Wetland ecotechnology in Canada
Wetland ecotechnology can be subdivided into three broad categories. Habitat wetlands are used to offset losses of natural wetland habitat. Ducks Unlimited Canada, who is celebrating their 60th anniversary in Canada this year, has been designing and constructing habitat wetlands for decades with much success. Their activities have contributed to conservation and wise-use of wetlands on the major migratory flyways in regions of Canada, such as the Prairies (Murkin 1989) or Little Clay Belt in northern Ontario (Fig. 1), that otherwise would lack wetlands mainly due to agricultural drainage and encroachment. Ducks Unlimited has accumulated much valuable expertise and unique designs for earth dykes, fishways, concrete structures, steel piling controls and dykes that is of value to the wetland ecological engineering community as a whole.

Treatment wetlands are used to improve water quality (Figs. 2 and 3). Treatment wetlands, are a "low-tech" above ground alternative to traditional water treatment technologies. They are affordable and require little maintenance (e.g. Brix 1993; Jewell 1994; Kadlec and Knight 1996; Hammer 1997). Canadians have experimented with the use of both surface flow and subsurface flow treatment wetlands since at least the 1970s with growing success. Many early systems, thought to be failures, were probably not real failures at all but simply represent early engineering proto-types and ecological experiments that were probably in need of further refinements and modification in design and use before being abandonned. Harsh growing conditions and winter climate are generally thought to interfere with effective year-round operation, thereby making wetlands unrealistic treatment options. Early research results from Canada and abroad, however, indicate that winter operation should no longer be a major concern (e.g. Smith et al. 1997). The Listowel, Ontario experiment was initiated in 1979 (Wile et al. 1985) and another experiment was underway around the same time at Humboldt, Saskatchewan (Lakshman 1979). These projects represent brave and visionary experiments that resulted in a large volume of data being collected and much being learned about treatment wetland technology. Other successful projects incorporate some combinations of pond, holding tank, filtration unit (sand, peat or other material), and wetland for polishing secondary and tertiary wastewater. The New Hamburg treatment plant in Ontario is an example of a full-scale system that is one of the longest operating and was the first in the country to combine a sand filter and a wetland for treating municipal wastewater (B. Gross, personal communication). Every province and territory in Canada has or has had a treatment wetland system for domestic, municipal, or industrial wastewater (i.e. Pries 1994; Berezowsky 1995).

It is also possible to combine wetland ecotechnologies to serve multiple purposes. Ducks Unlimited is exploring the possibilities of combining habitat and treatment wetland technologies. An example is the River Hebert Marsh in Nova Scotia (Fig. 4; McCullough 1996). Tertiary wastewater from two aerated municipal sewage treatment lagoon cells flows into a 2 ha surface flow treatment wetland. A diversity of aquatic plants, invertebrates, insects and birds occupy the wetland habitat. A similar project exists at the Shand Power Station near Estevan, Saskatchewan (B. Duncan, personal communication).

Erosion and flood control wetlands provide protection from flooding and erosion. While dykes, reinforced rock walls, weirs, or other structures are constructed to minimize erosion and flooding and protect adjacent lands from damage, in many cases wetlands are created in the newly protected areas. Numerous examples exist along both marine coasts of Canada and along the shores of many lakes. Some sites such as Oak Hammock Marsh on Lake Manitoba and the Lake St. Clair Wildlife Area on Lake St. Clair are recognized as wetlands of international importance.

The need for the amalgamation of science and engineering
Basic principles of ecological engineering were introduced on the national lecture tour followed by a cook's tour of natural wetland systems in Canada, where differences between bogs, fens, swamps, marshes, and shallow waters were described, to illustrate the diversity and complexity of wetlands in Canada. There are about 100 different natural wetland types in Canada (Warner and Rubec 1997). There has not been any attempt to classify the wide range of engineered wetland types in Canada, but 20 to 30 is probably a conservative estimate. The self-design and sustainability of sound ecologically engineered wetlands depends on a thorough understanding of the ecological processes supporting wetland systems. Wetland ecotechnology is still very much at an experimental phase. Although there are many examples where treatment wetlands are meeting or exceeding expectations, many designs are based more on trial and error than on science. Little scientific data exists in Canada on how these wetlands function and so this has led, in some instances, to inefficient systems that were in need of latter refinements. Moving wetland ecotechnology from being an art to being a science is one of the most immediate challenges. This will require engineers and ecologists to work closely together. There is a need to establish well-instrumented demonstration sites of various kinds supported by long-term performance evaluations in representative geographic regions of Canada. In order to promote this emerging technology at the municipal level, a five-step technology development process has been proposed (Li et al. 1997); such a process could be easily adapted to either larger scale or single sites:

• Physical constraints and suitability (e.g., soil type, water source, space requirement, liability) of the technology should be determined.
• Practical design criteria and methodology should be developed.
• Construction techniques and materials should be identified.
• Comprehensive evaluation of performance should be conducted through rigorous field monitoring programs.
• Operational and maintenance requirements should be defined for municipal and private operators.

We know that habitat wetlands do create habitat and that treatment wetland do treat wastewater, but until it can be demonstrated why and how, wetland ecotechnology will probably neither gain widespread acceptance nor attain its full potential. Habitat wetlands might be considered more straightforward to design than treatment wetlands, and certainly it seems reasonable to expect that technological combinations for more than one purpose make good engineering, ecological and economic sense. Treatment wetlands pose some of the biggest challenges. Perhaps the easiest place to start is to use wetlands for sewage treatment or other wastewater rich in organics or other chemicals that can easily break down by the wetland process. Let us understand fully how these wetlands perform with these simpler wastes and let us get some good designs in place, before blindly extending treatment wetlands to the full range of wastewaters that contain the more toxic and persistent chemicals. Such an approach is responsible and may allay concerns, for example, of many wildlife biologists who generally regard all treatment wetlands as having negative impacts on wildlife (Wren et al. 1997; Cole 1998; Murkin 1998). Certainly the most hazardous of chemicals do potentially pose the biggest threats, but this is almost certainly not the case with all wastes in all kinds of treatment wetlands. It should be noted that wetland soil biogeochemical processes and wetland plant physiologies have built in mechanisms that operate against bioaccumulation in sediment or in plant tissues and are equipped to break down some toxic substances into gases for release to the atmosphere. What these processes are, how they relate to the various kinds of wastewaters, and what the linkages are between chemicals in wetland wastewaters and wildlife diet remain are poorly understood. Some of the concerns expressed by wildlife biologists revolve around storm water ponds, which in many cases and in strict terms, are neither habitat wetlands nor treatment wetlands. Clearly, the challenge in wetland engineering is to design treatment wetlands that do not pose threats to either wildlife or humans.

Ecological engineering should not be used as the excuse to destroy natural wetlands. Instead, it offers the opportunity to augment the overall extent of existing wetland. Furthermore, we believe it is too early to consider using natural wetlands for wastewater treatment. Based on our current poor understanding of the processes regulating many natural wetlands and on the treatment processes in treatment wetlands, let us avoid possible complications with natural systems. The surface and ground water flow systems in natural wetlands are open and not closed and cannot be controlled as they could be in engineered systems.

Future Challenge
Wetland ecotechnology is: (a) a low "tech", low cost, low maintenance and aesthetically appealing alternative to conventional technologies, (b) interdisciplinary in nature that requires scientists (e.g. biologists) and engineers to work together, (c) in need of science to understand how and why such wetland systems work, (d) in need of continued experimentation to develop new and improved wetland plans and designs, (e) in need of demonstration sites for education and research purposes, (f) in need of a comprehensive technology development process to promote its implementation at the municipal level. Until designs can be tested and supported by science, the immense market opportunities for a wide-range of applications of wetland ecotechnology will not be fully realized.

The engineering and scientific communities must be willing to work with governments and regulatory agencies to develop mutually expeditious procedures for approval. Wetlands in general, and wetland ecotechnology specifically, are dynamic systems that change as they age. As best as we know at this stage, most well-designed engineered wetlands improve with age and the reverse is often true only if there are some oversights in the design or in the selection of the construction site. As difficult as it may be engineers and scientists will have to develop procedures, such as codes or manuals of best practices as reference for regulators.

Many engineers seem hesitant to accept wetland ecotechnology because it lacks the traditional elements of engineered systems and such systems may be difficult to control and predict (Cole 1998). Additionally, engineers are legally responsible for their design. Thus, it takes time to educate the engineering profession to accept an untraditional technology. Regulators also have similar difficulties because policies and guidelines are either absent or in development. Clearly there will be a need to develop provincial and national guidelines on the creation and use of wetlands in environmental management. Interdisciplinary working groups should be established to take on the task of formulating such guidelines as is being undertaken in the US (Cole 1998). Technology transfer is also important in promoting this technology to engineering and environmental professionals. We should try to educate ourselves through conferences, workshop, seminars, and Internet web sites. It is clear that there is great potential for engineered wetlands across the country. Canadians do have experience and expertise. We need to share our knowledge, and learn and work together.

Acknowledgements
This paper highlights some information gathered while Warner was the 1998 National Lecturer on behalf of the Hydrotechnical Division of the Canadian Society for Civil Engineering. We wish to thank J. Anderson, Golder Associates Ltd., and local hosts for organizing the various lectures. The tour greatly benefited from the involvement of Ducks Unlimited Canada. R. Coley, Ducks Unlimited Canada kindly critiqued a draft of this paper.

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