Section 2.3
Wetlands in the Prairie Region
Summary of the area of wetlands in the prairie region by wetland class with a description of the most common classes.
Total area of wetlands in the prairie region: 6.9%
- Marsh is the most common wetland class, covering 4.4% of the prairie region, followed by open water (1.9%) and swamp (0.6%).
- The area of wetlands in protected areas in the prairie region is low at 2.8%.
Introduction
Wetlands in the prairie region tend to be small but numerous and are mainly made up of marshes and shallow open water wetlands, like ponds and sloughs.
Also known as prairie potholes, these depressional wetlands were left behind by retreating glaciers thousands of years ago.
While wetlands cover a small area of the prairie region, they serve a number of important functions:
These boreal wetland ecosystems are important for a number of reasons:
- Wetlands in the prairie region are incredibly productive environments rich in biodiversity that support large and complex food chains and provide essential habitat for wildlife.
- Part of the "duck factory" of North America, these wetlands are a globally significant breeding and migratory stopover area for waterfowl, shorebirds, and landbirds.
- Wetlands stabilize water supplies and reduce the negative effects of floods and droughts.
- Wetland vegetation and soil act as a filter purifying the water before it recharges local water tables.
Wetlands in the prairie region have been impacted by human development activities:
These boreal wetland ecosystems are important for a number of reasons:
- In the last century, the estimated loss of wetlands across the Canadian prairies is 40–70%[1].
- Historically, wetlands were commonly drained and filled to cultivate fields; wetland losses continue as a result of human development including urban expansion, intensification of agricultural practices, and energy development.
- Water quality in wetlands can also be affected by surface run-off from land uses such as agriculture and urban development.
In this section, we summarize wetland class and percent area covering the prairie region in Alberta. We also highlight key wetland characteristics and species associated with the most common wetland classes.
Methods
- The prairie region wetland inventory includes the Grassland and Parkland natural regions of Alberta, excluding the Peace River Parkland Natural Subregion.
- Wetland locations were delineated using open source data and machine learning. Four classes of wetlands were identified (bog, fen, marsh, and swamp) plus open water habitat. The open water habitat category includes shallow open water wetlands—i.e., areas that are less than two metres deep—but also includes open water areas, like lakes, that are deeper than two metres. Upland areas were also identified.
- Steps to identify and classify wetlands in the forested region of Alberta are listed below. For detailed methods see ABMI 2021[2].
- Protected areas are defined as provincial protected areas (a list of the eight categories can be found here) and national parks.
Steps to identify and classify wetlands in the prairie region:
- Open data sources of satellite imagery and a digital surface model (DSM) were used as computer inputs.
- First, the hydroperiod (the length of time and portion of the year the wetland holds water) across the area was calculated. Spring, summer, and fall optical images were segmented into similar areas using computer scripting. The segments were labeled as flooded or non-flooded by an interpreter. These labeled segments were fed back into the computer to label the rest of the segments.
- To differentiate open water areas from seasonally varying wetlands (flooded potholes), the fall segments were overlaid onto the spring. Open water was assigned to segments that stayed flooded while the flooded potholes were dry in the fall.
- To assign a wetland class, a trained photo interpreter labeled the wetland class for 2,900 of these previously created segments to generate known wetland locations. Using the computer inputs, the computer “learned” the characteristics associated with each wetland type, such as topographic position and vegetation properties, based on known wetland locations.
- Based on these characteristics for each wetland class, the computer created rules that were used to identify other possible wetland locations in the prairie region. These rules were applied across the prairie region to create an inventory of wetlands.
- Before finalizing the prairie wetland inventory, areas with steeper slopes were considered to not be wetlands and were masked out. Finally, the inventory was reviewed at a 1:33,367 scale to fix obvious errors such as missing lakes.
Limitations and constraints:
- The Parkland and Grassland Wetland Inventory (prairie region) is based on open source satellite imagery of 10-m2 spatial resolution from the years 2017–2020, with a specialized methodology designed to identify wetlands that were seasonally flooded during that time period.
- The prairie product approaches a 400 m2 Minimum Mapping Unit, but some potholes between 400 m2 and 800 m2 are missed. Users should be aware there are many smaller wetlands in southern Alberta that could not be captured in this inventory. In addition, linear riverine wetlands could not always be captured by this method.
- The Parkland/Grassland Wetland Inventory classification has an overall accuracy of 90% compared to photo-interpreted validation data. Since by far the majority of the wetlands in the prairies are either marsh or swamp, there are fewer wetland classes to be confused in this region. The most common confusion or error in this inventory is between upland vs. swamp or marsh, especially confusion between upland vegetation and shrubs in the Parkland region and swamps. Refer to the technical documentation for more details on class accuracies.
Amelia Martin
Hydroperiod was calculated to differentiate open water areas from seasonally flooded potholes.
Results
Area of Wetlands in the Prairie Region
Total area of wetlands in the prairie region: 6.9%
Highlights
- Wetlands cover 6.9% of the prairie region.
- Marshes are the most common wetland class, covering 4.4% of the prairie region, followed by open water (1.9%) and swamps (0.6%).
- The area of wetlands in protected areas in the prairie region is low at 2.8% (300 km2 out of 10,720 km2)
- The area of each wetland type represented in protected areas is low, with similar areas for open water (2.6%) and marshes (2.7%); representation of swamps in protected areas is higher, at 3.4%.
Distribution of wetlands in the prairie region of Alberta. Click on the legend to turn wetland types on and off. Note: wetlands cover less area than what is displayed in the map.
More about wetlands
Click on a tab for a description of the most common wetlands in the prairie region. For more detailed descriptions of each wetland class, refer to the Alberta Wetland Classification System Field Guide[3].
About marshes in the prairie region
- Marsh is the most common wetland class, covering 4.4% of the prairie region.
- Marshes have a variety of water inputs such as rain or snowmelt; surface water flowing from adjacent lakes, rivers, and creeks; and groundwater.
- Water levels can fluctuate with some marshes only temporarily flooded or covered by standing or slow-moving water much of the time[3].
- Marsh boundaries may not be as well-defined as those of other waterbodies such as ponds, and these areas may dry out by the end of the summer.
- Marsh soils are rich in nutrients; marshes are characterized by a variety of water-tolerant grasses and sedges as well as emergent vegetation like cattails and rushes.