Sphagnum mosses thrive in wet, acidic, and nutrient-poor environments like peatlands. In good conditions, they grow in dense carpets and can absorb and retain around 20 times their dry weight in water, creating waterlogged, acidic conditions essential for peat accumulation. The moss’s acidic and antimicrobial properties slow decomposition, allowing dead organic matter to accumulate into peat deposits over millennia, which can be several meters thick. Upland and lowland peatlands across the Isle of Man, particularly on moorland hills (e.g. Beinn-y-Phott) and wetlands (e.g. Ballaugh Curragh), have developed peat layers over ~5,000 years under cool, wet conditions.

Sphagnum moss acts as a critical ecosystem engineer in many ways, absorbing water, acidifying its environment, reducing decay, and driving peat formation. It therefore enhances a range of ecosystem services, including carbon sequestration, water management, biodiversity support, and cultural value.

Healthy peatlands are champions of achieving hydrological stability, but only because of the key role Sphagnum moss plays. Sphagnum’s sponge-like retention aids drought, flood and wildfire resilience. It keeps the peatland damp, even during dry spells, maintaining the hydrological balance. It reduces downstream flood risk by increasing surface roughness; helps to maintain a stable water table; and supports drinking water filtration by trapping sediments, including peat. Saturated peat is non-flammable, reducing weather-related, accidental or intentional ignition. Sphagnum helps maintain cooler, humid conditions at ground level, shielding sensitive species from heat stress and insulating the peat, reducing evaporation and drying out.

Healthy sphagnum creates healthy peatlands, which offer crucial habitat for many peatland specialist fauna and flora species, such as carnivorous round-leaved sundews.