Peat mounds of southwest Tasmania: palaeoecological insights into their origins, age and significance for biological conservation

Peat mounds have been shown to play a critical role in climate regulation, biodiversity conservation, and water management in the Northern Hemisphere, though little is known about the role of similar features in the Southern Hemisphere. In Tasmania between 41^o-43.5^o south latitude, the growth of blanket bogs occurs as a result of a combination of cool, wet climate and fire, extending from sea-level up to the regional tree line at 700–900 m and covering some 10 000 km² of hilly to mountainous terrain. These blanket bogs are among the most extensive in the southern hemisphere and are considered to be of major international conservation significance. A rare but significant feature of the blanket bog system is the appearance of circular peat mounds which rise up to 3m above the blanket peats and are confined to elevations within 100 m of sea level in flat valley floors of southwest Tasmania. These peat mounds are rare in the Australian landscape and are considered to play a significant role in the long-term sustainability of local endangered flora and fauna, particularly the Orange-bellied Parrot, of which there are less than 100 individuals remaining in the wild today relying on the food sources provided by vegetation growing on the peat mounds.

We describe the origin, age and palaeoecology of peat mounds on the Melaleuca Plains, adjacent to Bathurst Harbour, in the Tasmanian Wilderness World Heritage Area. Using pollen and charcoal analysis alongside radiocarbon dating of a set of cores taken from two peat mounds and one local lagoon, we reconstruct regional to local vegetation change and fire history to determine the extent and veracity of landscape degradation imposed by the removal of long-term Indigenous land management around 200 years ago after the onset of British colonisation. Our results map out the pace and nature of ecosystem change during the Holocene and show that recent increases in fire activity and ecosystem degradation poses serious environmental risks to the long-term survival of the Orange-bellied Parrot, and the peat mound landscape as a whole. A better understanding of decadal to centennial scale environmental dynamics of peat mounds has the potential to assist in preserving these critical ecosystems worldwide.