Section 4.4
Status of Wetland-associated Mosses
Summary of the effects of human disturbance on moss species associated with wetlands in the boreal forest as measured by the Biodiversity Intactness Index.
Updated January 2025
The average intactness of wetland-associated mosses in the forested region was 94%. Intactness by wetland category was:
Bogs & Poor Fens
98%
intact
Rich Fens
96%
intact
Swamps & Marshes
92%
intact
Generalists
.jpg)
90%
intact
This section was updated in January 2025 to reflect additional moss data, updated species models, and new human footprint results. The number of moss species reported on increased from 45 to 56. Overall, habitat suitability for most wetland-associated moss species remained largely unchanged.
Introduction
Mosses—technically classified as bryophytes, a group that includes mosses, liverworts, and hornworts—are among the most important indicators used to classify certain wetland types, playing a key role in defining their ecological characteristics, functions, and overall condition[1,2].
- In peat-forming wetlands, such as bogs and fens, mosses often dominate the ground cover and play a vital role in ecosystem processes. They are essential to organic matter accumulation (commonly known as peat), while also influencing nutrient cycling, water retention, decomposition, and acidification, all of which contribute to the distinct characteristics of these ecosystems[3].
- In swamps and marshes, the moss layer is typically less developed but remains ecologically important[4,5]. Mosses in these wetlands provide critical habitat for microorganisms and contribute to essential functions such as nitrogen fixation. Wet depressions within swamps, in particular, serve as rich habitats for diverse moss species, including leafy mosses such as Rhizomnium and Plagiomnium species, as well as spear mosses like Calliergon species.
- Due to their sensitivity to variations in water levels and chemical composition (e.g., nutrients, pH), individual moss species are valuable indicators for identifying microhabitats within different wetland types[1]. For example, Warnstorf’s Peat Moss (Sphagnum warnstorfii) thrives in nutrient-rich fens with a pH range of 5 to 7, and is typically found in lawns and low hummocks. Meanwhile, Marsh Leafy Moss (Plagiomnium ellipticum) commonly grows in wet depressions within wooded fens and forested swamps.
Warnstorf’s Peat Moss (Sphagnum warnstorfii)
Marsh Leafy Moss (Plagiomnium ellipticum)
In this section, we report on the status of wetland-associated moss species classified into four wetland types (bogs & nutrient-poor fens, rich fens, swamps & marshes, generalists) in the forested region of Alberta, using the Biodiversity Intactness Index. These results have been updated incorporating more data, updated species models, and human footprint as of 2021.
Foundation of Peatland Ecosystems
Mosses are keystone species of peatland ecosystems.
- Peatlands are wetlands where plant production is greater than decomposition, resulting in an accumulation of peat (partially decomposed plant material).
- Peatlands are the dominant category of wetland in Alberta, comprising 90% of our wetlands.
- Peatlands exist along a continuum from bogs that are acidic and nutrient poor, typically dominated by Sphagnum mosses, to rich fens that are neutral to alkaline and nutrient rich. Fens are characterized by different moss species depending on their nutrient status; poor fens feature Sphagnum species, while rich fens are dominated by brown mosses.
- Peatland communities occur along a gradient from hummocks (elevated mounds) to hollows (flatter and wetter habitat). The height of hummocks can range from a few centimetres to a metre.
- Peatlands are sensitive to changes in water chemistry, hydrology, and climate, making moss species good indicators of ecosystem health.
Intactness for moss species associated with wetlands. This graph shows the predicted deviation in species abundance from intact reference conditions (100%) for moss species associated with four wetland types: bogs/poor fens, rich fens, swamps/marshes, and generalists. Solid line indicates no change in habitat suitability between the current landscape with human footprint and the modelled reference landscape without human footprint. Both positive (predicted increases) and negative (predicted decreases) deviations from reference result in lower intactness. Each dot represents an individual species; hover over a dot to view individual species intactness values.
