Wetlands are defined as lands that are saturated with water long enough to cause the formation of waterlogged (hydric) soils and the growth of water-loving (hydrophytic) or water-tolerant plants. Wetlands are transitional habitats, often forming the connection between aquatic and terrestrial ecosystems. They can occur where the water table is at or close to the surface, in low-lying locations, or along the edges of lakes and rivers. Many wetlands are permanently flooded, while others flood only periodically in the spring or fall – you can often walk through such areas in the summer without ever getting your feet wet!
Four major types of wetlands are recognized in Ontario: marshes, swamps, fens and bogs.
Marshes are wetlands that are periodically or permanently flooded with water. Marsh vegetation typically consists of non-woody plants such as cattails, rushes, reeds, grasses and sedges. In open water marshes, floating and submerged plants such as water lilies and pondweeds can be found. Marshes are fairly common throughout Ontario, with the most productive ones occurring along the shorelines of the southern Great Lakes.
Swamps are wooded wetlands that are often flooded for a portion of the year. Swamp vegetation is dominated by trees, including both coniferous and/or deciduous species, and tall shrubs, such as willows, dogwood and alder. Common throughout Ontario, swamps are incredibly diverse, exhibiting a wide array of vegetation, age and ecological settings.
Bogs are peat-filled depressions that receive their water and nutrients from rainfall. Peat consists of partially decomposed plants. Bogs are extremely low in mineral nutrients and tend to be strongly acidic. They are typically covered with a carpet of Sphagnum mosses. Other vegetation includes stunted black spruce trees, heath plants such as laurels and blueberries, and carnivorous plants such as sundews and pitcher plants. Bogs can take thousands of years to form and are extremely rare in the southern part of the province, though common throughout northern Ontario.
Fens, like bogs, are peatlands – that is, wetlands that accumulate peat. They are located in areas where groundwater discharges to the surface. Fens typically have more nutrients than bogs, and the water is less acidic. Typical fen vegetation includes sedges and mosses, along with some grasses, reeds, low shrubs, tamarack and white cedar, sundews, pitcher plants and orchids. While fairly rare in southern Ontario, fens are quite common in Northern Ontario.