Species Focus - Mangrove

Mangroves (Avecinnia marina) are one of the few true plants that can make a life in the sea, as algae are not a true vascular plant.

They’re an estuarine species tolerant of a wide range of conditions, including hyper salinity which is achieved partly by excreting salt through their leaves, and they thrive even more when the water is more brackish. Being so affected by both tides and fluvial input, their habitat is also usually hypoxic, and to counteract this mangroves have aerial roots, called pneumatophores which permit them to absorb atmospheric oxygen.
The species is also a resource for many people in the various regions of the world where they grow. For instance, the strong, even-textured wood is used extensively as materials for housing and boats, and as fuel for fires and kilns. Near the Red Sea the leaves are used as camel fodder; in Australia its branches are fed to cattle, and the bark is widely used as a brown dye.

Even more intriguing is its use in medicine. There are tales that the root and bark are used as an aphrodisiac, and with parts of the wood also used to treat snakebite! More credible is that the juice from the seeds and leaves can be made into a poultice to treat sores and wounds.

Mangroves are a pioneer species adept at colonising new territories. Their iconic green floating, salt-tolerant seedlings can disperse far and wide along ocean currents which is an attribute that has led to their disfavour among some, when an area once a sandy embayment, or with shellfish-harvestable mudflats, becomes quickly overgrown by fields of mangroves. However, when this occurs it is usually as a result of prior human interference in a waterway, for instance when a causeway is built across the arm of an estuary.

More importantly, their ability to rapidly colonise an area, and their strong resilience means mangroves are hugely beneficial for the environment and for human habitation since they provide food and shelter for many species, and act as nurseries for fish species. They also protect the shoreline from ever increasing storm surges and wave action.

All in all, mangroves are a hardy species of integral importance for the health of our estuaries.

Fast Facts

Fast Facts1. An estuarine species of tree, tolerant of hypersaline conditions.
2. Native to northern New Zealand and with a large global distribution.
3. A pioneer species that can form on muddy/sandy habitats.
4. Its Māori name is mānawa.
5. It has aerial roots (pneumatophores), allowing the plant to absorb oxygen.
6. Very effective at sequestering atmospheric carbon, known as ‘blue carbon”.
7. Act as nursery habitats for many species.
8. Have great dispersal abilities, with seed pods moving by sea.