Western Australia occupies nearly one third of the Australian continent. Due to the size and the isolation of the state, considerable emphasis has been made of these features; it is the second largest administrative territory in the world, after Yakutia in Russia, despite the fact that Australia is only the sixth largest country in the world by area, and no other regional administrative jurisdiction in the world occupies such a high percentage of a continental land mass.
Its capital city, Perth, is also considered to be amongst the world's most isolated, being closer to Jakarta in Indonesia, than to the Australian national capital in Canberra.
Introduction
Western Australia's geology has components that are considered some of the oldest and most recent. The oldest minerals of the world have been discovered at the Jack Hills, and the Yilgarn craton of the Great Western Plateau, which occupies most of the state, has been above sea level for over 2.5 billion years, giving it some of the oldest soils on the planet.
The European settlement of Western Australia started in 1826, at Albany, but the state was only established as an administrative colony in 1829, and much of the state was only subsequently developed, with the extent of the pastoral industries from the 1860s and with the mineral industries from the 1890s to the present day. Western Australia has the highest proportion of non-state born population of any of the Australian states, and this coupled with the fact that over 76% of the population live in Perth means that the proportion of the population who have a deep understanding of the geography of their state is limited.
The geography of Western Australia has been of interest ever since the 17th century when the state was first visited by Dutch East India Company (VOC) explorers, traveling the shorter "Roaring Forties" route from Cape Town to Batavia (Jakarta) in what was then the Dutch East Indies (now Indonesia). Lacking the ability to accurately measure longitude, it was easy to overestimate the distance required to be traveled with the consequence that arrival upon the western shores of Western Australia became a more frequent occurrence.
Dutch explorers too often suffered from collision with the many reefs along the western coast, a result of the warm Leeuwin current, that baths the western shores, and has a huge effect upon creating the favourable Mediterranean climate of the south west corner of the state. Abel Janzoon Tasman, for instance, was sent from Batavia to scout the size of the new continent discovered. By the mid 18th century, the whole of the Western shoreline of the state had been mapped to a reasonable degree of accuracy, although these maps were improved subsequently by the British explorers George Vancouver, Phillip Parker King and Matthew Flinders.
Climate
Western Australia is divided in half climatically by a belt of descending dry high pressure system airflow, generally along the Tropic of Capricorn between the north, in which a summer rainfall pattern predominates, and the south, characterised by winter rainfall.
The northern part of the state, characterised by Monsoonal circulation, in the winter months from May to September is of generally warm dry offshore winds, drawn across the Inter-Tropical Convergence Zone by the low pressure systems of Monsoon Asia. In summer, from November to March, with the displacement of the Intertropical Convergence over northern Australia, the weather is characterised by humid tropical onshore airflows, coupled with thunderstorms and an occasional cyclone, these weather patterns bringing the bulk of the rainfall of the region. The highest wind-gust recorded on the Australian mainland was 259 km/h at Mardi during tropical cyclone Trixie, in 1975 and Whim Creek has the record for the highest rainfall, at 747 mm in 24 hours, associated with a cyclone in 1898.Australian Bureau of Statistics "Western Australian Year Book, 1997"
In the southern part of the state the bulk of rainfall comes from west to east moving cold frontal low pressure depressions, originating off the edge of the winter pack-ice in the Southern Ocean, south of South Africa. Cold southern airflows, wedging beneath humid north westerly winds triggers vertical instabilities, bringing this region the bulk of its rain between May and August. During the summer months these frontal depressions travel well to the south, leading to warm high pressure systems dominating the southern part of the state.
As a result, the state is classified with five climates in the Köppen climate classifications, ranging from Aw Tropical wet-dry climates in the Kimberley region of the state, through BSh Semiarid (summer rainfall) to the south of the Kimberley, BW Arid climates, covering the Great Sandy Desert, Central Australian Desert, Gibson Desert and the Great Victoria Desert, BSh Semiarid (winter rainfall), from Shark Bay to the Nullarbor, and then a Csa Mediterranean climate from Northampton to Esperance and covering the Southwest of the state.
Kimberley region Between April and October the climate is characterised by dry months with clear blue skies, moderate daytime temperatures and cool nights. The "wet season" however, is hot and humid with monsoonal winds bringing consistent and sometimes torrential rain. Broome, (with a rainfall of 513 mm in 47 days) for instance has had 356 mm of rain in 24 hours. Cyclones forming off the coast, in the 1970s formed only twice a year and crossed the coast only every second year, although with global warming this frequency is increasing. The torrential rain swells the rivers through run-off, and the resulting floods in dry river beds can lead to loss of livestock, property damage and occasionally loss of life. Communities may be cut off through road flood damage. Prior to being dammed, the Ord River delivered more than 50 million litres a second, past Wyndham (652 mm in 56 days) into the Cambridge Gulf.
Central and Goldfields region This is a region of salt-lakes, sand-dune rides, and is covered with desert oaks and mulgas. Laverton for instance has an average rainfall of only 192 mm over 41 days in average, although this rainfall is extremely erratic, and the area can go without rainfall for nearly a year, and then receive the equivalent of its annual rainfall in only a few hours. Close to the centre of the Western Australian border Giles Meteorological Station records only 219 mm of rain over an average of 43 days. Whilst Laverton receives the bulk of its rain from frontal systems that occasionally extend through to the Goldfields, Giles is generally dry from July through to September and gets the bulk of its rain from tropical cyclones which collapse into tropical depressions, bringing sudden rain into the interior.
Gascoyne and Pilbara region This semiarid region lies astride the summer and winter rainfall regimes. In the north Dampier, for instance, with 402 mm of rain over 23 days has its wettest months in January, February and March, whilst Carnarvon with 239 mm of rainfall over 45 days, peaking June and July. Like in the Kimberley, this region is characterised by an extreme tidal range, leaving the coast surrounded by mangroves and mudflats, which, again like the Kimberley, in earlier years were important as a source of wild pearls and oysters. Inland the river gorges are inclined to flash flooding with the occasional sudden downpours, giving sufficient water for sheep and cattle stations.
Southwest region This region has cool wet winters, and hot dry summers, with rainfall decreasing and summer temperatures increasing with distance from the sea. The region ranges from Pemberton, located in the Karri Forest region of the extreme southwest corner of the state has an average rainfall of 1244 mm over 167 days, to Bencubbin in the northeast wheat belt with only 319 mm over 73 days. Coastal regions are generally free from frosts, although frost conditions on winter nights are not uncommon. The state is generally snow free throughout winter, although an occasional fall is reported once or twice a year on the Stirlings or Porongurups north of Albany (837 mm over 179 days). Snowfalls have been recorded as far north as Wongan Hills, and as late in the year as November. Perth is supposedly the second windiest city in the British Commonwealth (after Wellington, New Zealand), and it is not uncommon in winter to have wind-gusts of up to 135 km/h. Forested areas generally have the highest rainfall, and there is a marked rain shadow effect along the Darling Scarp, with the result that the rainfall pattern shows an area of higher rainfalls extending from Collie north to the Chittering Brook and Karnet.Rainfall figures from "Western Australia: an atlas of human endeavour 1829-1979" (Western Australian Government Press)
Depletion of stratospheric ozone The southern half of Western Australia is greatly affected by the depletion of atmospheric ozone. While the rate of increase in the size of the ozone hole is slowing, 2006 figures produced by NASA show that the size of the hole that year was the biggest on record, averaging 27.4 million square kilometers in extent. As a result, the figures that suggest that 1/3 of Western Australians will in the course of their life suffer from skin cancers, has caused a huge change in popular behavior. From being a part of a nation of sun-loving beach-goers, Western Australians have adopted a habit of "slipping" on a shirt, "slopping" on a 15+ sunscreen and "slapping" on a hat. Unfortunately the effects of the ozone hole on Western Australian livestock, or on our native flora and fauna is much less understood. The increase in numbers of blind kangaroo suffering from ultraviolet caused cataracts has been recorded in local newspapers, but the overall effects has not been studied.Department of Environment and Conservation (2007)"State of the Environment Report"
Climate change and global warming The International Panel on Climate Change has shown that the natural ecosystems can absorb approximately two tonnes of carbon dioxide per person per year.Stern, N. (2006). "Stern Review on The Economics of Climate Change (pre-publication edition). Executive Summary". HM Treasury, London. Archived from the original on 31 January 2010. Retrieved 31 January 2010. At the moment the world, through the burning of fossil fuels and the clearing of forests is emitting 6.8 tonnes of carbon dioxide per person per year,Source: Houghton, R.A., 2003. Revised estimates of the annual net flux of carbon to the atmosphere from changes in land use and land management 1850-2000 with the result that over the last century the concentration of carbon dioxide has gone from 280 parts per million to 380 parts per million, a change equivalent to that seen since the depths of the last Ice Age. While in Europe the average rate of emissions is currently about 10 tonnes per person, and the average in the US is over 20 tonnes, for Australia as a whole produces about 26 tonnes of greenhouse gas emissions per person. (current Australian figures accepted by the Western Australian government). 2003 data listing CO2 emissions only are listed at List of countries by carbon dioxide emissions per capita.
Western Australia emits 33.1 tonnes of net carbon dioxide equivalents (CO2-e) per capita, State of the Environment Report for Western Australia (July 2007). making the state one of the highest contributors per capita in the world.
Examples
Biogeography