Australian forest profiles: Melaleuca
There are hundreds of species in the genus Melaleuca and many other species in closely related genera, such as Callistemon. Classification of these species is being reviewed. When that review is completed, Melaleuca will likely contain 260 species or more, of which more than 220 are endemic to Australia. The remainder occur in New Caledonia, India, Indonesia, Malaysia, New Guinea and the Pacific Islands. Only a small number of these species develop the required community structure and height to be classified as forests.1
Although melaleuca forest makes up only 5% of Australia’s forest area, it is the third most extensive forest type after eucalypts and acacia. There are more than 7.5 million hectares in Australia, almost all being woodland and open forests (Table 1).
The word ‘melaleuca’ comes from the Greek melas (meaning black) and leucon (meaning white) and, when first coined, was probably a reference to the fact that some species have white bark over an inner layer of black bark, although it might also have referred to trees with white trunks and bases burnt black by fire, or to the black trunks and white branches of some Asian species. Another commonly used name for melaleuca is tea tree, although this is also applied to the closely related genus Leptospermum. It stems from the observation that shed leaves and bark can turn stream water the colour of tea. Some melaleucas are known as paperbarks because of their distinctive light, flaky bark.
Melaleuca forests occur mainly as large tracts of low woodland forest across estuarine plains and seasonal swamps in the coastal and near‑coastal areas of monsoonal northern Australia. They also occur as narrow strips of dense, pure stands beside streams and in and around swamps, although these ecologically important forests are often too small to be mapped at the national level.
Where are Australia’s melaleuca forests?
About 75% of Australia’s melaleuca forest occurs in Queensland, particularly on Cape York Peninsula (Table 2 and Figure 1). A further 22% is found in the northern part of the Northern Territory. Small pockets occur along the subtropical and temperate coasts of Queensland, New South Wales and Victoria, and on the fringes of rivers and coastal wetlands, including in brackish and saline areas. Extensive stands of swamp dominated by melaleucas, blackwood (Acacia melanoxylon) and Leptospermum species occur on poorly drained sites in northwestern Tasmania.
The dominant species in melaleuca forests vary markedly. Northern Australian melaleuca forests are dominated by broadleaved paperbark (Melaleuca viridiflora), weeping or long-leaved paperbark (M. leucadendra), silver paperbark (M. argentea), blue paperbark (M. dealbata) and yellow-barked paperbark (M. nervosa).
In southern and eastern Australia, melaleuca forests are confined to permanently wet watercourses and swamps. The most common coastal species is the paperbarked tea tree (M. quinquenervia). In Western Australia, melaleuca forests are restricted to small pockets on specific sites, such as Preiss’s paperbark (M. preissiana) in near-coastal swampy areas and freshwater or swamp paperbark (M. rhaphiophylla) along watercourses.
Source: National Forest Inventory, 2008.
Note: The resolution of forests shown on this map has been enhanced to ensure their distribution is visible at the national scale.
Ownership and management
Nationally, 72% of melaleuca forest occurs on leasehold land and 16% on private land (Table 2). In both cases, the main land use is grazing for cattle production. Only 8% of melaleuca forest is within nature conservation reserves, while about 2% is located in multiple-use public forest or on other Crown land.
Values and uses
Wood
Melaleuca wood contains a high proportion of silica, which makes it durable in both soil and water and highly resistant to termites. It also makes the wood difficult to mill and dry, so it is not widely used commercially. Logs of straighter trees are sometimes used locally for marine piling and in boat building.
Environmental
Even small areas of melaleuca forests can provide important habitat for a wide range of species. Swamp paperbark (Melaleuca ericifolia) in the Damper Creek Reserve in Monash, Victoria, for example, contains a diversity of habitats and is considered to be a site of regional zoological significance. Melaleuca forests provide habitat for the vulnerable southern bell frog (Litoria raniformis) and an assortment of other fauna.
Drainage and flood mitigation measures, taken mostly during the 1970s and 1980s, as well as increased waterlogging and salinity, particularly in irrigation areas, have affected melaleuca forests along creek lines and watercourses in many agricultural areas. Peat and other materials have been extracted from swamps for use in horticulture, further damaging such forests. Melalueca forests have also been cleared, including for sugarcane on the Herbert River floodplain in northern Queensland.
Indigenous uses
Indigenous people in parts of the Northern Territory traditionally use the bark of long-leaved paperbark for many purposes, including for sheaths to hold stone knives and spearheads, as tinder for starting fires, to cover baking food, as a component of fish traps, as a material for blankets or capes, and to make canoes. The flowers can be sucked for nectar or soaked in water to make a sweet drink.
Other uses
Plantations of some melaleucas, particularly Melaleuca alternifolia, supply the raw material for the tea tree oil industry. Tea tree oil is an effective antiseptic and is used in creams for cuts and abrasions, shampoos, soaps, mouthwashes and toothpastes. Paperbark is used in the horticultural industry as a lining for hanging baskets. Melaleuca flowers are important for apiarists as a food source for bees and are sometimes known as ‘honey myrtles’ for this reason.
Crocodile egg industry
Saltwater crocodile (Crocodylus porosus) eggs are often taken from melaleuca wetlands. The harvesting of saltwater crocodile eggs in the wild, largely by Indigenous Land and Sea Ranger groups on Indigenous lands, has been taking place in the Northern Territory since 1984, when the controlled international trade of the species and of products derived from it was legalised.
Harvested eggs are hatched in farms. The crocodiles are grown to the desired market size and then used for skin and meat production.
Tea tree oil industry
The indigenous Bundjalung people of eastern Australia use tea trees in traditional medicine. They inhale the oil from crushed leaves to treat coughs and colds. Leaves are sprinkled on wounds and also soaked in water to make an infusion for treating sore throats and skin ailments.
The commercial tea tree oil industry came into being after the medicinal properties of the oil were demonstrated in the 1920s. When applied topically, the anti-microbial activity of tea tree oil was rated 11 times more active than phenol. The oil was produced from foliage collected from natural stands of Melaleuca alternifolia. The plant material was hand-cut and often distilled in the forest in makeshift, mobile, wood-fired bush stills. Production declined after World War II but was revived in the 1970s as part of the general resurgence of interest in natural and organic products. Many small operators collected foliage from both the wild and a large number of small plantations to meet demand.
In the 1970s and 1980s some 6 000 hectares of Melaleuca alternifolia plantations were established and mechanisation enabled the large-scale production of a consistent essential oil product. The ingredient active in most of the antimicrobial actions of tea tree oil is terpinen- 4-ol, which is now defined by an international standard.
A wide range of tea tree oil-based medical and cosmetic products is now available.
References and further reading
Baskorowati L (2006). Controlled Pollination Methods for Melaleuca alternifolia (Maiden & Betche) Cheel. ACIAR Technical Report No. 63, Australian Centre for International Agricultural Research, Canberra.
Boland D, Brooker M, Chippendale G, Hall N, Hyland B, Johnston R, Kleinig D, McDonald M and Turner J (2006). Forest Trees of Australia, 5th edition, CSIRO Publishing, Melbourne.
Doran J, Baker G, Williams E and Southwell I (2002). Improving Australian Tea Tree, Report for the Rural Industries Research and Development Corporation, Canberra.
MIG (Montreal Process Implementation Group for Australia) (2008). Australia’s State of the Forests Report 2008, Bureau of Rural Sciences, Canberra.
NFI (National Forest Inventory) (2003). Australia’s State of the Forests Report 2003, Bureau of Rural Sciences, Canberra.
Footnote
Australia’s definition of forest is ‘an area dominated by trees having usually a single stem and a mature or potentially mature height exceeding 2 m and with an existing or potential crown cover of overstorey about equal or greater than 20%.’