Estuaries occur where rivers meet the sea and salt water mixes with fresh as the tide goes in and out. Because so many rivers and streams flow into the waters of the Salish Sea, the whole area is a huge estuarine system. Estuaries are the most biologically productive ecosystems on earth, more productive than grasslands, forests, and even areas of intensive agriculture.
Although estuaries make up less than 3% of BC’s coastline (as of 2004), 80% of our wildlife depend on estuaries for survival. For example:
- River nutrients are passed up the foodchain to predators such as bald eagles.
- Migrating birds need extensive wetlands when winter snow and ice cover fields, ponds and streams.
- After hatching upstream, salmon fry depend on estuaries to grow and acclimatize to salt water before heading out to sea.
- Salmon also depend on estuaries at the end of their life cycle, when they return to rivers to spawn.
Estuaries are essential to humans as well. Estuary silt is an irreplaceable pollution filter, cleansing inshore waters and removing toxins such as sulphur dioxide from the air.
The Fraser River delta is our region’s largest estuary. It is the only coastal waypoint of its kind between California and Alaska. Birds from 20 countries and three continents depend on it for overwintering or for rest and sustenance during their long annual migration along the Pacific Flyway.
BC Nature Trust has identified three nearby estuaries as being internationally significant for migratory birds:
- Comox (1300 hectares)
- Denman Island (2500 hectares)
- Cowichan-Chemainus (2000 hectares)