FINAL REPORT - International Joint Commission

ANNEX 2
Context
As in the case of the economic evaluations, the environmental impacts of proposed regulation plans were
measured relative to what is expected to occur if regulation continues in the same manner as it does now,
under the present set of policies.
The focus of the environmental evaluation was on the effect of water levels on coastal marshes. Briefly,
water level regulation has reduced the variety of plant species along the coast, which creates stresses on
animal populations that thrive on plant types that suffer under regulated water levels. In general, a more
diverse environment will better resist impacts from the two greatest environmental threats in the Great
Lakes: toxics and invasive species (Tilman and Downing, 1987; Schindler, 1998). Lake Ontario coastal
marshes provide breeding and feeding grounds for all coastal life, including several species at risk. Water
level patterns have a direct physical influence on the breeding and nesting success of marsh birds and fish.
More varied water levels create more variety in marsh plants, which creates a more productive and robust
coastal ecology and habitat. Water levels below the Moses-Saunders Dam can strand or drown fish and
bird eggs. The societal value of the environment is expressed through laws protecting habitat (i.e., wetlands)
and specific faunal species (special interest or endangered).
The current estimate of coastal wetland area within Lake Ontario and the upper St. Lawrence River is
approximately 26,000 hectares (64,250 acres), made up of four basic types, submerged aquatic vegetation,
emergent marsh, meadow marsh, and upland vegetation (trees/shrubs) (Wilcox, et al., 2005). Over 80%
of the wetland area occurs in the eastern half of the Lake Ontario basin and Thousand Islands region.
Results from study-site analyses indicate a 50% reduction in meadow-marsh and emergent-floating vegetation
since regulation was implemented in the late 1950s. The same period has seen a 29% increase in cattaildominated
emergent marsh area (about 1,700 hectares or 4,200 acres) (Wilcox and Ingram, 2005).
With over 12,000 ha (30,000 acres) of swamps and marshes, Lake Saint-Pierre accounts for 80% of lower
St. Lawrence River wetlands. Lake Saint-Pierre supports a large population of nesting blue heron (more
than 1,300 nests), a major staging area for migratory wildfowl (over 800,000 ducks and geese annually)
and 167 species of nesting birds. Permanently submerged areas, wetlands and the spring floodplain are
home to 13 amphibian and 79 fish species, many of which are exploited by sport and commercial fisheries
alike (Centre St. Laurent, 1996). The ecological value of Lake Saint-Pierre has been recognized by its
designation as a Ramsar wetland, a UNESCO Biosphere Reserve and its inclusion as a protected site under
the Eastern Habitat Joint Venture. The hydrology of the lower St. Lawrence River is much more dynamic
than that of the Lake and upper river throughout each period of the year. It is influenced not only by the
outflows from Lake Ontario, but also by the Ottawa River flow and by the local tributaries. As a result, the
lower St. Lawrence River is less sensitive to regulation.
In addition to impacts caused by regulation, the effects of changes in climate, water temperature, and water
supply can influence the environmental response of habitats and the species they support. Issues such as
invasive species, changes in fisheries management, pollution and population changes, and changes in the
use of the resource can also impact the environment. Regardless of the regulation plan, the environment
will continue to be vulnerable to various stressors such as invasive species, pollution, and land-use
changes. However, the manner in which lake levels are managed can have an impact on the ecological
integrity of the system and its resilience to these other stressors.
20 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows