Ontario has four different types of wetland:

Wetlands - Bog
A Black Spruce bog (Photo: Sam Brinker)

Bogs are known as peatlands. They actively accumulate peat (partially decomposed plant material) and act as long-term sinks for carbon dioxide in the atmosphere, helping to fight climate change.


Bogs receive their water from rainfall, are typically low in mineral nutrients and strongly acidic. Bogs are usually covered with a carpet of Sphagnum moss.


Other vegetation includes stunted black spruce trees, heath plants such as laurels and blueberries, and carnivorous plants such as sundews and pitcher plants.


Wetlands - Fen
Scattered tamarack trees in a sedge fen (Photo: Sam Brinker)

Fens, like bogs, are also 

referred to as peatlands. They tend to be less acidic and have more nutrients than bogs.


They form in areas where groundwater discharges to the surface.


Typical fen vegetation includes sedges and mosses, along with some grasses, reeds, low shrubs, tamarack and white cedar, sundews, pitcher plants, and orchids.




Wetlands - Marshes
Cattails grow in clumps amid floating water lilies in this marsh
Photo: Donald Kirk

Marshes are periodically or permanently flooded with water.


Most marsh vegetation consists of non-woody plants such as cattails, rushes, reeds, grasses, and sedges. Floating and submerged plants like water lilies and pondweeds can be found in open water marshes.


Many Great Lakes coastal marshes provide important habitats for fish, waterfowl and a variety of rare species.





Wetlands - Swamp
This swamp has little to no standing water, but the plants and trees growing here indicate that the soil is very wet
Photo: Sam Brinker).

Swamps: Common in both southern and northern Ontario, swamps are dominated by woody plants (trees or shrubs).




They are very diverse, exhibiting a wide variety of vegetation communities, ages and ecological settings.









Wetlands - button bush
This buttonbush shrub swamp is an important breeding site for frogs (Photo: Erin Sanders)

Ontario contains one-quarter to one-third of Canada's wetlands and 6% of the world's wetlands.



It is estimated that there are 24 million to 31 million hectares of wetlands in Ontario, or 22-29% of the province.



Although wetlands are still plentiful in Northern Ontario, over 70% of the wetlands that once occurred in Southern Ontario have been lost.



The Great Lakes are a globally significant ecosystem that supports many coastal wetland habitats, some with globally rare animals and vegetation communities.