverbanks, creating a land-water transition zone particularly conducive to biological productivity and the formation of marshes and wetlands offering shelter, food, and protection to exceptionally diverse wildlife, including North America's largest heron colony. Each spring, this phenomenon attracts nearly one million migratory birds to the plains of Lake Saint-Pierre, including up to 400,000 snow geese that, after a 900-kilometre flight from the American east coast where they have wintered, make an extended stopover to feed on corn residue in the surrounding agricultural lands before resuming their migration to their nesting grounds in the Arctic. This ornithological spectacle, typically at its peak in mid-April, transforms the sky into an impressive aerial ballet of these entirely white birds, distinguished only by the black tips of their wings, which have become emblematic symbols of the floodplain and a major ecotourism attraction for the region.