1. Project Title: Wetland Plantings Within the Mimico Creek Estuary, Humber Bay Park, City of Etobicoke
2. Contact
Jennifer Vincent
Metropolitan Toronto and Region Conservation Authority
5 Shoreham Drive, Downsview, Ontario M3N 1S4
Tel.: (416) 661-6600 ext. 349; FAX: (416) 661-6898
3. Agencies Involved
Metro Toronto and Region Remedial Action Plan
Environment Canada's Great Lakes Cleanup Fund
Ministry of Environment and Energy
Ministry of Natural Resources
Municipality of Metropolitan Toronto
4. Restoration Goal
To establish a diverse and healthy wetland plant community within the Mimico Creek Estuary. To evaluate different planting techniques and wetland plant species, determining the most appropriate methods.
5. Project Type
Creation of new habitat.
6. Background and Rationale
Wetlands represent a very small percentage of our total land area, yet they provide a haven for an unusually large percentage of our plants, birds and wildlife. One third of North American bird species, for example, appear to rely directly on wetlands for some resource.
Coastal wetlands are a critical component of the Lake Ontario shoreline providing habitat for fish and wildlife. Historically, most rivers within Metro Toronto supported estuary wetlands, the successful recreation of these river mouth marshes will be critical in the restoration of degraded Great Lakes habitat.
The Mimico Creek estuary has been altered by urbanization, currently
residing within the
lakefilled Humber Bay Park in the City of Etobicoke. The wetland
project is located within an embayment immediately south of Lakeshore
Blvd. on the west side of the creek. Factors that appear to be
limiting natural colonization include turbidity, lack of seed
stock, fluctuating lake levels, ice shear, and wildlife predation.
It is believed that once a community is established, it will be
able to withstand these pressures. A plant establishment program
began in August of 1992 and was completed in the fall of 1993.
7. Regulatory Considerations
A number of approvals from Federal, Provincial, and Municipal agencies were obtained to meet legislative requirements before conducting this project. The following outlines each Federal, Provincial, and Municipal agency involved in the approval process.
Federal
Environment Canada
Summaries of Initial Assessment as per Federal Environmental Assessment Review Process
Department of Fisheries and Oceans
Fisheries Act
Provincial
Ontario Ministry of Environment and Energy
Provincial Environmental Assessment Act
Ontario Ministry of Natural Resources
Fisheries Act
Lakes and Rivers Improvement Act
Public Lands Act
Municipal
Metropolitan Toronto Parks and Property
Waterfront Agreement 1972
Metropolitan Toronto and Region Conservation Authority
internal development project approvals
8. Criteria
Initial preference should be given to those wetland plant species
that can withstand more rigorous environmental conditions (eg.,
Typha sp.). These plants will create the more sensitive
environment needed support a more diverse plant community. Once
these plants are established, more
environmentally sensitive material can be planted.
Ideal emergent planting conditions include:
water levels less than 30 cm
enriched soils
areas of reduced current
isolated from predation by carp or waterfowl (can be achieved through fencing)
9. Project Design
Three different planting methods were examined: crib, fibre pot and free plantings. In 1992, one nearshore enclosure (#1) was planted with equal numbers of all three methods. One offshore enclosure (#2) was planted with all three methods. Two additional offshore enclosures (#3 & 4) were planted with free plants (Figure 1).
10. Implementation
Orange snow fence (0.9 m high) was installed at the site. This installation outlined the work area and offered protection from predation by carp and waterfowl. The fenced area was kept small to inhibit take-off and landings by Canada Geese.
Cedar triangular cribs were built in two sizes. The larger used 1.8 m ¥ 20 cm logs, the smaller used 1.2 m ¥ 20 cm logs. Eight large and seven small cribs were installed within enclosure 1. Large cribs were arranged flush to the fence with small cribs placed between larger ones. T-bars, nails and wire were used to secure cribs to the ground. T-bars were pounded into sediments below water levels. Securing these cribs to the ground proved very difficult. The buoyancy of the cedar material was very high. Eventually, all cribs were submerged.
Cattails, soft-stem bulrush, barberpole sedge, and arrowhead were collected from donor sites within the Metro Toronto vicinity from mid June to late September. Plants were collected by digging "plugs" using shovels. These "plugs" included as much root and associated soils as possible. "Plugs" were placed in fibre pots or large buckets with water for transport.
"Out of ground time" for the transplants was a maximum of 2 h. At Mimico Creek, an area was dug within the cribs or sediments large enough to accommodate the "plug" or fibre pot. The fibre pots were filled with sediment and the pot planted to a depth of 3/4 its height. All species were planted in the same manner.
11. Degree of Environmental Intervention
The areas planted were isolated from predation using snow fence.
This restricted access to these areas by larger fish and waterfowl.
It only slowed/reduced the access of mammals.
12. Cost
4 EYC Crew (8 weeks/yr: 2 years): $20 000
Vehicle & fuel: $2 000
Materials: $3 000
Project management(2 years): $12 000
Monitoring (1wk/yr, 5 years) $6 000
Total Estimated Project cost: $43 000
13. Biological Assessment
An assessment of material survivorship and propagation was completed one year after planting. Frost and ice through the winter of 1992 resulted in lifting the t-bars holding fences and cedar cribs by roughly 1 m above high water levels, and lifted potted materials from the substrates. While the free plants suffered damage due to a harsh winter and high spring water levels, they survived in greater numbers than either other method.
As water levels receded, plant growth increased. As plants broke the water surface they tended to have a silt film covering them. Suspended sediments within the water column may be restricting plant growth potential. Investigation was initiated into the detailed hydrology and sedimentation of the estuary of Mimico Creek and how it may affect the wetland site.
Plants that survived and propagated included cattails (Typha sp.), arrowhead (Sagittaria latifolia) and soft stemmed bulrush (Scirpus validus). There was no sign in 1993 or 1994 of barberpole sedge (Scirpus rubrotinctus). Based on these observations initial wetland plant community establishment has been emphasizing cattail, soft-stemmed bulrush , and arrowhead species.
As a result of isolating planting areas an increase in species, number and vigor of naturally occurring wetland plants occurred. Giant burreed (Sparganium eurycarpon) and arrowhead (Sagittaria latifolia) increased in numbers and size within Enclosure 1 indicating that predation by waterfowl was a factor limiting growth.
Two years after planting, material showed increased propagation. Enclosure areas were more densely established with material expanding beyond the enclosure boundaries. Cattails did not produce seed in 1993 but did in 1994 (Table 1).
Total area of new habitat created is 402 m2.
Table 1. Summary of Wetland Plant Growth (1992-1994): Mimico Creek Wetland Creation Project.
Typha sp. Scirpus sp. Sagittaria sp. Alisma sp. Sparganium sp.
Total Planted 2145 132 62 0 0
Total Grown 2679 372 204 (54) 22 250
% Change 124.9% 281.8% 329% (87%)
14. Measures of Success
Due to a harsh 1992 winter and very high water levels in the spring of 1993, the first years results were disappointing. Evaluation of plant establishment in 1994 showed good survivorship and extensive propagation. The variation in plant community establishment between years one and two shows the need for long term evaluation. Monitoring of this site will continue.
Success Rating: 4 - successful
15. Key References
MTRCA, 1993. Toronto waterfront habitat rehabilitation pilot projects, Technical Report, 1992.
MTRCA, 1994. Toronto waterfront habitat rehabilitation pilot projects, Technical Report, 1993.
Stabb, M., 1988. Wetlands Conservation on a small scale: The beaver baffler and other micro-management projects on private lands. Wetlands: Inertia or Momentum, Conference Proceedings. Federation of Ontario Naturalists, Don Mills, Ontario. pp 94-96.
Correct citation for this contribution:
Vincent, J. 1995. Wetland plantings within the Mimico Creek estuary, Humber Bay park, city of Etobicoke, p. 133-138. In J.R.M. Kelso and J.H. Hartig [editors]. Methods of modifying habitat to benefit the Great Lakes ecosystem. CISTI (Can. Inst. Sci. Tech. Inf.) Occas. Pap. No. 1.