Territory Environments

• Mangrove Management in the NT 2002 report
• Mangrove Education Kit

Mangroves

Mangroves (or more correctly mangal forests) are a distinctive vegetation type occupying the intertidal areas of much of the Northern Territory coast and lower reaches of many rivers. The Northern Territory includes some of the world's most extensive and diverse mangrove associations. Much of the ecology of mangrove areas is dictated by the pattern of tidal movement. For example, there is typically a well-defined zonation of dominant plant species from the tall white mangrove Sonneratia alba on the seaward side through to the smaller Ceriops tagal on the landward side. Other distinctive mangrove plants include the stilt-rooted mangrove Rhizophora stylosa, which produces a maze of arching stilt roots from the trunk and slender aerial roots from branches, the cannonball mangrove Xylocarpus australasicus, which bears large 'monkey-puzzle' fruits, the mangrove fern Acrostichum speciosum and the mangrove palm Nypa fruticans. However, mangrove formations typically have relatively low plant species diversity, and only about 25 tree species and 25 other plant species are closely associated with mangrove formations in the Northern Territory.

Mangroves support a highly specialised fauna, including many species which occur nowhere else. Distinctive mangrove birds include the yellow white-eye Zosterops lutea, chestnut rail Eulabeornis castaneoventris, black butcherbird Cracticus quoyi, mangrove gerygone Gerygone levigaster, mangrove robin Eopsaltria pulverulenta, white-breasted whistler Pachycephala lanioides, and mangrove golden whistler Pachycephala melanura. Other distinctive mangrove fauna includes the false water-rat Xeromys myoides, mangrove monitor Varanus indicus and a group of colubrid snakes including the white-bellied mangrove snake Fordonia leucobalia, the bockadam Cerberus rhynchops and Myron richardsonii. Mangroves are also very important as nursery sites for many fish species and for the commercially important delicacy, mangrove crabs.

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Total area

The total extent of mangrove forests in the Northern Territory is 1,440 km2, spread in a narrow band across much of the Top End coastline.

Mangal forests of the NT (Red: extracted from Wilson et. al. 1:1M Vegetation Map and Green: extracted from Brocklehurst et. al. Mangroves of the NT Coast)

Presence in conservation reserves

About 8% of the extent of Northern Territory mangroves is included within the conservation reserve system. At a mapping scale of 1:1,000,000, mangroves are shown to occur in four parks: Channel Island Conservation Reserve, Garig Gunak Barlu National Park, Kakadu National Park and the Territory Wildlife Park/Berry Springs Nature Park. Mangroves also occur in Charles Darwin National Park, Casuarina Coastal Reserve, Djukbinj and Indian Island Conservation Area. Elevated walkways at Channel Island and East Point Reserve provide good means of access to mangroves near Darwin: other good areas to visit mangroves include Casuarina Coastal Reserve and Charles Darwin National Park.

Threats

Most of the Territory mangrove formations remain in good condition. Mangroves close to major developments and population centre have suffered some clearing and localised damage from contaminants. Mangrove Communities of the Darwin Harbour were the subject of a comprehensive report completed in 1996. This work has now been extended to Bynoe Harbour and an area from Lee Point to Adelaide River. Riverside mangroves may be vulnerable to attempts to exploit water by damming. Historically, the extent of mangroves in the Northern Territory has fluctuated substantially in response to changes in sea level; and further periods of changes in sea levels may lead to pronounced changes in distribution.

Although there are some threatened species recorded from mangal forests there are none that occur primarily in mangroves.

Further reading

• Noske, R.A. (1996). Abundance, zonation and foraging ecology of birds in mangroves of Darwin Harbour, Northern Territory. Wildlife Research 23, 443-474.
• Wightman, G.M. (1989). Mangroves of the Northern Territory. Northern Territory Botanical Bulletin no.7. (Conservation Commission of the Northern Territory: Darwin.)

Mangrove Management in the Northern Territory 2002 report

• In full pdf 5.9Mb

Sections

• Front cover (pdf 233Kb)
• Contents and Forward (pdf 50Kb)
• 1 - Introduction (pdf 333Kb)
• 2 - The Mangrove Ecosystem (pdf 544Kb)
• 3 - Current State of Knowledge (pdf 719Kb)
• 4 - Management of the mangrove resource (pdf 424Kb)
• Glossary, References, and Internet sites on Mangroves (pdf 49Kb)

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