Funding source: Burnett Mary Regional Group

Identified scientifically less than two decades ago, the unique patterned fens of southeast Queensland’s Great Sandy Region continue to fascinate conservation researchers.

Fens are grassy wetlands occurring along large lakes and rivers. The patterning of their vegetation and the fauna they sustain indicate the kind of environmental conditions which shaped their formation, such as wind direction and surface run-off.

Twenty fen complexes covering 521 hectares have been discovered in the Great Sandy Region: the northernmost at Wathumba on Fraser Island; and the most southerly near Lake Cooloola.

A UQ research team, along with colleagues from other Australian and international universities, is studying these natural phenomena, the only subtropical patterned fens in the world.

What they learn will influence regional conservation decisions in the future, and possibly resolve debates about human settlement of Australia some 40,000 years ago.

Unlike Northern Hemisphere patterned fens which formed lakes as vegetation grew over several millennia, Queensland’s patterned fens gradually filled in lake systems with flora that thrived in the highly acidic and anaerobic groundwater. These plants, such as the spreading rope rush (Empodisma minus), helped produce the combinations of pools and ridges (string-flarks) and strings and ridges (string-mires) that distinguish fens from other wetland systems.

Patterned fens represent a unique opportunity to examine past environmental change and human impact. Their peat bases of partially decayed vegetation from the past several thousand years are rich botanical and fire archives. Sediments from the Great Sandy Region, for example, indicate the previous existence of wetlands that were highly resilient to burning patterns and periods of climate change.

The fens are now home to many rare or threatened frog and fish species. They provide habitat for distinctive native birds and several species of migratory birds.

But the fens are also threatened by sea-level rise, either through direct flooding or by altering the underlying freshwater lens and impacting the groundwater feeding them.

The research focus has turned to the potential reasons for this alteration, and investigating other patterned fen sites formed in response to potential threats like altered burning regimes. Analysis of fossil pollen and charcoal fragments has revealed how these ecosystems probably responded, providing critical data for informing future conservation planning.