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The sustainability of Sphagnum moss harvesting in Australia

Abstract of a report written by Dr Jennie Whinam
Tasmanian Parks & Wildlife Service for Environment Australia, June 1997

Background

Sphagnum peatlands make up only a small fraction of the landscape of south-eastern Australia, but they are a distinctive and unique habitat.

Sphagnum moss is extensively used by the horticultural industry. Its water holding capacity makes it a useful potting medium, particularly favoured by orchid growers and for wrapping rose and fruit tree rootstock for transportation. At present all Sphagnum harvesting in Australia is from natural (i.e. wild) populations. S. cristatum is the most common species in Australia, and is the main species harvested, although S. australe and S. subsecundum are often harvested as well.

Sphagnum peatlands generally form in situations of relatively high rainfall and low evaporation, in areas never or rarely subject to drought, between 300 and 1500 m elevation and in infertile, anaerobic soils. The most common settings for Sphagnum peatlands are in river valleys, beside lakes and streams or on sandstone shelves, where drainage is impeded. The acid environment created by Sphagnum deters bacteria and fungi which would otherwise decompose the dead material. This allows peat to accumulate.

The long-term viability of Sphagnum harvesting is influenced by altitude, shade, watertable level and the retention of moss cover over a peatland. Sphagnum moss growth rates appear to be relatively slow in Australia, as most peatlands occur in the montane and sub-alpine zone, with very few sites appearing viable for sustainable Sphagnum moss harvesting.

To assess the sustainability of harvesting, several sites were selected in Tasmanian and Victorian Sphagnum peatlands in different environments and harvesting conditions to measure the growth of Sphagnum moss. S. cristatum was the species measured at all sites. The growth rate varied in Tasmania from 0.4 cm/year at a high altitude site (950 m) at Mt Field to 4.2 cm/year at an extremely sheltered, highly productive site at 530 m in central Tasmania. In Victoria, the growth rate at the high altitude (1380 m) site at Baw Baw varied from 1.9 cm/year to 5.2 cm/year at a sheltered site at 900 m in the Central Highlands. Not surprisingly, moss growth declines as altitude increases.

CODE OF PRACTICE FOR Sphagnum MOSS HARVESTING

Harvesting

Sphagnum moss harvesting should be excluded from :

1. Alpine and sub-alpine sites (i.e. sites with a minimum mean January temperature of 10 degrees Celsius or less).
2. Sites that :
* are on basalt;
* are on limestone (in sinkholes);
* contain rare or threatened plant/animal species or communities;
* are floating (i.e. aquatic) moss beds;
* rainforest-Sphagnum peatlands;
* that are undisturbed sites.
3. Small Sphagnum peatlands (sites less than 20 ha).
4. Sites with a fluctuating watertable.

Management Prescriptions

Where harvesting occurs, the impacts on harvesting on a site can be minimised by :

1. Retaining shrubs during harvesting.
2. Retaining approximately 30% Sphagnum moss cover and spreading it on any bare patches that occur during harvesting.
3. Avoiding the use of machinery that cuts up bog surfaces.
4. Leaving an even surface so that all remaining Sphagnum is close to the watertable.
5. Allowing in the order of 5-10 years regeneration before reharvesting.
6. Minimise roading and drainage works in the catchment above and surrounding Sphagnum peatlands.

Reservation Prescriptions

Reserves of Sphagnum peatlands should be :

1. of adequate size and number to allow for natural changes and to conserve different types
2. prioritised to target reservation of undisturbed sites.

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