Adaptations to
The tidal Zone

Australia’s mangroves show remarkable adaptations dealing with frequent saltwater inundation and varying climatic zones from arid to very wet. Mangroves share specialised attributes for growing with excess salt and saturated air-less soils. They also have special growth strategies to facilitate establishment and regeneration. One special attribute promoting sustainability and dispersal of mangroves is their unusual production of live young - vivipary. Such attributes have kept mangroves from extinction for more than 50 million years, and enabled them to occupy tidal areas around the world.

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Mangroves Defined

Nypa frucitans

Mangroves Defined

A mangrove is a tree, shrub, palm or ground fern, generally exceeding one half metre in height, that normally grows above mean sea level in the intertidal zone of marine coastal environments and estuarine margins. A mangrove is also the tidal habitat comprising such trees and shrubs.

The word ‘mangrove’ refers to the habitat in the same way as we think of ‘rainforest’ with its mixture of plant types. Sometimes the habitat is called a ‘tidal forest’ or a ‘mangrove forest’ to distinguish it from the trees that are also called mangroves.

Mangroves and others

Mangrove plants are not a single genetic entity because the plant types represented in the tidal zone are not all closely related. So, while they sometimes look the same, and have similar function, this tells us more about the environment they live in, rather than their family relationships. The plants growing in the tidal zone also require serious adaptations for their continued survival in this habitat. However, this does not preclude other plants from occasionally being found within the tidal zone. Some are grouped as ‘associates’ where they only occasionally occur in intertidal sediments and most of the time they are found elsewhere. Others do regularly also share the tidal niche, like saltmarsh plants, but these are smaller in size. A number of others, the epiphytes and plant parasites, perch in the branches and stems of mangroves. All these plants shape and define mangrove habitat.

Left - Nypa fruticans, the mangrove palm.

  • Daintree Rhizophora A tall stand of Rhizophora and Bruguiera trees in the Daintree River, Queensland.
  • Avicennia Marina Sea edge fringing small trees of Avicennia marina surrounded by numerous pneumatophores, Phillip Island, Western Port Bay, Victoria.
Daintree mangroves

Biologically Rich and Diverse

Australia’s mangroves have the fourth highest species diversity of any country, after the Philippines, Indonesia and Papua New Guinea. Most species in Australia occur widely throughout the Indo-West Pacific region. However, one species, Avicennia integra, is found only in Australia. Furthermore, a number of additional mangrove species and hybrids are more common in Australia than elsewhere in the world. Such notable biodiversity features help define the special characteristics that make Australia’s mangroves unique.

Australia’s mangroves consist of 22 genera from 19 plant families and there are 41 species. This represents 57% of mangrove species in the world. The areas of most abundance occur along the wet tropical coast of northern and eastern Australia. Many of these species furthermore come from a diverse range of plant families. And, these families belong to two major plant divisions, including one from the fern family the Polypodiophyta, and the remainder from the Magnoliophyta.

The latter are known also as the angiosperms or flowering plants. Just one family is exclusively mangrove – the Avicenniaceae Miq. in Lehm (1845). This is unusual since most families include only one or two mangroves. It is of further interest that even the Rhizophoraceae, the so-called ‘true mangrove family’, has only four of its sixteen genera represented in the tidal wetland habitat. Generally, the nominal ‘mangrove families’ are more commonly known for their upland habitat representatives especially those within tropical rainforests.

Right - a common association upstream are Acanthus ilicifolius thickets beneath an open canopy of Sonneratia caseolaris.

  • Heritiera littoralis A magnificient primal forest of Heritiera littoralis and Bruguiera gymnorhiza, Daintree River, Queensland.
  • Pemphis acidula Shrubby bushes of Pemphis acidula inhabit coral outcrops and coral beaches of the north.

Community Volunteers

A key feature of MangroveWatch is its close partnership between community volunteers and scientists from the James Cook University’s Mangrove Hub. Together they are systematically recording basic data as video and still imagery for assessments of estuarine habitat health.

Armed with expert support, training and advice, MangroveWatch volunteers in key regions are actively contributing to the monitoring of local estuaries and shorelines. An important goal in this phase of the program is to develop a network of like minded groups with the aim of producing public documents that describe important issues affecting local estuaries and mangroves, and their overall health.

Getting Involved

If you would like to find out more about us or if you like to initiate your own MangroveWatch group within your area, please contact someone at the Mangrove Hub. We will be happy to help.

  • Mangrove Hub Facilitator
  • Dr Norm Duke
  • MangroveWatch Ltd
    ABN: 44 153 297 771
  • PO Box 1250,
  • Elanora Q 4221
  • Mangrove Hub Email

Mangrove Watch Brochure

You can download our fact and information sheet (see link below) to get more information about the MangroveWatch programs.

Mangrove Watch Brochure