Why Wetlands?

Marsh Photo by: Eric DresserNot land or water, but a fluid combination of both, wetlands are among the most productive habitats on Earth. Wetlands are all built on a simple foundation: water becomes trapped, either through poor drainage, periodic flooding or by coastal barriers such as sandbars, and a wetland -- that unique mix of land and water -- is born.

From this beginning, wetlands develop in a number of ways depending on local climate conditions, the availability of nutrients, and the geography and soils of a site. They also change over time: an open marsh may dry out enough to become a wooded swamp, only to revert back to open marsh again after heavy flooding.

In the past, wetlands were thought of as mosquito-infested wastelands that could only be dealt with by draining, filling or paving. Now, wetlands are increasingly recognized as much more dynamic, productive and diverse ecosystems. They are wildlife nurseries and nesting sites, feeding grounds and resting places, water filters and reservoirs. They help protect shoreline areas from storm damage, control and reduce flooding, clean sediment-laden waters, and attract fish, birds, amphibians, reptiles and mammals. They are also great places for people to explore and reconnect with nature.

Marsh Photo by: Eric Dresser Marsh Photo by: Eric Dresser Marsh Photo by: Eric Dresser

Yet, despite these values, wetlands continue to be lost at an alarming rate. They are drained for agriculture, filled for development, polluted by toxic runoff, invaded by exotic species, and damaged by artificial changes in water levels. Today, almost two-thirds of southern Ontario wetlands have been lost or severely degraded, while the health of those that remain continues to be threatened. If we continue to lose wetlands, a large and important piece of the natural system that keeps our world healthy will disappear.

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Wetland Functions and Values

Wetlands represent one of the most important life support systems in the natural environment. Wetlands provide:

  • A water filtration system...removing contaminants, suspended particles and excessive nutrients, improving water quality and renewing water supplies.
  • An irreplaceable habitat...nesting, feeding and staging ground for several species of waterfowl and other wildlife such as reptiles and amphibians, and also for many species at risk.
  • A high quality spawning and nursery area for many species of fish.
  • Natural shoreline protection...protecting coastal areas from erosion.
  • A reservoir...helping to control and reduce flooding through water storage and retention.
  • A source of oxygen and water vapour...playing a vital role in the natural atmospheric and climatic cycles.
  • Recreational activities...hiking, birdwatching and fishing.

People in Canoe Photo by: Matt Young Photo courtesy of: U.S. EPA
Beaver Photo by: Eric DresserStream Photo by: Eric Dresser

The functions and values of wetlands are becoming increasingly clear to scientists and those who manage wetlands. However, the difficulty faced by these individuals is how to communicate these functions and values in a way that will be understood by land owners, government regulators and the public.

In other sectors of the economy, the most common way of demonstrating the value of something is to quote a price. But what is the price of a wetland? There is an entire branch of economics emerging that is devoted to the assessment of ecological value. For more information on how to value wetlands, see Putting an Economic Value on Wetlands - Concepts, Methods and Considerations.

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Wetland Stresses

Low Water Photo by: Maggie YoungThe importance of wetlands to both humans and ecosystems is increasingly being recognized; however, there are many direct and indirect stresses that continue to threaten habitats. Stresses can also be classified as natural or human-induced. Many wetlands are able to adapt to natural stresses, such as storms, ice damage and low water levels. Unfortunately, human-induced stresses often occur so quickly and drastically that wetlands are not able to fully recover. Working Around Wetlands is an informative brochure that provides basic information on how landowners can minimize stress to wetlands when working in close proximity to wetlands on their property.

Direct Stresses

Dredging Photo Courtesy of U.S. EPA Peat Extraction Photo by: John Mitchell

Shoreline Hardening Photo by: Graham BryanDirect stresses are those that occur within a wetland, such as dredging, filling, draining, and invasive species. They are usually human-induced, highly visible and can result in rapid changes to wetlands.

Pollution Photo courtesy of U.S. EPAGreat Lakes coastal wetlands are often located at river mouths and in protected areas which are also favourable places for harbours. As a result, dredging has historically occurred in wetland areas to allow the safe entry of boats. Deepening the water and removal of sediments can result in the destruction of wetland habitat. In the same way, draining and filling of small wetlands for urban development and to increase agricultural area results in significant losses of wetland area and function each year.

Invasive species are those that reproduce so aggressively that they displace native plants in the area that they have become established. Common invasive wetland plants include Purple Loosestrife and Eurasian Water Milfoil. Aggressive fish and wildlife can also be a problem. Carp, a fish introduced from Europe, damages wetland ecosystems while feeding and spawning by uprooting submerged vegetation and increasing the cloudiness of the water which decreases light penetration required for plant growth.

Indirect Stresses

Indirect stresses are often less pronounced, causing changes to occur to wetland function and vegetation communities over a longer period of time. It is often difficult to pinpoint the exact source of these stresses.

Exotic Species Photo courtesy of U.S. EPAIndirect stresses include runoff from upstream agricultural practices, sewage treatment plants and industrial sources which can cause loading of nutrients, sediments and toxic chemicals in downstream wetlands. Due to the collective contribution of sources, it is often difficult to remediate these problems. Fortunately, wetlands are able to assimilate some nutrients and toxic chemicals through plant uptake and the interaction of flowing water with microbial communities active in the wetland soils. These tiny organisms are able to transform and break down nutrients and some toxic chemicals.

Shipping Photo courtesy of U.S. EPAAnother indirect stress is lakewide water level regulation, which occurs on Lake Superior and, to a more significant extent, on Lake Ontario. Regulation is carried out to maintain water levels in the Great Lakes at a level appropriate to accommodate navigation, shipping, hydroelectric power and shoreline landowners. However, this means less natural variability in water levels, to which coastal wetlands have adapted over many years. Alternating high and low water levels often lead to more diverse plant communities: thus, consistent high or low water levels can cause less diverse systems by excluding those species that rely on periodic changes in water level.

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Habitat Types and Species Protected

Great Lakes Wetlands Conservation Action Plan: a partnership to sustain Great Lakes WetlandsThere are a wide variety of wetland habitats and species that are protected throughout the Great Lakes by partnered conservation initiatives, including the Great Lakes Wetlands Conservation Action Plan (GLWCAP) and the Eastern Habitat Joint Venture. The five major freshwater wetlands types are represented in protection activities: marsh, swamp, bog, fen, and shallow open water. For each of the habitat types, examples of secured sites and some of the protected species found within them are provided in the table below.

For more information about some of the wetland species listed in the table (and many other species found in Canada), explore the following Canadian Wildlife Service wildlife information sources:

Hinterland Who's Who


Species at Risk in Ontario


Wetlands Habitat Types
These wetlands are periodically or permanently covered by standing or slowly moving water. Marshes are rich in nutrients and are characterized by an emergent vegetation of reeds, rushes, cattails and sedges. Water remains within the rooting zone of these plants for most of the growing season. Marshes are the most productive wetlands habitat.

Secured Sites
Photo by: Ducks Unlimited
Long Point Marsh *
Matchedash Bay *
St. Clair River
Detroit Rivert
Dunnville Marshes *T
Wainfleet Bog *
Niagara Rivert
Metro Toronto's Waterfrontt
Oshawa's Second Marsht
Hamilton Harbourt
Bay Of Quintet
Rondeau Bay *T
Big Sandy Bay *
Hoasic Creek *
Pigeon Marsh *
Port Franks Wetlands And Dunes *
Riley Marsh*

Species Protected
Bald Eagle, Forester's Tern, Loggerhead Shrike, Prothonotary Warbler, Red-shouldered Hawk, Sandhill Crane, White Pelican, Least Shrew, Eastern Hognose Snake, Fox Snake, Queen Snake, Eastern Spiny Softshell Turtle, Spotted Turtle, Fowler's Toad, Orangespotted Sunfish, Spotted Gar


Wetlands Habitat Types
Swamps are dominated by shrubs or trees. They may be flooded seasonally or for long periods of time. Swamps are both nutrient rich and productive. Vegetation may be composed of coniferous or deciduous forest or tall thickets. Swamps are most common in temperate areas of Canada.

Secured Sites
Swamp Photo
North Cayuga Slough Forest *
Brockville Long Swamp Fen *
Minesing Swamp *
Oxley Poison Sumach Swamp *
Westplain Mud Lake *
Hoasic Creek (Dupont Provincial Nr) *

Species Protected
American Ginseng, Dwarf Hackberry, Prairie-Fringed Orchid, Least Bittern, Loggerhead Shrike, Red-shouldered Hawk, Blanding's Turtle, Spotted Turtle


Wetlands Habitat Types
Bogs are peat-covered wetlands in which the vegetation shows the effects of a high water table and a general lack of nutrients. Due to poor drainage and the decay of plant material, the surface water of bogs is strongly acidic. Although they are dominated by sphagnum mosses (peat) and heath shrubs, bogs may support trees. More common in northern Ontario and rare in the south, bogs are the least productive of all wetland types.

Secured Sites
Photo by: Nancy Patterson
Wainfleet Bog*
Fairlan Lake Bog

Species Protected
Virginia Bartonia, Many-fruited False Loosestrife, Marsh St. John's wort, Pin Oak, Southern Tickseed, Swan's Sedge, Tapered Rush, Toadflax, Torrey's Mannagrass, Virginia Yellow Flax, Yellow-breasted Chat, Opossum, Black Rat Snake, Massasauga Rattlesnake, Spotted Turtle, Fowler's Toad


Wetlands Habitat Types
These wetlands are characterized by a high water table with slow internal drainage by seepage down low gradients. Their surface waters may be acidic or alkaline. Fens are not as low in nutrients as bogs and as a result are more productive. Although fens are dominated by sedges they may also contain shrubs and trees. Like bogs, they are more common in the north.

Secured Sites
Fen Photo
Brockville Long Swamp Fen *
Westplain Mud Lake *
Alliston Basin Wetlands *

Species Protected
Handsome Sedge, Prairie-fringed Orchid, Twin-scaped Bladderwort, Cooper's Hawk, Blanding's Turtle, Spotted Turtle, Olive Hairstreaked Butterfly

Shallow Open Water

Wetlands Habitat Types
These wetlands include potholes and sloughs (ponds), as well as waters along rivers and lakeshore areas. They are usually relatively small bodies of standing or flowing water commonly representing a transitional stage between lakes and marshes, or between spring high water levels and levels during the remainder of the year.

Secured Sites
Photo by: Environment Canada
Alliston Basin Wetlands*

Species Protected
American Ginseng, Riverbank Wild Rye

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Lands that are seasonally or permanently covered by shallow water, including lands where the water table is at or close to the surface. The presence of abundant water causes the formation of hydric soils and favours the dominance of either hydrophytic or water-tolerant plants. The five major types of wetlands are: marshes, swamps, bogs, fens, and shallow open waters.

Natural Wetlands

A wetland dominated by native biota and occurring within a biophysical system which has developed though processes with minimal human intervention.

Disturbed Wetlands

A wetland that has had its functions altered, directly or indirectly, by external human or natural forces.

Enhanced Wetland

An existing wetland where some planned activity by humans addresses the stresses or limitations to change one or more functions or values.

Wetland Rehabilitation

Improvement of the functions or values of a degraded wetland.

Wetland Restoration

Modification of the existing function and structure of a wetland's habitat so that it is similar to historical conditions.

Wetland Creation

The conversion of a persistent upland vegetation community or ephemeral shallow water area into a permanent wetland where no previous wetland existed.

*Definitions from Temperate Wetland Restoration Guide.

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