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The flora ofAustralia comprises a vast assemblage of plant species estimated to over 21,000vascular and 14,000non-vascular plants, 250,000 species offungi and over 3,000lichens. The flora has strong affinities with the flora ofGondwana, and below thefamily level has a highlyendemicangiosperm flora whose diversity was shaped by the effects ofcontinental drift and climate change since theCretaceous. Prominent features of the Australian flora are adaptations toaridity and fire which includescleromorphy andserotiny. These adaptations are common in species from the large and well-known familiesProteaceae (Banksia),Myrtaceae (Eucalyptus - gum trees), andFabaceae (Acacia - wattle).
The arrival of humans around 50,000 years ago[2][3] and the settlement byEuropeans from 1788, has had a significant impact on the flora. The use offire-stick farming by Aboriginal people led to significant changes in the distribution of plant species over time, and the large-scale modification or destruction of vegetation for agriculture and urban development since 1788 has altered the composition of most terrestrial ecosystems, leading to the extinction of 61 plant species by 2006, and endangering over 1000 more.
In Australiaforest cover is around 17% of the total land area, equivalent to 134,005,100 hectares (ha) of forest in 2020, up from 133,882,200 hectares (ha) in 1990. In 2020, naturally regenerating forest covered 131,614,800 hectares (ha) and planted forest covered 2,390,300 hectares (ha). Of the naturally regenerating forest 0% was reported to beprimary forest (consisting of native tree species with no clearly visible indications of human activity) and around 18% of the forest area was found within protected areas. For the year 2015, 67% of the forest area was reported to be underpublic ownership, 32%private ownership and 1% with ownership listed as other or unknown.[4][5]
Australia was part of the southern supercontinentGondwana, which also includedSouth America,Africa,India andAntarctica. Most of the modern Australian flora had their origin in Gondwana during theCretaceous when Australia was covered in subtropical rainforest. Australian ferns and gymnosperms bear a strong resemblance to their Gondwanan ancestors,[6] and prominent members of the early Gondwanan angiosperm flora such as theNothofagus,Myrtaceae andProteaceae were also present in Australia.[7]
Gondwana began to break up 140 million years ago (MYA); 50 MYA during theEocene Australia separated from Antarctica, and was relatively isolated until the collision of theIndo-Australian Plate with Asia in theMiocene era 5.3 MYA. As Australiadrifted, local and globalclimatic change had a significant and lasting effect: a circumpolar oceanic current developed, atmospheric circulation increased as Australia moved away from Antarctica, precipitation fell, there was a slow warming of the continent andarid conditions started to develop.[8] These conditions of geographic isolation and aridity led to the development of a more complex flora. From 25 to 10 MYA pollen records suggest the rapid radiation of species likeEucalyptus,Casuarina,Allocasuarina,Banksia and thepea-flowered legumes, and the development of open forest; grasslands started to develop from theEocene. Collision with theEurasian Plate also led to additionalSouth-east Asian andcosmopolitan elements entering the flora like theLepidium andChenopodioideae.[9]
The development of aridity and the old and nutrient poor soils of the continent led to some unique adaptations in the Australian flora and evolutionary radiation of genera – likeAcacia andEucalyptus – that adapted to those conditions. Hard leaves with a thickouter layer, a condition known asscleromorphy, andC4 andCAM carbon fixation which reduce water loss during photosynthesis are two common adaptations in Australian arid-adapted dicot and monocot species respectively.
Rising aridity also increased the frequency of fires in Australia. Fire is thought to have played a role in the development and distribution of fire-adapted species from theLate Pleistocene. An increase in charcoal in sediment around 38,000 years ago coincides with dates for the inhabitation of Australia by theIndigenous Australians and suggests that man-made fires, from practices likefire-stick farming, have played an important role in the establishment and maintenance of sclerophyll forest, especially on the east coast of Australia.[10] Adaptations to fire includelignotubers and epicormic buds inEucalyptus andBanksia species that allow fast regeneration following fire. Some genera also exhibitserotiny, the release of seed only in response to heat and/or smoke.Xanthorrhoea grass trees and some species of orchids only flower after fire.[11]
In biogeography and zoogeography, Australia alone is sometimes considered arealm (Australian realm), while some authors unite the area with other regions to form theAustralasian realm.
In phytogeography, the area is considered a floristic kingdom (Australian kingdom), with the following endemic families, according to Takhtajan: Platyzomataceae (now included inPteridaceae),Austrobaileyaceae, Idiospermaceae (now part ofCalycanthaceae),Gyrostemonaceae,Baueraceae,Davidsoniaceae,Cephalotaceae,Eremosynaceae,Stylobasiaceae,Emblingiaceae,Akaniaceae,Tremandraceae,Tetracarpaeaceae,Brunoniaceae,Blandfordiaceae,Doryanthaceae,Dasypogonaceae andXanthorrhoeaceae. It is also thecenter of origin ofEupomatiaceae,Pittosporaceae,Epacridaceae,Stackhousiaceae,Myoporaceae andGoodeniaceae. Other families with high occurrences arePoaceae,Fabaceae,Asteraceae,Orchidaceae,Euphorbiaceae,Cyperaceae,Rutaceae,Myrtaceae (speciallyLeptospermoideae) andProteaceae.[12][13]
Australia's terrestrial flora can be collected into characteristicvegetation groups. The most important determinant is rainfall, followed by temperature which affects water availability.[14] Several schemes of varying complexity have been created. As of 2022, the NVIS (National Vegetation Information System) divides Australia's terrestrial flora into 33Major Vegetation Groups,[15] and 85Major Vegetation Subgroups.[16]
According to the scheme the most common vegetation types are those that are adapted to arid conditions where the area has not been significantly reduced by human activities such as land clearing for agriculture. The dominant vegetation type in Australia is the hummock grasslands that occur extensively in arid Western Australia, South Australia and the Northern Territory. It accounts for 23% of the native vegetation, the predominant species of which are from the genusTriodia.Zygochloa also occurs in inland sandy areas like theSimpson Desert.
A further 39% of native vegetation is covered by a combination of:
Other groups with restricted areas of less than 70,000 square kilometres include tropical or temperate rainforest andvine thickets, tall or open eucalypt forests,Callitris andCasuarina forests, and woodlands and heath.
Australia has over 21,077 described species of vascular plants,[19] these include theangiosperms, seed-bearing non-angiosperms (like the conifers and cycads), and the spore-bearing ferns and fern allies.[20] Of these about 11% are naturalised species; the remainder are native or endemic.[21] The vascular plant flora has been extensively catalogued, the work being published in the ongoingFlora of Australia series. A list of vascular plant families represented in Australia using theCronquist system is also available.[22]
At the higher taxonomic levels the Australian flora is similar to that of the rest of the world; most vascular plant families are represented within the native flora, with the exception of thecacti,birch and a few others, while nine families occur only in Australia.[23][24] Australia's vascular flora is estimated to be 85% endemic;[25] this high level of vascular plant endemism is largely attributable to the radiation of some families like theProteaceae,Myrtaceae, andFabaceae.
| Family | % of total flora1 | Notable genera |
|---|---|---|
| Fabaceae | 12.0 | Acacia,Pultenaea,Daviesia,Bossiaea |
| Myrtaceae | 9.3 | Callistemon,Eucalyptus,Melaleuca,Leptospermum |
| Asteraceae | 8.0 | Brachyscome,Olearia |
| Poaceae | 6.5 | Triodia |
| Proteaceae | 5.6 | Banksia,Hakea,Grevillea |
| Cyperaceae | 3.3 | Cyperus |
| Orchidaceae | 3.0 | Caladenia,Pterostylis |
| Ericaceae | 2.1 | Leucopogon,Epacris |
| Euphorbiaceae | 2.0 | Ricinocarpos |
| Rutaceae | 1.8 | Boronia,Correa,Citrus |
| 1 Based on total number of species | ||
The native Australian flora contains manymonocotyledons. The family with the most species is thePoaceae which includes a huge variety of species, from the tropical bambooBambusa arnhemica to the ubiquitous spinifex that thrives in arid Australia from the genusTriodia. There are more than 800 described species oforchid in Australia.[26] About one quarter of these are epiphytes. The terrestrial orchids occur across most of Australia, the majority of species beingdeciduous – their aboveground parts die back during the dry season and they re-sprout from a tuber when it rains.
Other families with well-known representatives include the alpine Tasmanianbutton grass, which form tussock-like mounds from theCyperaceae; the genusPatersonia of temperate iris-like forbs from theIridaceae; and, thekangaroo paws from the familyHaemodoraceae. TheXanthorrhoea grass trees, thescrew palms of thePandanaceae andpalms are large monocots present in Australia. There are about 57 native palms; 79% of these only occur in Australia.[27]
Thedicots are the most diverse group of angiosperms. Australia's best known species come from three large and very diverse dicot families: theFabaceae, theMyrtaceae and theProteaceae. The Myrtaceae is represented by a variety of woody species; gum trees from the generaEucalyptus,Corymbia andAngophora, Lillipillies (Syzygium), the water-lovingMelaleuca andBottlebrush and the shrubbyDarwinia andLeptospermum, commonly known as teatrees, andGeraldton wax. Australia is also acentre of diversity for the Proteaceae, with woody, well-known genera such asBanksia,Dryandra,Grevillea,Hakea, thewaratah and Australia's only commercial native food crop, themacadamia. Australia also has representatives of all three legume subfamilies.Caesalpinioideae is notably represented byCassia trees. TheFaboideae or pea-flowered legumes are common and many are well known for their flowers, including thegolden peas,Glycine species and theSturt's desert pea. TheMimosoideae is best known for the huge genusAcacia which includes Australia's floral emblem thegolden wattle.
Many plant families that occur in Australia are known for their floral displays that follow seasonal rains. TheAsteraceae is well represented by its subfamilyGnaphalieae, which included the paper or everlasting daisies; this group has its greatest diversity in Australia. Other families with flowering shrubs include theRutaceae, with the fragrantBoronia andEriostemon, theMyoporaceae with theEremophila, and members of theEricaceae with Victoria's Floral EmblemEpacris impressa.
Amongst the most ancient species of flowering hardwood trees are theCasuarinaceae, includingbeach, swamp andriver oaks, andFagaceae represented in Australia by three species ofNothofagus. Trees of theRosales are notably represented by theMoraceae whose species include theMoreton Bay Fig and thePort Jackson Fig, and theUrticaceae whose members include several tree sized stinging nettles;Dendrocnide moroides is the most virulent. There are also numeroussandalwood species including thequandongs and native cherry,Exocarpus cupressiformis. Thebottle tree of theSterculiaceae is one of 30 tree species from theBrachychiton. There are about 75 nativemistletoes thatparasitise Australian tree species, including two terrestrial parasitic trees, one of which is the spectacularWestern Australian Christmas tree.
Australia's salt marshes and wetlands are covered by a large variety of salt and drought tolerant species from theAmaranthaceae which include the saltbushes (Atriplex) and bluebushes (Maireana andChenopodium). Many of these plants have succulent leaves; other native succulents are from the generaCarpobrotus,Calandrinia andPortulaca. Succulent stems are present in many of theEuphorbiaceae in Australia, though the best known members are the non-succulent looking fragrant Wedding bushes of the genusRicinocarpos.Carnivorous plants which favour damp habitats are represented by four families including thesundews,bladderworts, pitcher-plants from theCephalotaceae, which are endemic toWestern Australia, and theNepenthaceae.
Aquatic monocots and dicots both occur in Australian waters. Australia has about 51,000 square kilometres ofseagrass meadows and the most diverse group seagrass species in the world. There are 22 species found in temperate waters and 15 in tropical waters out of a known 70 species worldwide.[28] Aquatic dicots include themangroves; in Australia there are 39 mangrove species that cover 11,500 square kilometres and comprise the third largest area of mangroves in the world.[29] Other native aquatic dicots here includewater lilies andwater milfoils.
Gymnosperms present in Australia include thecycads andconifers. There are 69 species of cycad from 4 genera and 3 families of eastern and northern Australia, with a few in south-western Western Australia and central Australia[clarification needed]. Native conifers are distributed across 3 taxonomic families (Cupressaceae,Podocarpaceae,Araucariaceae), 14 genera and 43 species, of which 39 are endemic. Most species are present in wetter mountainous areas consistent with their Gondwanan origins, including the generaAthrotaxis,Actinostrobus,Microcachrys,Microstrobos,Diselma and the TasmanianHuon pine, sole member of the genusLagarostrobos.Callitris is a notable exception; species from this genus are found mainly in drier open woodlands.[30] The most recently discovered species of conifer is theliving fossilWollemi pine, which was first described in 1994. Although many Australian conifers are referred to as 'pines', there are no members of the pine family (Pinaceae) native to Australia.
Spore bearing vascular plants include theferns andfern allies. True ferns are found over most of the country and are most abundant in tropical and subtropical areas with high rainfall. Australia has a native flora of 30 families, 103 genera and 390 species of ferns, with another 10 species being naturalised. The "fern allies" are represented by 44 native species ofwhisk ferns,horsetails andlycophytes.[30] Ferns prefer a cool and damp environment since water is required for reproduction, the majority of Australian species are found in bushland[clarification needed] and rainforest, there are aquatic, epiphytic (Platycerium,Huperzia andAsplenium), and terrestrial species including large tree ferns from the generaCyathea andDicksonia.
Thealgae are a large and diverse group of photosynthetic organisms. Many studies of algae include thecyanobacteria, in addition to micro and macroeukaryotic types that inhabit both fresh and saltwater. Currently, about 10,000 to 12,000 species of algae are known for Australia.[31] The algal flora of Australia is unevenly documented: northern Australia remains largely uncollected for seaweeds and marine phytoplankton, descriptions of freshwater algae are patchy, and the collection of terrestrial algae has been almost completely neglected.[32]
Thebryophytes –mosses,liverworts andhornworts – are primitive, usually terrestrial, plants that inhabit the tropics, cool-temperate regions and montane areas; there are some specialised members that are adapted to semi-arid and arid Australia. There are slightly fewer that 1,000 recognised species of moss in Australia. The five largest genera are theFissidens,Bryum,Campylopus,Macromitrium andAndreaea.[33] There are also over 800 species of liver- and horn-worts in 148 genera in Australia.[34]
The fungal flora of Australia is not well characterised; Australia is estimated to have about 250,000 fungal species of which roughly 5% have been described. Knowledge of distribution, substrates and habitats is poor for most species, with the exception of common plant pathogens.[35]
Lichens are composite organisms comprising, in most cases, an Ascomycete fungus and a unicellular green alga, their classification is based on the type of fungi. The lichen flora of Australia and its island territories, includingChristmas Island,Heard Island,Macquarie Island andNorfolk Island, currently comprises 3,238 species and infra-specific taxa in 422 genera, 34% of which are considered to be endemic.[36]
The first Australian plants recognised and classified in Linnaean taxonomy were a species ofAcacia andSynaphea in 1768 asAdiantum truncatum andPolypodium spinulosum respectively by Dutch philologistPieter Burman the Younger, who stated they were from Java. Later, both were found to be from Western Australia, likely to have been collected near the Swan River, possibly on a 1697 visit there of fellow DutchmanWillem de Vlamingh.[37] This was followed byCook's expedition making landfall at what is nowBotany Bay in April 1770, and the early work ofBanks, Solander and Parkinson.[who?] Botanical exploration was enabled by thefounding of the permanent colony at Port Jackson in 1788, and the subsequent expeditions along Australia's coastline.[37]
The Australian flora was utilised by theIndigenous inhabitants of Australia. Indigenous Australians used thousands of species for food, medicine, shelter, tools and weapons.[38] For example, the starchy roots ofClematis microphylla were used in western Victoria to make a dough that was baked, and the leaves of the plant were used as a poultice applied to skin irritations and blisters.[39]
Forestry species include a number of eucalypts used for paper and timber,huon pine,hoop pine,cypress pine,Australian Blackwood, and sandalwood fromSantalum spicatum andS. lanceolatum. A significant area used by the pastoral industry is based on native pasture species includingMitchell grass,saltbush,bluebush,wallaby grass,spear grass,tussock grasses andkangaroo grass.[citation needed]
Until recently themacadamia nut andTetragonia tetragonoides were the only Australian food plant species widely cultivated. Although commercial cultivation of macadamia started in Australia in the 1880s, it became an established large-scale crop inHawaii.[40][41] The development of a range of native food crops began in the late 1970s with the assessment of species forcommercial potential. In the mid-1980s restaurants and wholesalers started to market various native food plant products. These includedwattles for their edible seeds;Davidson's Plum,desert lime,finger lime,quandong,riberry,Kakadu plum,muntries,bush tomato,Illawarra plum for fruit;warrigal greens as a leaf vegetable; and,lemon aspen,lemon myrtle,mountain pepper as spices. A few Australian native plants are used by the pharmaceutical industry, such as twoscopolamine andhyoscyamine producingDuboisia species andSolanum aviculare andS. laciniatum for the steroidsolasodine. Essential oils fromMelaleuca,Callitris,Prostanthera,Eucalyptus andEremophila are also used medicinally. Due to the wide variety of flowers and foliage, Australian plant species are also popular for floriculture internationally.
Modification of the Australian environment by Indigenous Australians and following European settlement has affected the extent and the distribution of the flora.
The changes since 1788 have been rapid and significant: displacement of Indigenous Australians disrupted fire régimes that had been in place for thousands of years; forestry practices have modified the structure of native forests; wetlands have been filled in; and broad scale land-clearing for crops, grazing and urban development has reduced native vegetation cover and led to landscape salinisation, increased sediment, nutrient and salt loads in rivers and streams, loss of habitat and a decline in biodiversity.[42] The intentional and unintentional release ofinvasive plant and animal species into delicate ecosystems is a major threat to floral biodiversity; 20 introduced species have been declaredWeeds of National Significance.[43]
As of 2006, 61 plant species were known to have become extinct since European settlement; and a further 1,239 species were considered threatened.[44]
Protected areas have been created in every state and territory to protect and preserve the country's unique ecosystems. These protected areas include national parks and other reserves, as well as 64 wetlands registered under theRamsar Convention and 16World Heritage Sites. As of 2002, 10.8% (774,619.51 km2) of the total land area of Australia is within protected areas.[45] Protected marine zones have been created in many areas to preserve marine biodiversity; as of 2002, these areas cover about 7% (646,000 km2) of Australia's marine jurisdiction.[46]
In 2003, the Australian Government's Threatened Species Scientific Committee identified 15biodiversity hotspots in Australian and 85 characteristic ecosystems, as classified by the Interim Biogeographic Regionalisation for Australia. Some effort is being made to ensure each is represented within a protected area under Australia'sBiodiversity Action Plan.[47][48]
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