Native Flora
Native flora are important to the environment, because of their adaptation to the soil, topography and climate of the local area and their help in maintaining an overall ecological balance.
The Murray-Darling Basin represents such diverse environments and as a consequence of this it has an enormous array of plant types. From truly aquatic to semi aquatic to terrestrial, some depend heavily on water while others in arid regions hardly see a drop.
Aquatic Plants
Aquatic plants are often called "macrophytes" These plants are important in improving water quality and providing habitat and food for other species. Some macrophytes live with their leaves fully submerged in water, occasionally these plants float to the surface with their roots dangling below but usually their roots are attached to the sediment. Others are known as emergent macrophytes and have their roots in the sediments, but foliage that emerges out of the water. They often are found along the water’s edge.
 | The submerged plants that are commonly found are the water primrose (Ludwigia pepliodies), and floating-leafed pondweed (Potamogeton tricarinatus) these have their roots in mud and their stems and/or leaves floating.
Ribbon weed (Vallisneria spp.) is one of the most widespread submerged aquatic plants in the world. Within the Murray-Darling Basin it is found in standing water or slow-flowing aquatic habitats such as rivers and creeks, lakes and billabongs, as well as in drains and dams. | Sedges and rushes are typical emergent plants. These occur frequently in wetlands, floodplains and riparian zones. Species such as the common reed (Phagmites australis), Cumbungi or bull rush ( orientalis and Typha domingensis) and Juncus spp are found through out the basin.
These aquatic plants are strongly dependent on the amount of water present. During droughts these plants can remain dormant as tubers or rhizomes in the mud for several years until the water returns. <Top of Page>
Terrestrial Plants
There are three dominant tree species found on the Murray-Darling Basin's floodplain. These are the River Red Gum (Eucalyptus camaldulensis), Black Box (Eucalyptus largiflorens) and Coolibah (Eucalyptus coolibah).
 | River Red Gums are one of the best known and widely used tree species in Australia. They form extensive forests in sections along the Murray and Murrumbidgee rivers but generally they tend to restrict to a narrow fringe lining the main channel, with an open woodland form. Red gums are an important part of the ecology along the river as they support a large and varied wildlife population and are an indicator of floodplain health. |
Black box occurs in areas flooded less frequently and grow mainly in the southern and western parts of the Basin. A small to medium tree with dark rough trunks and sliver-grey leaves. There is less known about their ecology however like the River Red gum they are an important habitat for birds, lizards and mammals.
Coolibah is a medium height tree that forms open woodlands, usually on heavy clay floodplain soils in the north and western parts of the basin. The coolibah woodlands are habitat for smaller fauna such as bats and rodents. Like the black box, coolibahs are tolerant to relatively long dry conditions as well as periodic flooding.
Some of the undergrowth or shrubland types of plants that occur in the Murray-Darling Basin include lignum (Muehlenbeckia florulenta), nitre bush (Nitraria billardieri) and old man saltbush (Atriplex nummularia). These are generally associated with drier sometimes more saline floodplains. They provide valuable nesting sites and habitat for small animals (including fish during times of flood).
Spiny mudgrass (Pseudoraphis spinescens) is a common species of grass found in the Murray-Darling Basin. It forms grasslands in open areas of frequent or near annual seasonal flooding. It is mainly found in the southern part of the basin usually in shallow depressions of River Red Gum forests. Water couch (Paspalum distichum) grasslands occur on the floodplains of the Macquarie and Gwydir rivers and can sustain grazing provided it is not water stressed. Another significant grass is canegrass (Eragrostis australasica) which is sometimes described as tussock grass. This grass occurs as extensive grasslands in the drier and northern and western parts of the basin. Pre-European Flora At the time of European settlement the range of flora and fauna species included 85 mammals, 367 birds, 151 reptiles, 24 frogs and 20 fish. Although some have become extinct and others are threatened, the biodiversity of the region makes it one of Australia's most important. Today, the Murray Darling Basin still contains a diverse range of plants but is dominated by River Red Gums and Black Box. The native plants of the River Murray play an important role in supporting native animals in the area and maintaining the structural stability of the River Murray (amongst other things). At least half of the pre-European vegetation cover of the River Murray Basin has been removed and replaced by new plants. Significant degradation has resulted. The land's vegetation cover is never static, especially over the longer term. The Australian continent has been subject to various climatic changes, not least those associated with the most recent ice ages, all of which resulted in significant changes to the vegetation. To such evolutionary changes must be added those resulting from the thousands of years of Aboriginal occupation. The European impacts, in no more than two hundred years and a very much shorter period over most of the Basin, have been both intensive and extensive (Carnahan et al. 1990, 54). This was the period that Eric Rolls has called "our white adolescence". Land clearing on a massive scale has taken place (Walker et al. 1993), replacing the diverse native vegetation with agricultural landscapes, plantation and regrowth forests, urban areas and communication corridors. In fact, for Australia as a whole, recent studies have indicated that over 20 per cent of the native vegetation has been cleared for agricultural and other purposes, compared with previous estimates of 6 to 8 per cent. The figure rises to 52 per cent in what has been termed the ‘intensive land use zone’ of the continent, which includes much of the MDB (Graetz et al. 1995). At least half of the Basin's pre-European vegetation cover has been removed. Many new plants and animals have replaced the native ones. Especially in the arid and semi-arid areas, many native species are not regenerating. Many species have been lost, not least those of the native grasslands. There is little wilderness of high quality remaining in the Murray-Darling Basin (AHC 1995). Australia has an unfortunate record of such flora and fauna losses, and many animals and plants remain on the endangered list. However, whilst much of the remaining natural vegetation is still at risk of being cleared, with very little left in some areas, an increasing proportion is now contained in managed reserves of one kind or another, though many of these remain vulnerable to future disturbance (Graetz et al 1995) (see National Parks and other Reserves). Of considerable importance are the remnant vegetation sites, small areas of native plant communities outside the boundaries of parks and reserves, that have remained relatively untouched. Many are small and unconnected, and insufficient to conserve the dependent fauna. For example, it is estimated that no more than 0.5 per cent of native grasslands are left in south-east Australia, with much of these being along roads, railway lines, stock routes, and in old cemeteries. Such remnants are under increasing pressure, in all kinds of locations, both rural and urban. They need to be conserved as much as the parks. In fact, what areas remain of the native grasslands are perhaps in greater need of protection than some forest areas. <Top of Page> |
