Green Flora of Australia
Australia is host to a vast variety of plant life. It is estimated that over 34,000 species of plants and 253,000 species of fungi and lichens make Australia their home. It is theorized that much of the flora evolved from ancient species originating on the supercontinent of Gondwana before continental drift formed the Australia continent of today. Australian flora is noted for its adaptability to arid climates and fire through scleromorphy, plants with hardy leaves, and serotiny, plants that release seeds in response to harsh environmental triggers. These traits are apparent in some of Australia’s most notable species in the plant kingdom, such as the Banksia, Eucalyptus, and Acacia. The green flora of Australia has been affected through history by indigenous Australians 60,000 years ago and by Europeans from just over 200 years ago. Agricultural and urban development over the past two centuries has played the largest role in the alteration of the native ecosystem and the role played in it by the green flora of Australia.
Ancient Green Flora of Australia
It is theorized that Australia was part of the ancient supercontinent of Gondwana that included Antarctica, India, Africa, and South America. Most of the flora of modern Australia derived from this time dating back 140 million years. As Australia broke off from the supercontinent and was set adrift in isolation, local climate change had a major impact on the evolution of green flora. The isolation and northward movement of the continent led to the development of a diverse ecology. From the Eocene period, much of today’s staple green flora of Australia developed. Not only the aforementioned species, but legumes, open forests, and grasslands came into being.
The arid climate and poor soil led to very unique adaptations in the green flora of Australia. Hard leaves, resistant to the elements developed, reducing moisture loss. The frequency of fires due to the arid climate led to the development of fire-adapted species in the Pleistocene era. Even as soon as 38,000 years ago, indigenous Australians were found to have changed the flora of the continent through fire-stick farming.
Types of Green Flora
The green flora of Australia has been classified according to vegetation groups based on the characteristics of the flora. The most defining characteristics are based on the climate: rainfall and temperature. The third-largest factor is the availability of water, which is more of an environmental factor.
Although several schemes have been created in the classification of Australian flora, the most recent is that of the Natural Heritage Trust. This scheme classifies Australia’s entire flora into 30 vegetation groups and 67 subgroups. According to the scheme, the most common flora is the hummock grasslands of the most arid regions. They can be found in the Northern Territory, South Australia, and Western Australia. These grasses are estimated to be 23 percent of the total green flora of Australia. The most common genus is Triodia followed by Zygochloa.
According to the Natural Heritage Trust scheme, the following types of vegetation comprise the next 39 percent of green flora:
- Eucalyptus forest – These occur mainly in areas between the grasslands and the tropical rainforests. Tree growth is limited here, but Eucalyptus thrives among the grasses and shrubs on the ground. The largest area of Eucalyptus is in Queensland.
- Acacia forest – These forests are predominant in semi-arid regions. The largest of such regions is in Western Australia. Specific species include brigalow, gidgee, lancewood, mulga, and bendee.
- Shrub lands – These areas are in both semi-arid and arid regions. They include Acacia trees, most often mulga, and are most notable in Western Australia.
- Tussock grasslands – These lands are in semi-arid and temperate zones. The largest tussock grasslands are in Queensland. The lands are composed of a wide variety of up to 10 genera of grasses.
- Shrub and forblands – These are predominant in arid and semi-arid areas. The species here are notable for their tolerance to salt and drought. Western Australia and South Australia are abundant in these species.
- Restricted areas – These are areas of 70,000 km square or less of rainforest. They include thickets, eucalyptus forest, Casuarina forest, and Heathlands.
The vascular green flora of Australia includes over 20,000 species. Of these, 89 percent are native and 11 percent are naturalised. Vascular flora of the continent has been extensively categorized and catalogued. The categories include angiosperms, non-angiosperms, and spore-bearing flora.
Among angiosperms in Australia, the dicots have the most diversity. The most popular of flora species in Australia are dicots. These include flora of the Fabaceae, Myrtaceae, and Proteaceae families. Among the woody species of the Myrtaceae family are the following:
- Geraldton wax
The Proteaceae are represented by such genera as Hakea, Dryandra, Banksia, and Grevilea.
Another most abundant floral type is the legume subfamilies. These consist most notably of the Caesalpinioideae such as the Cassia tree. Also notable are the pea-flowered legumes of Faboideae that include golden peas and Sturt’s desert peas.
The Mimosoideae consists of the large genus of Acacia, such as the golden wattle.
Seasonal rains bring out notable floral displays among many Australian families of flora. The diverse group of Australian daisies is the most predominant. Flowering shrubs of note include many fragrant varieties such as Boronia, Eriostemon, Rutaceae, Eremophila, and the floral emblem of Victoria, the Epacris impressa.
Other notable angiosperms are ancient flowering hardwoods that include several varieties of oak. Fig trees and sandalwood are also quite abundant. In the salt marshes, species tolerant of drought exist such as saltbushes and bluebushes. Succulents exist in these areas.
This group of seed-bearing green Australia flora is mostly composed of conifers and cycads. The groups are very diverse with over 69 cycad species and native pine trees of 43 species.
Also included in the non-angiosperm green flora of Australia are spore-bearing plants. Ferns are easily found in the tropical and subtropical regions of the continent. Over 390 species of ferns have been catalogued to date.