In contrast with mainland Australia, Tasmania Wilderness is rugged and forested; it is also scenically spectacular. The Tasmanian Wilderness World Heritage Area (WHA) is geologically and geomorphologically complex and the product of at least three major glaciations. The western half of the island is underlain by fold structures, the eastern half by fault structures, both of which are represented in the World Heritage Area. The fold structure region in the southwest is extremely craggy and densely vegetated, with north-south oriented mountain ranges and valleys. The rocks vary in age from Precambrian to Devonian and were subjected to two major orogenies, the Frenchman and Tabberaberan. Precambrian formations are widespread and consist of quartzite, schist, phyllite, conglomerate, dolomite, siltstone and sandstone. The more resistant sequences such as quartzite and quartz schist form most of the prominent ranges; the less resistant schists, dolomite and phyllite underlie many of the valleys and plains.
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| Tasmanian Wilderness |
Faulting in the east and north produced the distinct scarp-bounded plateaux and residual hills that contrast dramatically with the fold structure province to the south. This region includes the Cradle Mountain-Lake St Clair National Park, Walls of Jerusalem National Park, parts of Lemonthyme and Southern forests and the Mount Anne and Mount Ronald Cross areas. It includes a plateau of sedimentary roof-rocks in the Walls of Walls of Jerusalem National Park and Central Plateau area with a myriad of small lakes, and Lake St Clair which is the deepest lake in Australia. The rocks are Permian-Triassic sediments capped by Jurassic dolerite, and generally occur above about 600m, except in the east. Basement rocks, probably of Precambrian, Cambrian, Ordovician and Silurian age, are generally overlain by upper and lower horizontal sediments of the Parmeener Supergroup.
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| Walls of Jerusalem National Park and Central Plateau |
The Permian lower unit consists of glacio-marine sequences including tillite, sandstone, siltstone, mudstone and limestone horizons. The upper Triassic unit contains banks of sandstone, mudstone, siltstone and coal, probably laid down during a humid, cool climate in swamps, lakes and river channels. These rocks contain rare plant and amphibian fossils. A dramatic period of igneous activity followed the deposition of these sediments in the Jurassic, with the injection of massive amounts of dolerite into the sediments. Owing to its resistant nature the dolerite still covers a vast tract of the World Heritage Area.
Below about 600m, depositional features are typical, including moraines and other outwash deposits. Periglacial activities, including much slope instability, caused gelifluctate, landslip and talus deposits. The river drainage system has a pronounced trellis pattern, with only the larger rivers, notably the Franklin and Gordon rivers, having cut directly through the mountain ranges, producing spectacular gorges. The lakes of the Denison Range are of great interest because of their physical and chemical characteristics. An analysis of the chemical properties, light regime and the Tasmanian endemic algal flora shows that the lakes are indicators of the east-west divide.
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| Franklin and Gordon rivers |
Lake George and later Lake Pedder in the meadows of the Gordon River valley were created by the Hydro-Electric Commission in the early 1970s. The coastline experienced a number of sea-level changes during the glaciations. It is now a classic example of a drowned landscape, seen in the discordant coastline in the south, and the rias at Port Davey and Bathurst Harbour. The geological variety underlies a corresponding diversity of soil and vegetation types, including extensive peatlands (Nomination document, 1988).
CLIMATE
Tasmania has a temperate maritime climate, wet, windy, cloudy and cool. The south-west in the westerly airstream of the Roaring Forties is the wettest region in Australia. Rainfall over the Gordon-Franklin basin ranges from about 1,800mm in the headwaters of the Franklin to over 3,400mm near Serpentine Dam. The east is far drier (Bosworth, 1977). Average annual temperatures range between the low teens in winter and the low twenties in summer.
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| Freycinet Peninsula |
FAUNA
The fauna is of world importance because, protected by isolation, it includes an unusually high proportion of endemic species and ancient relict groups. In invertebrate groups for instance endemism ranges from 20% to 100%. The varied topography, geology, soils and vegetation together with the harsh and variable climatic conditions have combined to create a wide array of habitats and a correspondingly diversely adapted fauna: the scrubland, heath and moorland animals have many unusual adaptations. The insularity of Tasmania and of the southwest wilderness has protected them from the impacts of the exotic species that have seriously affected the mainland fauna. Two main faunal groups co-exist there: one that includes the marsupials and burrowing freshwater crayfish that are relicts of the Gondwanan fauna; the second, including rodents and bats, that invaded Australia from Asia millions of years after the break-up of Gondwanaland. The invertebrate fauna, including cave-adapted species, is outstanding: many are ancient relict species such as the velvet worms Euperipatoides and Ooperipatellus spp. which have changed little in the last half billion years. They are considered a missing link between the annelids (worms) and the arthropods (crustaceans and insects) (Nomination document, 1988).
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| Cradle Mountain |
Of Tasmania's 32 mammal species, 27 are present in the area. Four of these are endemic to Tasmania including Tasmanian devil Sarcophilus harrisii, the world's largest extant carnivorous marsupial, the eastern quoll or ‘native cat’ Dasyurus viverrinus, Tasmanian pademelon or rufus wallaby Thylogale billardierii and the rodent-like Tasmanian betong Bettongia gaimondi. The Tasmanian wolf Thylacinus cynocephalus (EX) was last seen in 1936. 13 of the 150 bird species recorded are endemic, including the iconic orange-bellied parrot Neophema chrysogaster (CR: 200 individuals), one of Australia's rarest and most threatened birds, found in the far southwest (Brown et al., 1985). There are 11 reptile species, of which four are endemic and of six frog species two are endemic. The moss froglet Bryobatrachus nimbus is a recently discovered species. The Tasmanian tree frog Litoria burrowsi is mainly restricted to the area. There are 15 species of freshwater fish including four endemic species. Two native fish, Lake Pedder galaxias Galaxias pedderensis (CR) and swamp galaxias G. parvus are largely restricted to the area. In 2003, 28 vertebrate and 3 invertebrate species were listed as nationally endangered (PWS, 2004).
Within aquatic habitats, the freshwater crustaceans are of global significance, as are many amphipods, isopods, crayfish and shrimps which are relictual Gondwanan fauna. Three lakes on the Lower Gordon River are of international repute for being permanently stratified (meromictic) yet relatively shallow and inhabited by diverse and unusual aquatic micro-organisms. Streams, rivers, coastal lagoons and estuaries support many species of native fish such as the swan, barred and clarence galaxias Galaxius fontanus (CR), G. fuscus (CR) and G. johnstoni (CR), western paraglaxias G. occidentalis, Australian grayling Prototroctes maraena (VU) and a highly endemic aquatic invertebrate fauna. However, introduced species, such as brown trout Salmo trutta and eastern brook trout Salvelinus fontinalis have contributed to the decline of several native species of fish. Major rivers, such as the Old and Davey rivers in the south-west and New River in the Southern Forests, are of importance for scientific reference because of their pristine state. Many of the 175 Tasmanian invertebrates listed as rare or threatened are protected within the WHA. These include such species as freshwater snails, caddisflies, stoneflies and dragonflies.
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| Southwest National Park |
VISITORS AND TOURIST FACILITIES
At least half a million tourists a year visit the WHA and visitor numbers between 1992 and 1999 increased from ±400,000 to ±550,000 (PWS,2004). Visiting is markedly seasonal, peaking in January and low during winter and spring. Most tourists are day visitors and follow a similar circuit route around Tasmania, visiting Cradle Mountain, Strahan and Lake St Clair. The most popular single site in the area is Cradle Mountain which received 200,700 visits in 1999-2000, a substantial increase over the approximate 80,000 annual visits of the late 1980s. In 1997 the Gordon River received at least 105,000 visitors per annum and in 1999-2000 Lake St Claire received about 104,000. Other popular access routes include the Lyell Highway, and the Strathgordon and Scotts Peak roads into the centre of the Area.
There are now four Visitor Centres, at Lake St Clair, Cradle Mountain, Strachan and Mt. Field and a museum in Cradle Mountain Park. The site provides a range of recreational and wilderness activities, including bushwalking, fishing, boating and canoeing, riding, licensed hunting (of wallabys), camping, caving, mountaineering, climbing, rafting, and cross-country skiing. Long-established trails such as the Overland Track and South Coast Track provide high quality wilderness walks (PWS, in litt.,1996). The Area is well publicised and the tourism and tourist developments are well monitored. Commercialised tourism, in cooperation with the Parks Service, is on the increase. A tourist lodge on Pumphouse Point on Lake St Clair may be developed.
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