KEY FINDING 5. Coastal ecosystems, such as estuaries, salt marshes, and mud flats, are believed to be healthy in less-developed coastal areas, although there are exceptions. In developed areas, extent and quality of coastal ecosystems are declining as a result of habitat modification, erosion, and sea-level rise.
This key finding is divided into five sections:
- Key finding overview (this page)
- Atlantic coastal ecosystems
- Pacific intertidal wetlands
- Hudson Plains salt marshes
- Eelgrass meadows
Coastal ecosystems occur at the interface between land and sea. They include intertidal zones, estuaries, salt marshes, mud flats, seagrass meadows, beaches, cliffs, banks, and dunes. Bounded by three oceans, Canada has the longest marine coastline in the world, with 29% of the world's total coastline.1 Coastal ecosystems are important as they are particularly productive environments. Canadian coastal ecosystems support a diversity of marine and terrestrial species, including members of all major groups of marine organisms, approximately 1,100 species of fish, and numerous marine mammals, birds, plants, and invertebrates.2
Developed coastlines In Canada, as elsewhere in the world, increasing human population and development of coastal regions is resulting in ongoing loss and degradation of coastal ecosystems. Infrastructure, industry, commercial activity, and settlements near the coast have depleted and altered natural systems and made coastlines more sensitive to erosion. Wetlands, including salt marshes and estuarine habitat, were severely depleted during early development of the populated areas of Canada's east and west coasts. Further losses will occur as sea levels rise, especially where development now leaves only a narrow margin of habitat. Inventories are available of extent and sensitivity of some coastal ecosystems,3-5 but information on past and current rates of loss and alteration is sparse.
Less developed coastlines Sea-level rise and changes in sea ice are examples of emerging stressors that are altering ecosystems in coastal areas that are not greatly affected by development. For example, along the southwestern, western, and eastern coasts of Newfoundland, the combination of rising sea level and changing offshore winter ice conditions, along with increased human use of the coast for residences and tourism, has resulted in widespread acceleration of erosion and degradation of dunes and coastline.6-9 In Quebec, from the upper estuary to the Gulf of St. Lawrence, rates of coastal erosion measured from 1990 to 2004 were higher than those measured before 1990. This was likely influenced by changes in climate-related processes such as ice scouring and wave action.10 Erosion in sensitive areas of the Beaufort Sea coastline may also increase because of reduction in sea ice, melting ground ice, and increase in storms11 as is currently happening along the coast of the Alaskan Beaufort Sea.12
It is estimated that up to 65% of Atlantic coastal marshes have been lost since the 1700s as a result of dyking and drainage for agriculture and settlement, and more recently for industrial and recreational development as well.15, 16
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