Ecology of Tasmania
The biodiversity of Tasmania is of exceptional biological and paleoecological interest. A state of Australia, it is a large South Pacific archipelago of one large main island and a range of smaller islands. The terrain includes a variety of reefs, atolls, many small islands, and a variety of topographical and edaphic regions on the largest island, all of which promote the development of unusually concentrated biodiversity. During long periods geographically and genetically isolated, it is known for its unique flora and fauna. The region's climate is oceanic.
Evolution
The marine fauna of the period, separate from that of the southwest Pacific, was distinguished as the "
This led to long periods of
Flora
The most ancient communities in Tasmania have an ancestry that extend back to a time when the Earth's continents were all joined as single landmass known as
The
Millions of years ago,
Some genera that originated in Antarctic Flora are still a recognised major component of New Caledonia, Tasmania, mainland Australia, Madagascar, India, New Zealand, and southern South America.
There are three species of Nothofagus in Australia. Stands of myrtle beech (
Deciduous beech (Nothofagus gunnii) occurs in mountainous parts of Tasmania. Antarctic beech (Nothofagus moorei) is found in eastern NSW cool temperate rainforests and cloud forests, but does not occur in Victoria or Tasmania.
Australia rafted north and became drier; the humid Antarctic flora retreated to the mainland east coast and Tasmania, while much of the rest of Australian vegetation became dominated by Acacia, Eucalyptus, Casuarina and xeric shrubs and grasses. Humans arrived in Australia 50-60,000 years ago, and used fire to reshape the vegetation of the continent.
The
Investigations of Upper Cretaceous and Early Tertiary sediments of Antarctica yield a rich assemblage of well-preserved fossil dicotyledonous angiosperm wood which provides evidence for the existence, since the Late Cretaceous, of temperate forests similar in composition to those found in present-day southern South America, New Zealand, Australia and Tasmania. It is suggested a paleobotanical habitat similar to the extant cool temperate
Tasmania has
Wet eucalypt forests grow mostly in the south, west and north west, the Tasman Peninsula, and higher altitude areas of north east. Dry eucalypt forests grow where there is little rainfall and droughts are common. Areas such as the east coast, midlands and north east, i.e. the Bass Strait Islands.
Tasmania is home to some of the oldest trees of the world. For example, some individual
The tallest trees in the Southern Hemisphere, and the tallest flowering plants anywhere (99 metres (325 ft) tall or more), are Eucalyptus regnans, Eucalyptus globulus and Eucalyptus viminalis in Tasmania (mostly in the Styx Valley).[4][5][6] Tasmania hosts endemic plant genera as well as plant genera of restricted distribution; an example of such a genus is Archeria.
For millions of years in the past, these types of vegetation present in the island, covered much of the tropics of Earth. The species of Tasmania are relicts of a type of vegetation disappeared, which originally covered much of the mainland of Australia, South America, Antarctica, South Africa, North America[citation needed] and other lands when their climate were more humid and warm. Although humid forests of warmer climates retreated during the glaciations, they re-colonised large areas every time the climate was favourable again. Most of the humid forests are thought to have retreated and advanced during successive geological eras, and their species adapted to warm and wet gradually retreated and advanced, replaced by more cold-tolerant or drought-tolerant sclerophyll plant communities. Many of the then existing species became extinct because they could not cross the barriers posed by new oceans, mountains and deserts, but others found refuge as relict species in coastal areas and Islands.
When the large landmass of the Australian continent developed a drier and harsher climate, this type of forest was reduced to those boundaries areas. Although some remnants of archaic rich flora still persisted in coastal mountains and sheltered sites, their biodiversity were reduced. In times of high sea level such as the present era, Tasmania as an island, has a climate moderated by the Southern and Pacific Oceans and maintained relatively humid and high rainfall, which has allowed these communities to persist to the present day.
The ecological requirements of many of the species, are those of the laurel forest and like most of their counterpart laurifolia in the world, they are vigorous species with a great ability to populate their preferred habitats. The geographical isolation and special edaphic conditions helped to preserve it too.
Many members of the late Cretaceous - early Tertiary Gondwanan flora survived in Tasmania and New Caledonia's equable climate.[7]
Fauna
The invertebrates provide abundant evidence of Gondwanan ancestry. Possibly the best known example is the "mountain shrimp", Anaspides tasmaniae (
The vertebrates with strong Gondwanan affinities include the major family of freshwater fish Galaxiidae, the two families of frogs within Tasmania (Myobatrachidae and Hylidae) and the parrots. Echidnas and platypus evolved from ancient ancestors which inhabited Gondwana too. Close relatives of marsupials thrive in South America and fossil platypus have also been discovered in South America.
The repeated lowering of sea levels during the ice ages of the Pleistocene facilitated the movement of many species more, including the five species of rodent and eight species of bat.
- Thylacine/Tasmanian tiger
The island of Tasmania was home to the thylacine, a marsupial which resembled a wild dog. Known colloquially as the Tasmanian tiger for the distinctive striping across its back, it became extinct in mainland Australia about 4,000 years ago because of competition by the introduced dingo. Owing to persecution by farmers, government-funded bounty hunters and, in the final years, collectors for overseas museums, it appears to have been exterminated in Tasmania.
The thylacine was the largest known carnivorous marsupial of modern times. The thylacine was one of only two marsupials to have a pouch in both sexes (the other is the water opossum). The male thylacine had a pouch that acted as a protective sheath, protecting the male's external reproductive organs while running through thick brush. The last known animal died in captivity in 1936. Many alleged sightings have since been recorded, none of them confirmed. The mature thylacine ranged from 100 to 130 cm (39 to 51 in) long, plus a tail of around 50 to 65 cm (20 to 26 in).[8] The largest measured specimen was 290 cm (9.5 ft) from nose to tail. Adults stood about 60 cm (24 in) at the shoulder and weighed 20 to 30 kg (40 to 70 lb).[8] There was slight sexual dimorphism with the males being larger than females on average.[9]
- Tasmanian devil
The Tasmanian devil is a carnivorous marsupial found on the island of Tasmania. It also occurred on mainland Australia thousands of years ago. The size of a small dog but stocky and muscular, the Tasmanian devil is characterised by black fur with white patches. It has a loud and disturbing screech-like growl, possesses a vicious temperament and is predominantly a scavenger. The Tasmanian devil survived European settlement and was considered widespread and common throughout Tasmania until recently. As with a lot of wildlife, fast vehicles on roads are a problem for Tasmanian devils, which are often killed while feeding on other road-killed animals such as wallabies. They eat everything including bone.
As of 2005, the Tasmanian devil population has been reduced by up to 80% in parts of Tasmania by the devil facial tumour disease, which is gradually spreading throughout the island. It is believed the majority starved when the tumours spread to their mouths, and that the tumours are spread by fighting between devils over carcasses they feed on—typically, fighting devils will bite one another's faces.
There is no known cure for the disease, and intensive research is underway to determine its cause. There is also a captive breeding program being undertaken by the Tasmanian government to establish a disease-free, genetically diverse population of Tasmanian devils outside Tasmania. This has been relatively successful so far.
- Birds
Many birds of the Australian mainland and surrounding oceans are also found in Tasmania. Tasmania has 12 endemic bird species:
- 4 Meliphagidae) – the yellow wattlebird (world's largest honeyeater) and the yellow-throated, black-headed and strong-billed honeyeaters
- 3 Australo-Papuan warblers (family Acanthizidae) – the Tasmanian thornbill, the scrubtit and the Tasmanian scrubwren
- 1 pardalote (family Pardalotidae) – the endangered forty-spotted pardalote
- 1 Australo-Papuan robin (family Petroicidae) – the dusky robin
- 1 cracticine (family black currawong
- 1 parrot (family Psittaculidae) – the green rosella
- 1 rail (family Rallidae) – the Tasmanian nativehen, Australia's only flightless land bird other than the giant ratites (emu and southern cassowary).[citation needed]
The endemic Tasmanian emu was exterminated in the mid-19th century. The Tasmanian wedge-tailed eagle is a threatened endemic subspecies.
- Frogs
Tasmania is home to 11 species of frog. Three of these are found only in Tasmania, the Tasmanian tree frog (Litoria burrowsae), the Tasmanian froglet (Crinia tasmaniensis) and the recently discovered moss froglet (Bryobatrachus nimbus). Of the 11 species that inhabit Tasmania all are endemic to Australia. Tasmania is home to the largest breeding population of growling grass frogs (Litoria raniformis), a vulnerable species, which has declined over much of its range.
- European red fox
On 20 June 2001, Tasmania formed a fox task force, now the Fox Eradication Branch, to eliminate the European red fox. Officials planned to spend up to A$50 million on an eradication campaign, which has since been reduced. No foxes have been captured, poisoned or photographed with certainty in the Island state, although four carcasses have been recovered. Of these, one was claimed to be shot, and the other three presumed road-kills. The lack of an abundance of foxes, through low population densities, and fox-poisoning campaigns, has resulted in an abundance of denial of fox presence by the Tasmanian community. Established foxes in Tasmania could devastate native mammals, livestock, ground-nesting birds and native rodents. Experts estimate there are fewer than 30 million foxes on mainland Australia, having been introduced by European settlers.[10]
Since settlement, about 28 native mammal species or subspecies have become
In addition to the four carcasses, over 40 independently tested fox-DNA-confirmed scats have been located across Tasmania. Through government review, foxes are now confirmed to be in Tasmania.[12] Certain prominent Tasmanians [who?] including Dr David Obendorf have been calling for a Federal Police investigation into allegations that evidence has been planted and this is all part of an elaborate hoax to receive funding from the Commonwealth.[13]
See also
References
- ^ "World Heritage Values – Flora". Parks and Wildlife Service Tasmania. Archived from the original on 28 October 2009. Retrieved 20 February 2010.
- .
- ^ "Native Conifers of Western Tasmania". Department of Primary Industries and Water. 2007-09-20. Retrieved 2008-01-11.
- ^ Mifsud, Brett. "Tasmania's Giant Trees". Retrieved 13 August 2013.
- ^ Mifsud, Brett. "Tallest Eucalyptus". Retrieved 13 August 2013.
- ^ "National Register of Big Trees" (PDF). 2013. Retrieved 13 August 2013.
- ^ "MBG: Diversity, Endemism, and Extinction in the Flora and Vegetation of New Caledonia".
- ^ ISBN 0-7246-6223-5.)
{{cite book}}
: CS1 maint: multiple names: authors list (link - . Retrieved 27 November 2006.
- ^ Mercer, Phil (24 September 2007) 'Fox invasion fear grips Tasmania', BBC NEWS
- ^ Tasmanian Parliament Legislative Council Part 1- Pages 1–61 Hansard 17 April 2007[dead link]
- ^ "Foxes officially confirmed in Tasmania". Australian Broadcasting Corporation. 2009-12-24. Retrieved 2010-04-02.
- ^ "The Federal Police should be asked to investigate". Tasmanian Times. Retrieved 2010-04-02.