As much as 80% of the shoreline has been artificially hardened (e.g. large stones, concrete, metal retaining walls, etc.). This negatively affects habitat for fish and other aquatic species, as well as other wildlife such as birds, butterflies and turtles.
Urban development affects the quality and amount of natural space close to the shoreline.
Overfishing, trampling, and picking native plants are just a few examples of activities that degrade these natural spaces as viable habitats for plant, animal and fish species.
The Credit River is the second-largest single source of phosphorous to Lake Ontario on the Canadian side. Phosphorous is a key factor in the growth of algae along the waterfront.
Other pollutants that make their way from the nearby urban and rural communities include nitrogen, ammonia, heavy metals, suspended solids and chlorides.
Urbanization has effects on the flow of streams and groundwater. As surfaces are paved or built upon, the amount and velocity of water runoff directly into streams, creeks and rivers increases on rainy days, and more pollution is washed directly into waterways and into the lake.
Lake Ontario water levels are artificially manipulated for navigation and hydroelectricity by large dams and as a result of human water use. These changes can have negative impacts on natural habitats such as coastal wetlands.
Climate change is affecting lake levels through evaporation and other processes, and this in turn affects the overall health of the aquatic and terrestrial habitat found along the shoreline. A decrease in shoreline ice cover means winter storms may have greater adverse impacts.
Invasive species dominate Lake Ontario’s aquatic ecosystem and are a significant problem in and near the lake. Invasive species are difficult to manage because they tend to be resilient, spread aggressively, and outcompete native species for habitat and nutrient sources. Examples of invasive species include: English ivy, periwinkle, round gobies, quagga mussels and common carp.