Southwest Australia
Southwest Australia is a biogeographic region in Western Australia. It includes the Mediterranean-climate area of southwestern Australia, which is home to a diverse and distinctive flora and fauna.
The region is also known as the Southwest Australia Global Diversity Hotspot.[1][2][3][4]
Geography
The region includes the Mediterranean forests, woodlands, and scrub ecoregions of Western Australia. The region covers 356,717 km2, consisting of a broad coastal plain 20-120 kilometres wide, transitioning to gently undulating uplands made up of weathered granite, gneiss and laterite. Bluff Knoll in the Stirling Range is the highest peak in the region, at 1,099 metres (3,606 ft) elevation.[citation needed]
Desert and xeric shrublands lie to the north and east across the centre of Australia, separating Southwest Australia from the other Mediterranean and humid-climate regions of the continent.[citation needed]
Climate
The region has a wet-winter, dry-summer Mediterranean climate, one of five such regions in the world. During the winter months, westerly winds bring cool weather, clouds, and rainfall to Southwest Australia. In the summer months, the lower-latitude anticyclonic belt, with generally dry easterly winds, moves southwards, increasing temperatures and decreasing rainfall. Tropical cyclones, off the shore of northern Western Australia during the December-to-March northern wet season, occasionally reach as far south as Perth before moving inland, bringing floods and damaging winds to the west coast and rain to the dry interior.[5]
Rainfall generally decreases from south to north, and with distance from the coast. The highest rainfall is typically in the Karri Forest Region between Pemberton and Walpole, up to 1,400 mm (55 inches) annually.[5]
The region has been experiencing the effects of human induced climate change. Average annual rainfall has declined as much as 20% since the 1970s, declining by 10-20 millimetres each decade. Summertime maximum temperatures have increased by 0.1º to 0.3º C per decade, and the average number of days per year over 40º C in Perth has doubled over the last century.[6] Lower rainfall and higher temperatures have reduced stream flow and inflow into drinking water and irrigation catchments since the 1960s. The summer of 2021/22 was the hottest on record.[citation needed]
Flora
Southwest Australia is recognised as a
Vegetation in the region is mainly woody, including
Southwest Australia is home to many endemic
Fauna
The honey possum (Tarsipes rostratus) is a tiny marsupial endemic to Southwest Australia that feeds on nectar and pollen, and is an important pollinator for several southwestern plants including Banksia attenuata, Banksia coccinea, and Adenanthos cuneatus. Other mammals endemic to Southwest Australia are the western brush wallaby (Macropus irma) and the quokka (Setonix brachyurus).[citation needed]
Southwest Australia is an
Ecoregions
The World Wide Fund for Nature and Interim Biogeographic Regionalisation for Australia (IBRA) divide the region into six ecoregions and ten biogeographic regions:
- Coolgardie woodlands (IBRA Coolgardie and Hampton)
- Esperance mallee (IBRA Esperance Plains and Mallee)
- Jarrah-Karri forest and shrublands (IBRA Warren)
- Southwest Australia savanna (IBRA Geraldton Sandplains, Avon Wheatbelt, and Yalgoo)
- Southwest Australia woodlands (IBRA Jarrah Forest)
- Swan Coastal Plain scrub and woodlands (IBRA Swan Coastal Plain)
The transitional Coolgardie, Hampton, and Yalgoo bioregions are generally drier than the rest of the Southwest. They considered part of Southwest Australia by the WWF, but are considered part of the Central Australian or
Freshwater
Southwest Australia has several permanent rivers and streams, including the
Arid regions separate Southwest Australia's freshwater habitats from Australia's other year-round rivers. As with its terrestrial flora, Southwest Australia's Mediterranean climate and biogeographic isolation has given rise to a distinct freshwater ecoregion with many endemic species.[11]
There are fifteen freshwater fish species, including nine exclusively freshwater species, three
Southwest Australian varieties of the diadromous common galaxias (Galaxias maculatus) and spotted galaxias (Galaxias truttaceus) have adapted so they can live their life-cycle and reproduce in fresh water.[11]
The
History
The first evidence of human habitation of the region was 50,000 years ago at Devil's Lair by ancestors of today's Aboriginal people.[12]
Aboriginal populations were generally denser on the coastal plain and along the coastal forest edge, and in the interior woodlands and shrublands, particularly near permanent streams and river estuaries. Population was sparse in the forested areas of the south. Offshore islands were likely uninhabited.[12]
The Aboriginal inhabitants deliberately set fires to manage the land and vegetation. Evidence from lake and estuarine sediments and firsthand accounts suggest that fire intervals in well-settled areas were frequent – from one to ten years – compared to unoccupied forests and offshore islands, where fire intervals were 30 to 100 or more years. Frequent burning reduced tree cover and encouraged the growth of grasses, herbs, and low shrubs, fostering open woodlands and savannas and limiting areas of dense forest and thicket.[12]
Noongar peoples inhabited the western and southern portions of the region. The Noongar comprised 14 groups, which spoke distinct but mutually-intelligible languages.
The Nyoongar seasonal calendar includes six different seasons in a yearly cycle. These are Birak, Bunuru, Djeran, Makuru, Djilba and Kambarang. Each of the six seasons represents and explains the seasonal changes seen annually. The flowering of many different plants, the hibernation of reptiles and the moulting of swans are all helpful indicators that the seasons are changing.
The first permanent European settlement in the region was in 1826 near present-day Albany. European settlers mostly dispossessed the Aboriginal inhabitants, and established extensive agriculture, including wheat, barley, canola, lupins, and oats. They also introduced sheep and cattle to the region. European settlement also changed the fire regime established by the Aboriginal inhabitants of the land.
Protected areas
109,445 km2, or 22.13%, of Southwest Australia's land area is in protected areas.[13][14][15][16][17][18]
Ecoregion | Area km2 | Area protected km2 | % protected |
---|---|---|---|
Coolgardie woodlands[13] | 137,681 | 44,504.01 | 32.32% |
Esperance mallee[14] | 115,773 | 37,718.84 | 32.58% |
Jarrah-Karri forest and shrublands[15] |
10,467 | 4,759.76 | 45.47% |
Southwest Australia savanna[16] | 169,271 | 14,516.68 | 8.58% |
Southwest Australia woodlands[17] |
46,150 | 5,933.04 | 12.86% |
Swan Coastal Plain scrub and woodlands[18] |
15,259 | 2,012.81 | 13.19% |
Total | 494,601 | 109,445.15 | 22.13% |
See also
References
- ^ Wardell-Johnson, Grant; Wardell-Johnson, Angela; Bradby, K; Robinson, Todd; Bateman, Bill; Williams, K; Braun, K; Beckerling, J; Burbridge, Michael (2016), Application of a Gondwanan perspective to restore ecological integrity in the south-western Australian global biodiversity hotspot, Department of Environment and Agriculture, retrieved 11 October 2016
- ISSN 0311-4546
- ISBN 978-1-74258-564-2
- ^ "The Southwest Australian Biodiversity Hotspot as a Tourist Destination". 31 December 2015.
- ^ a b "Climate of Western Australia". Britannica.com. Accessed 29 April 2022. [1]
- ^ Kala, Jatin; Robson, Belinda; Fontaine, Joe; Beatty, Stephen; and Wernberg, Thomas (2021). "Drying land and heating seas: why nature in Australia’s southwest is on the climate frontline". The Conversation, published 28 October 2021 12.55am EDT.
- PMID 25442328
- ISBN 0-8021-3943-4.
- ^ BirdLife International (2022) Endemic Bird Areas factsheet: South-west Australia. Downloaded from http://www.birdlife.org on 27 April 2022. [2]
- ^ "FloraBase - the Western Australian Flora". Department of Environment and Conservation. Retrieved 25 October 2011.
- ^ a b c d Unmack, Peter. "Southwestern Australia". Freshwater Ecoregions of the World. Accessed 17 June 2020. [3]
- ^ a b c "Hassell, Cleve W., and Dodson, John R. (2003). "The fire history of south-west Western Australia prior to European settlement in 1826-1829". in Fire in ecosystems of south-west Western Australia:Impacts and management. Ian Abbott and Neil Burrows, eds. Backhuys Publishers, 2003, pp. 71–85.
- ^ a b "Coolgardie woodlands". DOPA Explorer. Accessed 29 April 2022. [4]
- ^ a b "Esperance mallee". DOPA Explorer. Accessed 29 April 2022. [5]
- ^ a b "Jarrah-Karri forest and shrublands". DOPA Explorer. Accessed 29 April 2022. [6]
- ^ a b "Southwest Australia savanna". DOPA Explorer. Accessed 29 April 2022. [7]
- ^ a b "Southwest Australia woodlands". DOPA Explorer. Accessed 29 April 2022. [8]
- ^ a b "Swan Coastal Plain scrub and woodlands". DOPA Explorer. Accessed 29 April 2022. [9]
Further reading
- Thackway, R and I D Cresswell (1995) An interim biogeographic regionalisation for Australia : a framework for setting priorities in the National Reserves System Cooperative Program Version 4.0 Canberra : ISBN 0-642-21371-2
External links