The peat swamps on K'gari (also found in Cooloola) are classed as fens, which naturally occur in much cooler climates. These fens are among the oldest in the world, having developed over 6,000 years, and the only known fens found in the sub-tropics. They occur at sea level and merge on the western side of the Island with mangrove forests.

The fens are peat-forming wetlands that obtain nutrients through drainage from upland mineral soils and from groundwater movement from the dunes above. Despite the low nutrient levels, and high acidity, they are able to support diverse animal and plant communities that have adapted to these conditions, such as some frog species, grasses, sedges, rushes, and wildflowers.

More information: Twyford, K. (1996) Fraser's newly discovered fens. MOONBI 89 Newsletter of the Fraser Island Defender's Organisation: Milton, Queensland.