Wetlands &
Watersheds
Browse our research
Tell me about...
wetlands
What is a wetland?
Wetlands are areas that have been soaked by water, such as marshes, swamps, bogs, fens, and seasonally flooded forests. [53] A wetland is home to plants and soils that are adapted to water-logged, saturated conditions. Wetlands help lessen the impact of floods and droughts, absorb pollutants, improve water quality, provide habitats for many species, and protect our shorelines.
Wetlands were once abundant throughout Canada, but now cover only about 13% of the nation’s land area. [54] In southern Ontario, only about 30% of the original wetlands remain. The remaining 70% have been converted from their natural state to support alternative uses, such as agriculture or housing. [55]
Photo credit: Jock Rutherford
Did you know?
…that wetlands are the only ecosystem designated for conservation by international convention? [56]
Wetlands as a
carbon sink
How well soil stores carbon depends on many factors, including soil type, vegetation, and climate. [57]
In general, the colder and wetter, the better! Wetland soils tend to be poor in oxygen, which slows decomposition and lets organic matter build up within them. This means that wetlands are particularly useful for carbon sequestration.
The case of the dissapearing wetlands
A recent study found that 95.5 hectares of wetlands were lost in southern Ontario from 2002 to 2010. [58] Most of those wetlands were under 2 hectares in size. These small wetlands are generally not evaluated or designated as significant enough for protection. The study projected that by 2026, our wetland losses may exceed 400 hectares.
But small wetlands play an outsized role in our ecosystems. They act as stepping stones for species moving between larger wetlands, provide critical habitat for amphibians, water birds, and rare plants, and affect how water interacts with the landscape.
Leaving wetlands intact can not only help the environment, it can also save money, too. Researchers modeled an urban site to simulate a major fall flood, comparing damages under conditions where wetlands were maintained in their natural state and where they were replaced with agricultural land use. [59] They found that if wetlands existed in their natural state, the flood damage costs could have been reduced to $84.5 million, compared to the $135.6 million without the wetlands.
source: mvca.on.ca/lake-huron-shoreline
Wetlands and
climate change
Coastal wetlands, such as those found in along the shores of Lake Huron, “are among the most vulnerable ecosystem types in the Great Lakes.” [60]
A changing climate poses various threats to these delicate areas, including increased surface water temperatures, changing water levels, and increased storm frequency and intensity.
Coastal wetlands provide critical spawning, foraging, and nursery habitat for many species of fish, which are particularly sensitive to both water temperature and dissolved oxygen. [61] Temperature affects how fish grow and reproduce, and oxygen is critical for respiration. Warmer water temperature in wetlands will lead to more rapid decomposition of organic matter. What’s more, the higher the water temperature, the less oxygen can be dissolved in water. Together, these factors have the potential to threaten fish and invertebrate populations, and to lead to dangerously low dissolved oxygen in the water, known as “hypoxia.”
The water levels of Lake Huron are poised to become increasingly variable as the climate changes. Increased water levels can harm aquatic vegetation, while decreased water levels can negatively affect the connectivity between wetlands, tributaries, and the lake, which has impacts on the flow of organic matter. [62] Increased storm surges are likely to bring with them nutrients, sediments, and other contaminants.