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  • Are more common in northern Ontario.
  • Have surface waters that may be acidic or alkaline.
  • Have a high water table with slow drainage.
  • May contain shrubs and trees but are dominated by sedges.
  • Are more productive than bogs because they are not as low in nutrients.

Fens occur in poorly drained freshwater regions. Although they can be found throughout Canada, they are most common in arctic and subarctic regions.


Muskoka Heritage Areas
classified as having a fen:
* Are also classified as being provincially significant wetlands



Fen Characteristics

Fens have a high water table and some flow-through, but not much fresh water. They absorb massive amounts of water and are exceptional at preventing floods, supplying a constant flow of water and water filtration.


Vegetation in a Fen

Fens are dominated by grasses, sedges, and some mosses. Trees are more common in a fen than in a bog. There are more nutrients in a fen compared to a bog and the vegetation and organic matter fall to the bottom rather than float on top. Low oxygen levels and lack of bacteria in fens means that plant and animal matter decomposes very slowly.


Wildlife Inhabitants in a Fen

Fens contain a variety of species that help make up a productive ecosystem.

There is an abundant insect population consisting mainly of deerflies, horseflies and mosquitoes. Butterflies and moths associated with grasses and sedges are also present.

A variety of amphibians that breed in local ponds can usually be found in fens, including turtles and frogs.

Bird species include the Virginia rail, the Yellow warbler and the Swamp sparrow, as well as other swallows and flycatchers.

Mammals include Cinerous shrew, Water shrew, Star-nosed mole and Muskrat. In addition, many other species may be encountered entering the fen from adjacent habitats.

MNR Wetland Fact Sheets


What are Wetlands? 
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 Important 
Surface water runoff may contain sediments, excess nutrients, viruses and pathogens and/or a variety of chemicals. A wetland acts like a filter to remove sediments, absorb nutrients and biologically change many chemicals into less harmful forms.

Significant Wetlands and the Ontario Wetland Evaluation System 
Provincially Significant Wetlands are those areas identified by the province as being the most valuable. They are determined by a science-based ranking system known as the Ontario Wetland Evaluation System.

Wetland Restoration 
Ontario is home to approximately 24% of Canada's wetlands and 6% of the world's wetlands. Estimates of wetland extent in Ontario range from 24 million to 29 million hectares, or 22-27% of the area of the province.