Mangroves

Some people don’t like mangroves, regarding them as muddy, mosquito and crocodile infested swamps. In the past their removal was seen as a sign of progress. So what is the point of preserving them? For a start, an estimated 75 percent of fish caught commercially spend some time in the mangroves or are dependent on food chains which can be traced back to these coastal forests.

Mangroves also protect the coast by absorbing the energy of storm driven waves and wind. The only two yachts undamaged by Cyclone Tracey in Darwin in 1974 had sheltered in a mangrove creek. While providing a buffer for the land on one side, mangroves also interact with the sea on the other. Sediments trapped by roots prevent silting of adjacent marine habitats where cloudy water might cause corals to die. In addition, mangrove plants and sediments have been shown to absorb pollution, including heavy metals.Worldwide, vast tracts of mangroves have been destroyed so we are lucky to have relatively large areas of Australia’s tallest and best-developed mangroves still existing on our doorstep.Now that their economic and ecological importance has been recognised we carry the responsibility to look after our mangroves.

A mangrove is a woody plant or plant community which lives between the sea and the land in areas which are inundated by tides. Thus a mangrove is a species as well as a community of plants. It can be a tree but (like a ‘rainforest plant’) it can also be a shrub or palm. All share the ability to live in salt water.

As a general rule zones of dominant mangrove species run parallel to the shoreline or to the banks of tidal creek systems. The seaward side of the community is likely to be dominated by a fringe of grey mangroves Avicennia marina as it is best adapted to early colonisation and a wide range of soil conditions. Avicennia marina is a tough mangrove species - Australia’s most widespread due to its ability to tolerate low temperatures and a variety of other intertidal conditions. A pioneer, it is likely to be the first species to grow on newly-emerged mud banks, putting up its distinctive peg roots. Mangrove apple Sonneratia alba often grows in this zone too, but it is a more tropical mangrove. The red mangrove Rhyzophora stylosa, also known as the stilt or spider mangrove, is usual...

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...ay a part in western medicine. Certain tree species, notably the cedar mangrove, cannonball mangrove (relatives of the red cedar) and the grey mangrove, are prized for their hard wood and used for boat building and cabinet timber as well as for tools such as digging sticks, spears and boomerangs. The fronds of the nypa palm are used for thatching and basket weaving. Various barks are used for tanning, pneumatophores (peg roots) make good fishing floats while the wood from yellow mangroves (Ceriops species) has a reputation for burning even when wet.

Worldwide there are about 65 recognised species of mangrove plants belonging to 20 families. Up to 35 mangrove species and three hybrids are known to occur in Queensland although figures can change as the definition of a mangrove is not clear and some plants such as cottonwood are regarded as mangrove by some and not by others. A study of Cairns mangroves found 24 mangrove tree and shrub species while a further 18 species of flowering plants were growing among the mangroves or on salt marshes. An additional 42 species of epiphytic plants and 25 species of fungi were identified growing on the mangroves.