Wetlands

WHY RESTORE WETLANDS?

At TRCA, we are actively conserving existing wetlands and restoring lost wetlands in our watersheds.  Conserving or restoring wetlands is vital to the health of our watersheds and the communities that live in them.

The Toronto area has lost over 85% of its original wetlands to accommodate agricultural practices or land development. The resulting loss of habitat has been a huge detriment to fish, reptile, amphibian and bird populations, as species that were once widespread became confined to smaller and smaller fragments of habitat.

Wetland restoration achieves a number of benefits (ecological services), including:

  • Improved biodiversity
  • Increased wildlife habitat
  • Flood attenuation

  • Improved water quality
  • Recreational opportunities
  • Improved habitat connectivity

To mitigate the loss of wetlands and the ecological services they provide, TRCA strategically restores and creates wetlands throughout our jurisdiction using a planning tool developed by TRCA called Integrated Restoration Prioritization (IRP) and a planning process that includes: desktop analysis via digital elevation models, Arc Hydro modelling, use of LiDAR, historic and current orthophotography and field assessments.

IRP prioritizes restoration opportunities based on multiple objectives, and guides restoration planning and resource investment by selecting the wetland project that would have the most benefit to the people as well as the plants and animals that use them.
Please see below for examples of TRCA restored wetlands at inland and coastal sites.


Kortright Farm Wetland: Restored in Fall 2008

The Kortright Farm Wetland was created on an old agricultural field that was once drained for crop cultivation. The field had been left fallow for decades, but the underground tile drains continued to drain the wetland. There was renewed interest in bringing back farming in a manner that allowed for the wetland to re-establish. The project restored the lost wetland and farming was re-introduced.

This project showcases best management practices (BMPs) on near-urban agricultural land where both conservation and agriculture can co-exist. This is an example of how to successfully integrate agricultural spaces and wetlands to benefit our natural system and greenspaces.

Kortright Farm before restoration
Before restoration: Sept 2008. Fallow agricultural field.
Kortright Farm after restoration
After Restoration: June 2009. Wetland regraded. Tile drains removed. Wetland buffer planted.
Kortright Farm in June 2011
After Restoration: June 2011. Emergent vegetation established from existing seedbank. Agricultural plots established (background).

aerial view of Kortright Farm before restoration
Pre-restoration: March 2005.

aerial view of Kortright Farm after restoration
After Restoration: October 2009.


Corner Marsh – Restoration Work Completed in 2005

Corner Marsh is an 18-hectare lagoon within the Duffin’s Creek Coastal Marsh Complex, which is located in the Town of Ajax. As with many coastal marshes, controlled lake water levels, watershed influences and invasive species have all played a role in the degradation of Duffin’s Creek Marsh.

TRCA noted this degradation, including the decline of emergent vegetation within Corner Marsh, and in 2005 built a levy and installed a water control/fish passage structure to improve wetland management and directly address these issues.

This project has allowed for TRCA to implement adaptive management controls to isolate the marsh from watershed influences such as controlled lake water levels. The newly installed water control structure and fish gate allow TRCA to manage Corner Marsh water levels to mimic natural seasonal variations and exclude large carp from entering the marsh.

Through this adaptive management TRCA has restored historical emergent vegetation and reduced turbidity, which has made the surrounding area more desirable for wildlife (such as waterfowl, marsh birds, amphibians and fish) and increased the spawning, nesting and rearing areas around the wetland.

aerial view of Corner Marsh
Before: Corner Marsh in 2004. Levy has been built, but water control/fish passage structure not yet installed. Water is cloudy and turbid indicating poor water quality and emergent vegetation is sparse.

aerial view of Corner Marsh after restoration
After: Corner Marsh on August 14, 2008. Note the water clarity and established wetland vegetation in Corner Marsh compared to the rest of the marsh complex.

aerial view of Corner Marsh in 2010
After: Corner Marsh in 2010. Note that the water is clear and emergent aquatic vegetation and floating vegetation is well established.