Peat moss (Sphagnum) is a non-vascular plant that forms the foundation of peatlands. Peat is the partially decayed organic matter that accumulates over millennia when plant production exceeds decomposition. These peatlands, often called mires, bogs, or fens, cover vast areas globally and function as significant carbon sinks.
Global Geographic Distribution
Sphagnum-dominated peatlands are heavily concentrated in the Northern Hemisphere’s cooler climates, particularly across the boreal and subarctic regions. These high-latitude areas, characterized by cool temperatures and high moisture, provide the ideal macro-climate for peat accumulation.
Major countries hosting these vast peat resources include Russia (possessing one of the largest peatland areas globally) and Canada, particularly in the Hudson Bay Lowland and the Mackenzie River Valley. Extensive peatlands are also found throughout Scandinavia (Norway, Sweden, Finland), Northern Europe, and the northern United States, notably Alaska. While the Northern Hemisphere holds the majority, smaller peat areas exist in the Southern Hemisphere, including parts of southern Chile and Argentina (Magellanic moorland), New Zealand, and Tasmania.
Essential Environmental Conditions
Peat moss growth is dictated by environmental conditions that slow decomposition and promote organic matter accumulation. A consistently high water table is necessary, keeping the soil fully saturated and creating anaerobic conditions. This state severely limits the oxygen needed for microbial and fungal activity, the primary drivers of decay, thus preserving the plant material.
The water chemistry is highly acidic, typically featuring a pH range between 3.0 and 4.5. Peat moss actively contributes to this acidity by releasing hydrogen ions. This low pH further inhibits decomposition, as most decomposer microbes cannot function efficiently. Peatlands also feature extremely low nutrient availability, known as oligotrophic conditions. The water source is often solely precipitation, which is inherently low in dissolved minerals. This combination of saturation, acidity, and nutrient scarcity creates a specialized habitat where Sphagnum outcompetes most other plants.
Classification of Peatland Habitats
Peat moss grows in two main types of peatlands, bogs and fens, distinguished by their water source. These classifications are based on the habitat’s isolation from mineral-rich groundwater, which determines nutrient level and acidity. Sphagnum moss dominates both types, but its role and the surrounding plant communities differ.
Bogs
Bogs are ombrotrophic peatlands, receiving all water and nutrients exclusively from atmospheric precipitation. This isolation from mineral soil results in a highly acidic and nutrient-poor environment. Sphagnum moss is the primary vegetation component, forming dense, spongy carpets. The moss’s ability to maintain these acidic conditions makes the bog a habitat for specialized, acid-tolerant flora.
Fens
Fens are minerotrophic peatlands, receiving water from precipitation and from groundwater or surface runoff that has passed over mineral soil. This external water supplies dissolved minerals, resulting in higher nutrient content and a less acidic (often slightly alkaline or neutral) pH compared to bogs. Fens support a greater diversity of plant life, including sedges and other mosses, alongside Sphagnum. Poor fens are an intermediate stage, often more acidic than rich fens and dominated by Sphagnum, indicating a transition toward the more isolated bog condition.