Around the world, the main threats to biodiversity that are a result of human activities can be summarized by the following categories:
Threats to biodiversity interact to have a cumulative impact on the health of the environment and the species that live there. For example, the loss of wetlands and vegetation along watercourses increases the amount of pollution that reaches the aquatic environment and the amount of sun rays on the water’s surface. Pollution and rising water temperatures can limit the health and survival of some native species that are not adapted to these conditions and can make them more susceptible to disease. Invasive species can often live in degraded environments and reproduce at higher rates increasing their spread, which further threatens native species as they are outcompeted for food and habitat. Overharvesting, illegal poaching, trade or commercialization of native species are examples of human disturbance and overexploitation that are added stressors and contribute to populations becoming unstable.
Treasures of the Sydenham
The Round Hickorynut is an endangered mussel species that has been lost from 90% of its Canadian Range – it is now only found in the East Sydenham River and St. Clair River Delta. The largest threats to this species are pollution and siltation. The invasion of the Zebra Mussel that was introduced to Lake St. Clair in the mid-1980s has also contributed to the loss of this species from its former range. Threats to one of its host fish species, the Eastern Sand Darter (another Species at Risk), also threatens the Round Hickorynut.
In the Sydenham, the most significant threats to biodiversity that also have the greatest chance of improvement fall under the categories for habitat loss and pollution. The biggest threats to aquatic life in the watershed are sediment loads, excess nutrients, toxic chemicals, temperature changes, and invasive species.
Together, forest and wetlands makeup less than 15% of the land use in the watershed. There is less than half of the forest cover and only a tenth of the wetland cover considered the minimum needed to sustain a healthy environment. The natural areas that exist in the Sydenham are a refuge for native plants and animals, including species at risk.
A particular issue in the watershed is the continued loss of natural areas and vegetation along watercourses – these areas provide important habitat, shade the water, and reduce the amount of pollution that enters the aquatic environment. In areas lacking riparian vegetation, pollution in the form of soil, excess nutrients like fertilizers and manure, and toxic compounds like herbicides and pesticides are washed off the land into watercourses during rain events or periods of snow melt.
Algal blooms are evidence that excess nutrients are entering the aquatic environment.
Vegetated buffers along watercourses are important for bank stability as well as capturing nutrients and soil in runoff. The roots of living plants anchor the soil in place.
Maintaining and restoring vegetation along watercourses is essential to reduce the amount of pollution that reaches the aquatic environment, it also helps to reduce flooding downstream, and provides habitat for plants and animals.
An added benefit of maintaining a vegetated or grassed riparian buffer along municipal drains is it reduces the need for drain maintenance as the soils are kept on land.
Overland runoff is a major route for soils and excess nutrients to enter the aquatic environment. Bare soils can also be eroded by the wind.
Using best management practices like grassed waterways and cover crops help to reduce the exposure of bare soil to the elements, preventing them from ending up in the surrounding watercourses. Not only is this loss of valuable topsoil bad for crops, it is also bad for the aquatic environment.
The Sydenham River supports a warm water biological community but further increases in water temperatures adds stress to the survival of most species. One impact is that as water temperatures increase, the dissolved oxygen levels aquatic animals need to respire decreases.
Both the loss of riparian vegetation and presence of reservoirs increase the amount of water that is exposed to the sun’s rays, which leads to rising water temperatures. Climate change is another factor that is increasing average air and water temperatures.
Effects of Climate Change
Climate change is resulting in warmer average annual temperatures, more extreme weather events, and periods of flood and drought. Not only does this result in stress and mortality for plants and animals, these are large scale impacts that are a concern for the health and safety of people.
During periods of drought, the water levels in the river can become very low, exposing areas of river bottom and stranding animals like mussels that are unable to move large distances.
Restoring natural features like forests, wetlands, and riparian vegetation are vital to mitigating the impacts of climate change.
An example of human disturbance in the Sydenham is people driving motorized vehicles like ATVs through the river. This crushes the animals that live in the water and destroys their habitat.
Non-native species like Round Goby, Common Carp, and Phragmites are invading the Sydenham watershed. They can directly or indirectly impact native species and their habitat.
The Round Goby is an invasive fish species that is spreading through the Sydenham watershed, it directly and indirectly threatens the survival of native aquatic species.
Round Goby directly impact native fish by eating their eggs and outcompeting them for food and habitat. They also directly affect mussel populations by consuming juvenile mussels and are a sink for glochidia. Since freshwater mussels rely on native fish species to act as hosts for their larvae to complete their life cycle, native fish being displaced by gobies reduces the reproductive success of native mussels. So when Round Goby directly impact the fish community in the Sydenham, they are also indirectly impacting the native freshwater mussel community.
The Common Carp is an invasive species found throughout the Sydenham watershed, it is a bottom-dwelling fish that uproots aquatic plants which increases turbidity. They also feed on animals that live in the sediment, including juvenile mussels.
Phragmites australis is a tall reed grass from Eurasia that once introduced in an area can quickly dominate the vegetation communities and form dense stands that are impenetrable to wildlife. This cuts wildlife off from habitat that they would previously use to breed, forage, or hibernate. “Phrag” (as it is often called) spreads by both seeds and rhizomes. It is also allelopathic, meaning its roots release chemicals into the soil that prevents the growth of other plant species.
Invasive species management
There are many different organizations in the watershed and surrounding region working together to remove Phrag and control its spread.
You can learn more about Invasive Phragmites and Ontario’s invasive species at www.invadingspecies.com
In order to understand and track the health of the watershed, biologists monitor fish, mussel and benthic communities, collect water quality samples, and deploy temperature gauges. This information helps to understand the health of the watershed, determine what is threatening it, and where resources should be directed to improve it.
The health of the watershed relies on the good practices of community members and landowners. There are many partners working together to reduce these threats and restore the natural ecosystem functions. Learn more about what you can do to be a good steward of the environment by visiting our page on how to Get Involved!
© 2026 · St. Clair Region Conservation Authority - The Sydenham River Watershed
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