Australian Peatlands

by Elizabeth Bilney

Peatlands are a distinctive wetland type which, though common in some parts of the world, are rare in Australia.

The largest and best example of an upland peatland in Australia is the Wingecarribee Swamp, lying in the gently sloping upper catchment valley of the Wingecarribee River in the southern highlands of New South Wales. Peat formation began here some 14 700 years ago and averaged around 24 centimetres each 100 years, but this rate of accumulation has slowed considerably. The peatbeds of the swamp are between 3 and 6 metres deep and hold within them a record of past climates and vegetation types, species and changes, providing a major storehouse of natural history records.

The swamp provides the only known habitat for one of the world's largest dragonflies (Petalura gigantea), which grows up to 20 centimetres in length. The family to which the genus Petalura belongs, dates back to the Jurassic period, and there are only nine species worldwide, with four being endemic to Australia. Of great scientific interest is the dragonfly's life cycle, with the larvae surviving in the swamp and peat from six to thirty years, spending the daytime in their mud burrows and emerging at night to feed on the surface of the swamp.

The swamp also supports a large and diverse range of plant species, including sedgelands, rushlands, reedbeds, aquatic herbfields, mossbeds and tussock grasslands, which in turn provide a range of habitats for many native birds, animals, reptiles and insects.

As with all peatlands, Wingecarribee Swamp plays a major role in the control of water flow to the downstream river system, and in the filtering of nutrients and pollutants.

Unfortunately this valuable resource is under threat, as peat mining for horticultural purposes continues in the Wingecarribee Swamp. In other countries where peat bogs are widespread, peat has been mined for generations as a source of fuel. In Australia, where these bogs are rare, any peat mining can threaten the ecological character of the wetland. Peatlands are also particularly vulnerable to fire, which has increased in frequency since European settlement. Burning and trampling by stock has in some cases led to the total destruction of vegetation and drying up of the peat, followed by considerable erosion of the surrounding land.

There are other peatlands in New South Wales which include small peat deposits in the Monaro Region, at Barrington Tops and in the New England area. The Australian Alps also contain a significant range of fens, bogs, and peatlands. Relatively undisturbed areas of upland peatland occur at Rennex Gap, near Jindabyne, and Tomneys Plain near Tumbarumba. Tomneys Plain, which sits in a large valley meandering through relatively undisturbed forest, consists of well developed Sphagnum hummocks with underlying bog peats about 3 metres in depth. Also significant are the Mount Buffalo Peatlands, which encompass Bunyip Bog and Crystal Bog.

Peat is generally found on plains in high valleys where topography results in slower drainage. Substantial peat deposits take thousands of years to form, and the organic material does not break down completely. Peatlands therefore have high research value as their sediments act as repositories of valuable information about ecosystem history and local environmental changes. Subalpine peatbogs, such as these, prove to be particularly informative recorders of vegetational change. They are located between montane and alpine zones, whose boundaries and component flora may have altered significantly over time.

Although peatlands occur on all continents and are estimated to cover 500 million hectares of land surface, they include very distinct and complex ecosystems. Because peat has been discovered to be of great use to humans (for both fuel and horticultural purposes), the ecological character of peatlands faces a threat not shared by all wetlands. We are, however, learning that peatlands are of immense value to us in other ways; historical, scientific and ecological.

Elizabeth Bilney, Australian Peatlands, Wetlands Australia, no. 6, July 1997, pp. 6-7.