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Southwest Australia

April 12, 2023

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

See also: Flora of Western Australia

Southwest Australia is recognized as a floristic province.[7]

Vegetation in the region is mainly woody, including forests, woodlands, shrublands, and heathlands, but no grasslands. Predominant vegetation types are Eucalyptus woodlands, eucalyptus-dominated mallee shrublands, and kwongan shrublands and heathlands, which correspond to the chaparral, matorral, maquis, and fynbos shrublands found in other Mediterranean-type regions. The region has generally nutrient-poor sandy or lateritic soils, which has encouraged rich speciation of plants adapted to specific ecological niches. The region hosts a great diversity of endemic species, notably among the protea family (Proteaceae).[citation needed]

Southwest Australia is home to many endemic carnivorous plants, including more than half the world's species of sundews (Drosera), the bladderwort subgenus Polypompholyx, the Byblis gigantea complex of rainbow plants (composed of two species, Byblis lamellata and B. gigantea), and the pitcher plant Cephalotus follicularis, sole species in the plant family Cephalotaceae.[8]

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 Endemic Bird Area, with several endemic species of birds including the long-billed black cockatoo (Zanda baudinii), western corella (Cacatua pastinator), noisy scrubbird (Atrichornis clamosus), red-winged fairywren (Malurus elegans), western bristlebird (Dasyornis longirostris), black-throated whipbird (Psophodes nigrogularis), white-breasted robin (Eopsaltria georgianus), and red-eared firetail (Stagonopleura oculata).[9] The western rufous bristlebird (Dasyornis broadbenti litoralis), an endemic subspecies of rufous bristlebird, is now extinct.[citation needed]

Ecoregions

The World Wide Fund for Nature and Interim Biogeographic Regionalisation for Australia (IBRA) divide the region into six ecoregions and ten biogeographic regions:

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 Eremaean Region by the Western Australian Herbarium.[10]

Freshwater

See also: South West drainage division

Southwest Australia has several permanent rivers and streams, including the Swan–Avon system, the Blackwood River, and other short rivers. The perennial rivers drain from the interior plateau and Darling Range across the coastal plain. Their flow is strongly seasonal, corresponding to the Southwest's wet winter–dry summer weather pattern. The perennial streams extend from east of Esperance on the south coast to the Arrowsmith River north of Perth, most often in areas with 700 mm or more of annual rainfall.[11]

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 estuarine species adapted to brackish water, and three diadromous species that spend part of their life-cycle in the sea. The exclusively freshwater species are endemic to Southwest Australia, as are two estuarine species. The salamanderfish (Lepidogalaxias salamandroides) is the sole species in the endemic family Lepidogalaxiidae. Salamanderfish can aestivate during the summer months, an adaptation to the region's dry summers. Other endemic species are the nightfish (Bostockia porosa), western mud minnow (Galaxiella munda), black-stripe minnow (Galaxiella nigrostriata), Balston’s pygmy perch (Nannatherina balstoni),[11] western pygmy perch (Nannoperca vittata), and western galaxias (Galaxias occidentalis).

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 southwestern snake-necked turtle (Chelodina colliei) and western swamp turtle (Pseudemydura umbrina) are aquatic species endemic to Southwest Australia.

History

Further information: History of Australia

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

  1. ^ 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
  2. ^ Burbidge, Andrew (1 February 2010), "Global hotspot under stress: while the south-west corner of Western Australia is recognised as a global biodiversity hotspot, its unique ecosystems have suffered land clearing, introduced pests and weeds, a changed fire regime, loss of water and salinisation. climate change may tip the balance for some species, unless effective action is taken.(Focus)", Ecos, CSIRO Publishing (153): 18(2), ISSN 0311-4546
  3. ^ Lambers, H., ed. (2014), Plant life on the sandplains in southwest Australia : a global biodiversity hotspot : kwongan matters, Crawley, Western Australia UWA Publishing, ISBN 978-1-74258-564-2
  4. ^ "The Southwest Australian Biodiversity Hotspot as a Tourist Destination". 31 December 2015.
  5. ^ a b "Climate of Western Australia". Britannica.com. Accessed 29 April 2022. [1]
  6. ^ 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.
  7. ^ Cook, Lyn G; Hardy, Nate B; Crisp, Michael D (2015), "Three explanations for biodiversity hotspots: small range size, geographical overlap and time for species accumulation. An Australian case study", New Phytologist, Wiley Subscription Services, Inc (published 1 July 2015), 207 (2): 390–400, doi:10.1111/nph.13199, ISSN 0028-646X, PMID 25442328
  8. ^ Flannery, Tim (1994). The Future Eaters.. Grove Press. ISBN 0-8021-3943-4.
  9. ^ BirdLife International (2022) Endemic Bird Areas factsheet: South-west Australia. Downloaded from http://www.birdlife.org on 27 April 2022. [2]
  10. ^ "FloraBase - the Western Australian Flora". Department of Environment and Conservation. Retrieved 25 October 2011.
  11. ^ a b c d Unmack, Peter. "Southwestern Australia". Freshwater Ecoregions of the World. Accessed 17 June 2020. [3]
  12. ^ a b c "Hassell, Cleve W., and Dodson, John R. (2003). "The fire history of south-west Western Australia prior to European settlment 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.
  13. ^ a b "Coolgardie woodlands". DOPA Explorer. Accessed 29 April 2022. [4]
  14. ^ a b "Esperance mallee". DOPA Explorer. Accessed 29 April 2022. [5]
  15. ^ a b "Jarrah-Karri forest and shrublands". DOPA Explorer. Accessed 29 April 2022. [6]
  16. ^ a b "Southwest Australia savanna". DOPA Explorer. Accessed 29 April 2022. [7]
  17. ^ a b "Southwest Australia woodlands". DOPA Explorer. Accessed 29 April 2022. [8]
  18. ^ 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 : Australian Nature Conservation Agency, Reserve Systems Unit, 1995. ISBN 0-642-21371-2

External links

 
Wikimedia Commons has media related to Southwest Australia.

    April 12, 2023
    southwest, australia, biogeographic, region, western, australia, includes, mediterranean, climate, area, southwestern, australia, which, home, diverse, distinctive, flora, fauna, ecoregions, defined, jarrah, karri, forest, shrublands, woodlands, swan, coastal,. 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 Ecoregions of Southwest Australia as defined by the WWF 1 Jarrah Karri forest and shrublands 2 Southwest Australia woodlands and Swan Coastal Plain 3 Southwest Australia savanna 4 Coolgardie woodlands 5 Esperance mallee The region is also known as the Southwest Australia Global Diversity Hotspot 1 2 3 4 Contents 1 Geography 2 Climate 3 Flora 4 Fauna 5 Ecoregions 6 Freshwater 7 History 8 Protected areas 9 See also 10 References 11 Further reading 12 External linksGeography EditThe 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 EditThe 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 EditSee also Flora of Western Australia Southwest Australia is recognized as a floristic province 7 Vegetation in the region is mainly woody including forests woodlands shrublands and heathlands but no grasslands Predominant vegetation types are Eucalyptus woodlands eucalyptus dominated mallee shrublands and kwongan shrublands and heathlands which correspond to the chaparral matorral maquis and fynbos shrublands found in other Mediterranean type regions The region has generally nutrient poor sandy or lateritic soils which has encouraged rich speciation of plants adapted to specific ecological niches The region hosts a great diversity of endemic species notably among the protea family Proteaceae citation needed Southwest Australia is home to many endemic carnivorous plants including more than half the world s species of sundews Drosera the bladderwort subgenus Polypompholyx the Byblis gigantea complex of rainbow plants composed of two species Byblis lamellata and B gigantea and the pitcher plant Cephalotus follicularis sole species in the plant family Cephalotaceae 8 Fauna EditThe 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 Endemic Bird Area with several endemic species of birds including the long billed black cockatoo Zanda baudinii western corella Cacatua pastinator noisy scrubbird Atrichornis clamosus red winged fairywren Malurus elegans western bristlebird Dasyornis longirostris black throated whipbird Psophodes nigrogularis white breasted robin Eopsaltria georgianus and red eared firetail Stagonopleura oculata 9 The western rufous bristlebird Dasyornis broadbenti litoralis an endemic subspecies of rufous bristlebird is now extinct citation needed Ecoregions EditThe 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 Eremaean Region by the Western Australian Herbarium 10 Freshwater EditSee also South West drainage division Southwest Australia has several permanent rivers and streams including the Swan Avon system the Blackwood River and other short rivers The perennial rivers drain from the interior plateau and Darling Range across the coastal plain Their flow is strongly seasonal corresponding to the Southwest s wet winter dry summer weather pattern The perennial streams extend from east of Esperance on the south coast to the Arrowsmith River north of Perth most often in areas with 700 mm or more of annual rainfall 11 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 estuarine species adapted to brackish water and three diadromous species that spend part of their life cycle in the sea The exclusively freshwater species are endemic to Southwest Australia as are two estuarine species The salamanderfish Lepidogalaxias salamandroides is the sole species in the endemic family Lepidogalaxiidae Salamanderfish can aestivate during the summer months an adaptation to the region s dry summers Other endemic species are the nightfish Bostockia porosa western mud minnow Galaxiella munda black stripe minnow Galaxiella nigrostriata Balston s pygmy perch Nannatherina balstoni 11 western pygmy perch Nannoperca vittata and western galaxias Galaxias occidentalis 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 southwestern snake necked turtle Chelodina colliei and western swamp turtle Pseudemydura umbrina are aquatic species endemic to Southwest Australia History EditFurther information History of Australia 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 Edit109 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 protectedCoolgardie 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 EditSouth West Western Australia South West Seismic ZoneReferences Edit 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 Burbidge Andrew 1 February 2010 Global hotspot under stress while the south west corner of Western Australia is recognised as a global biodiversity hotspot its unique ecosystems have suffered land clearing introduced pests and weeds a changed fire regime loss of water and salinisation climate change may tip the balance for some species unless effective action is taken Focus Ecos CSIRO Publishing 153 18 2 ISSN 0311 4546 Lambers H ed 2014 Plant life on the sandplains in southwest Australia a global biodiversity hotspot kwongan matters Crawley Western Australia UWA Publishing 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 Cook Lyn G Hardy Nate B Crisp Michael D 2015 Three explanations for biodiversity hotspots small range size geographical overlap and time for species accumulation An Australian case study New Phytologist Wiley Subscription Services Inc published 1 July 2015 207 2 390 400 doi 10 1111 nph 13199 ISSN 0028 646X PMID 25442328 Flannery Tim 1994 The Future Eaters Grove Press 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 settlment 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 EditThackway 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 Australian Nature Conservation Agency Reserve Systems Unit 1995 ISBN 0 642 21371 2External links Edit Wikimedia Commons has media related to Southwest Australia Biodiversityhotspots org Conservation International Southwest Australia Retrieved from https en wikipedia org w index php title Southwest Australia amp oldid 1146597295, wikipedia, wiki, book, books, library,

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