Location and General Description
Western Tasmania is the coolest and wettest region of Australia, with some areas receiving up to 3600 mm of rainfall per annum. The climate is temperate and maritime, with mild winters and cool summers when compared with other regions at similar latitudes. Snow, frost, and fog are common (Harris et al. 1995). Rainfall is heaviest in winter, but in general, is not strongly seasonal (Willams 1974). Substrate here consists largely of hard, slow-weathering Precambrian quartzose rocks (Jackson 1999a). The western region of Tasmania has a rugged topography, with a chain of north-south mountains that were formed as the quartzose basement sediments were folded repeatedly. Unlike mainland Australia, large areas of western Tasmania were glaciated repeatedly over the past 2 million years, and this region bears the unmistakable imprint of glaciers. Ranges are dotted with cirques, arêtes, and U-shaped valleys, with widespread morainal material and deepened lakes (Jackson 1999b).
Rainforest can be found at a range of elevations, from sea level up to sub-alpine habitat. Rainforest at higher elevations is dominated by Nothofagus spp. Lowland rainforests are also dominated by Nothofagus spp., with species of Atherosperma, Eucryphia, Phyllocladus, and Andopetalum increasing in frequency as soil quality decreases. Rainforest vegetation shows greater diversity and complexity on low nutrient soils, so that vegetation on high-fertility soils is structurally and floristically simple in comparison (Jackson 1999a). Distinctive rainforest species include Australia’s only winter-deciduous tree, Nothofagus gunnii, as well as myrtle beech (Nothofagus cunninghamii), sassafras (Atherosperma moschatum), King Billy pine (Athrotaxis selaginoides), pencil pine (Athrotaxis cupressoides), horizontal (Anodopetalum biglandulosum), Huon pine (Lagarostrobus franklinii), celery-top pine (Phyllocladus asplenifolius), and chestnut pine (Diselma archeri). Rainforest vegetation is extremely sensitive to fire, so that where fire frequency is increased, old, mature eucalypts stand over a tall understory of Acacia spp. and mesophyll species of Olearia, Bedfordia, Pomaderris, and Phebalium (Jackson 1999a). A variety of other communities occur here, including wet sclerophyll forest, buttongrass moorlands, alpine vegetation, scrub, and heath (Bryant and Jackson 1999).
Tasmania’s environment is thought similar to that once found on Gondwana. The temperate rainforest shows affinities to the present day flora of New Zealand and South America. Species of Nothofagus, Pseudopanax, Caltha, Aristotelia, Coprosma, and Orities demonstrate Tasmania’s Gondwanan heritage (Read 1999). Tasmania is the only place in the Southern Hemisphere that has plants from the family Taxodiaceae, including the King Billy pine, the pencil pine, and the long-lived huon pine. The huon pine can achieve ages greater than 2,000 years, making it one of the longest-living organisms on Earth (Parks and Wildlife Service Tasmania 1999). Although species diversity among vascular plants is low in rainforest, endemism is high. Formerly glaciated regions are especially likely to hold endemics because the diversity in soil types and the migration of species provided ample opportunity for speciation, microevolution, and hybridization (Jackson 1999b). Nearly half of Tasmania’s 600 species of lichens occur in rainforest, mostly as epiphytes. The Tasmanian Wilderness World Heritage Site occupies the southern portions of this ecoregion and comprises over 700 vascular plants, of which 240 are endemic (representing two-thirds of Tasmania’s endemic higher plant taxa) (Harris et al. 1995). This ecoregion also contains large areas of wet schlerophyll forest, and contain the greatest diversity of living plants and animals in Tasmania. These forests are noted for their high biomass production on relatively infertile soils, and for a dominant species, the swamp gum (Eucalyptus regnans), which is the tallest flowering plant in the world, growing over 100 m in height (Johnson 1998).
A number of species are restricted to this ecoregion, including the critically endangered orange-bellied parrot (Neophema chrysogaster) (Hilton-Taylor 2000), which returns from its wintering range on mainland Australia to breed in coastal southwest Tasmania. The birds utilize a wide variety of habitat, nesting in tree hollows only on the edge of rainforest and eucalypt forest, and feeding in buttongrass plains. Whereas flocks numbering in the thousands were recorded in the 1800s, less than 200 of these birds remain today (Bryant and Jackson 1999). Twenty-one species of native birds regularly utilize rainforest habitat, including the grey goshawk (Accipiter novaehollandiae), brown scrubwren (Sericornis humilis), and black currawong (Strepera fulignosa). Mammals found in the rainforest include the dusky antechinus (Antechinus swainsonii) and the spotted-tail quoll (Dasyurus maculatus) (VU) (Hilton-Taylor 2000), as well as several Tasmanian endemics, including the Tasmanian long-tailed mouse (Pseudomys higginsi), Tasmanian pademelon (Thylogale billardierii), and Tasmanian devil (Sarcophilus harrisii) (Wildlife Service of Tasmania 2000). The Tasmanian pademelon was once found on mainland Australia but was eradicated due to loss of habitat and overhunting for meat and pelts (Strahan 1998). The monotypic amphibian Bryobatrachus nimbus is found only in the southern, lowland moist forests of this ecoregion. One reptile is endemic to this ecoregion, the Pedra Branca skink (Niveoscinus palfreymani), which can be found only on tiny, offshore Pedra Branca Island and is considered vulnerable (Hilton-Taylor 2000). The invertebrate fauna found in rainforest includes a number of ancient and primitive species, such as the giant velvet worm (Tasmanipatus barretti), northwest velvet worm (Ooperipatellus cryptus), and Hickman’s mountain shrimp (Allanaspides hickmani).
A large portion of this ecoregion is protected by the 13,800 km2 Tasmanian Wilderness World Heritage Site. Less than 25 percent of the Tasmanian Wilderness World Heritage Site contains rainforest vegetation, which can grow only where fires are infrequent (Harris et al. 1995). In general, rainforest vegetation is well-conserved, with 45 percent found in protected areas and another 12 percent currently proposed for protection (Brown and Podger 1999). Out of an identified 38 communities, all but six are deemed to have good representation in protected areas (Jarman et al. 1991 in Brown and Podger 1999). Wet eucalypt forest are not as well-represented in protected areas, with only 18 percent of this community included in reserves (Brown and Podger 1999).
Types and Severity of Threats
The forests of this ecoregion have considerable economic value: native conifers such as King Billy pine and Huon pine as well as some eucalypts are valued for their timber; the leatherwood tree is a nectar source for valuable honey; and the Wilderness Area draws large numbers of tourists. Logging, mining, and off-road vehicle recreation are all threats outside the World Heritage Site and fire is the biggest threat throughout the region. Fires eliminate rainforest, replacing it with mixed forest and scrub. There has been a 32 percent loss of King Billy pine forest over the last 100 years (Harris et al. 1995), and any fire event is likely to cause a local extinction of King Billy pine, Huon pine, and Nothofagus gunnii. Other threats to this ecoregion are inappropriate increase in tourist frequency and use in protected areas and the spread of Phytophthora cinnamomi, a root-rotting fungus that attacks a range of native plants. Although still a threat, introduced predators are not nearly as problematic as they are on the Australian mainland.
Justification of Ecoregion Delineation
The Tasmanian Temperate Rainforest ecoregion includes the majority of three IBRA’s: all of ‘D’Entrecasteaux’ and ‘West and South West’, and most of ‘Woolnorth’, except for King Island (Thackway and Cresswell 1995). This ecoregion encompasses most of the ‘Western Tasmanian Wilderness’ Centre of Plant Diversity (Harris et al. 1995).
Brown, M.J. and F.D. Podger. 1999. Conservation of Tasmania’s Natural Vegetation. Pages 381 – 400 in J.B. Reid, R. S. Hill, M. J. Brown, and M. J. Hovendon, editors. Vegatation of Tasmania. Flora of Australia Supplementary Series. No. 8. Australian Biological Resources Study, Environment Australia, Canberra.
Bryant, S. and J. Jackson. 1999. Tasmania’s Threatened Fauna Handbook: what, where, and how to protect Tasmania’s threatened animals. Threatened Species Unit, Parks and Wildlife Service, Hobart, Tasmania.
Jackson, W.D. 1999a. Vegetation Types. Pages 1-10 in J.B. Reid, R.S. Hill, M.J. Brown, and M.J. Hovendon, editors. Vegatation of Tasmania. Flora of Australia Supplementary Series. No. 8. Australian Biological Resources Study, Environment Australia, Canberra.
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Jarman, S.J.,G. Kantvilas, M.J. Brown. 1999. Floristic and ecological studies in Tasmanian rainforest. Tasmanian Forest Research Council Research Report No. 2, Hobart, Tasmania, Australia.
Johnson, S. 1998. Tasmanian Wilderness World Heritage Area: flora. http://www.parks.tas.gov.au/wha/vegetati/veg.html. Viewed on August 17, 2001.
Harris, S., J. Balmer, and J. Whinam. 1995. Western Tasmanian Wilderness. Pages 495 – 499 in S. D. Davis, V.H. Heywood and A.C. Hamilton. editors. Centres of Plant Diversity. Volume 2. Asia, Australasia, and the Pacific. WWF/IUCN, IUCN Publications Unit, Cambridge, UK.
Hilton-Taylor, C. 2000. 1998. The IUCN 2000 Red List of Threatened Species. IUCN, Gland, Switzerland and Cambridge, United Kingdom.
Parks and Wildlife Service Tasmania. 2000. Rainforest of Tasmania. http://www.parks.tas.gov.au/veg/rainfor.html. Viewed on August 20, 2001.
Parks and Wildlife Service Tasmania. 1999. Native Conifers of Tasmania. http://www.parks.tas.gov.au/veg/pines.html. Viewed on August 17, 2001.
Read, J. 1999. Rainforest ecology. Pages 160 – 197 in J.B. Reid, R. S. Hill, M. J. Brown, and M. J. Hovendon, editors. Vegatation of Tasmania. Flora of Australia Supplementary Series. No. 8. Australian Biological Resources Study, Environment Australia, Canberra.
Strahan, R. 1998. The Mammals of Australia. Australian Museum/Reed New Holland. Sydney, Australia.
Thackway, R. and I.D. Cresswell. editors. 1995. An Interim Biogeographic Regionalisation for Australia: a framework for establishing the national system of reserves, Version 4.0. Australian Nature Conservation Agency, Canberra.
Williams, W.D. 1974. Introduction. Pages 3 – 15 in W.D. Willams. editor. Biogeography and Ecology in Tasmania. Mongraphiae Biologicae, Volume 25. Dr. W. Junk, The Hague.
Prepared by: Miranda Mockrin
Reviewed by: Roger Kitching