What is a wetland?
A wetland is any area of land that is covered with shallow water for part of the
day or year. Freshwater wetlands usually form in spring, when rivers and streams
overflow with melting snow. Saltwater wetlands are primarily caused by ocean tides
and sandbars.
A unique mix of land and water, wetlands harbour dynamic and diverse ecosystems.
What is an ecosystem?
An ecosystem is a biological community of plants, animals and microorganisms and
their physical environment or habitat. It can be as big as the Sahara Desert, as
small as a mud puddle, or somewhere in between like the Science Centre marsh. No
ecosystem community can support more organisms than its food, water and shelter
can accommodate. Food and territory are often balanced by natural phenomena such
as fire, disease and number of predators. In an ecosystem, every organism has a
role to play.
Wetland ecosystems perform a variety of uses:
- a bird, animal and insect sanctuary for feeding, nesting and resting
- a fish spawning and nursery area
- a natural reservoir that controls spring flooding
- a water filter that sifts out sediments and contaminants
- a defense against soil erosion from storms and thaws
- a source of oxygen and water vapour
- a place to enjoy nature and recreational activities
Despite the value of wetlands, they continue to be drained, filled, polluted, invaded
and damaged. Today, nearly two-thirds of southern Ontario wetlands have been destroyed
or degraded.
What is a marsh?
Wetlands are one of nature's most vital life support systems. They include marshes,
swamps, ponds, bogs and fens - ours is a marsh.
Marshes are the most productive wetlands habitat, rich in nutrients and water-loving
vegetation such as reeds, rushes, cattails and sedges. Inhabited by a wide variety
of species, marshes are periodically or permanently covered by standing or slowly
moving water.
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Photos taken in the Ontario Science Centre marsh by Alex MacDonald.
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Dip into our marsh's past
Over time, rivers change their routes. That's what happened to the Don River, the
source of water for the marsh at the Ontario Science Centre.
Once upon a time, the Don River meandered right where our marsh is now, in a horseshoe
shape known as an "oxbow". But as the Don carved out a different path,
the oxbow slowly filled in with sediment and dried up - except in spring when river
meltwater temporarily overflowed into the oxbow to create a marsh.
A few decades ago, an earthen dam was built to keep the spring runoff from draining
away during summer. This allowed the Science Centre's marsh to remain wet year-round,
although water levels still dropped between spring and fall.
Then, in 1998, Ducks Unlimited, the Toronto and Region Conservation Authority (TRCA)
and the City of Toronto Parks and Recreation Department replaced the original dam
with a permanent one that can be opened when necessary. This meant our marsh was
now an officially reclaimed wetland.
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