Mangrove forest ecosystem fact sheet | Field of Mars EEC

What are mangrove forests?

Mangrove forests are intertidal ecosystems that grow along sheltered tidal rivers, creeks, bays and estuaries. They grow where land and water meet, in muddy or silty areas that are regularly covered by tides.

Mangrove forests are ecosystems because living things and non-living features interact. Living things include mangrove trees, algae, bacteria, fungi, crabs, molluscs, fish, insects, reptiles, birds and mammals. Non-living features include tides, salt water, mud, sediments, sunlight, air, nutrients and oxygen levels in the soil.

A habitat is a smaller place within an ecosystem where an organism lives and carries out activities. In a mangrove forest, habitats include mangrove roots, muddy flats, crab burrows, leaf litter, tidal channels, shallow pools and sheltered creek edges.

A mangrove forest.

Mangrove forests grow where tides regularly cover muddy estuary edges.

Where are mangrove forests found?

Mangrove forests are found in tropical, subtropical and some temperate coastal areas around the world. In Australia, they grow around much of the mainland coast, especially in sheltered estuaries, bays, tidal rivers and creeks.

In Sydney, mangrove forests grow along parts of the Lane Cove River, Parramatta River and Sydney Harbour estuary. They are part of the wider estuarine environment, where salt water from the ocean mixes with freshwater from rainfall, creeks and stormwater runoff.

Mangrove forests grow along sheltered tidal rivers and estuaries in Sydney.

What living and non-living features make up mangrove forests?

Mangrove forests include living things such as mangrove trees, algae, fungi, bacteria, crabs, molluscs, fish, insects, birds and other animals. Mangrove trees are producers because they use sunlight, water, air and nutrients to grow.

Non-living features shape where mangrove forests can survive. Tides bring salt water in and out of the forest, mud and sediments hold nutrients, and low oxygen levels in the muddy soil affect how mangrove roots grow. These conditions create smaller habitats such as mangrove roots, mudflats, crab burrows, leaf litter and tidal channels.

Mangrove roots and mud create habitats for crabs, molluscs, fish and other small animals.

What plants and animals live in mangrove forests?

Mangrove forests in the Lane Cove River and Parramatta River areas mainly contain grey mangroves and river mangroves. Grey mangroves have pencil-like breathing roots called pneumatophores that stick up from the mud and help the tree take in oxygen. River mangroves usually grow closer to the water’s edge and have bright green leaves with rounded tips.

Grey mangroves have pencil-like breathing roots that help them survive in oxygen-poor mud.

Many animals use mangrove forests for food, shelter and breeding habitat. Crabs feed on fallen mangrove leaves and other organic matter. Molluscs graze on algae and detritus. Fish use flooded mangrove roots as shelter, while birds such as cormorants, ibis, spoonbills and kingfishers feed in and around the mangroves. Decomposers such as fungi and bacteria help break down dead plant and animal matter.

Red-fingered marsh crabs live in muddy mangrove habitats and help recycle fallen leaves.

How do living things depend on mangrove forests?

Mangrove trees use sunlight, water, air and nutrients to grow. Their leaves, flowers, fruits, roots and fallen plant material provide food and habitat for many animals. A simple mangrove food chain could be: mangrove leaves and algae → crab or small fish → larger fish or waterbird.

Decomposers such as fungi and bacteria break down dead leaves, wood and animal remains. Crabs, worms, larvae and other small animals also help shred and move organic matter through the mud. This returns nutrients to the ecosystem and supports new plant growth, food chains and the wider estuary.

Fallen mangrove leaves, sticks, mud and crab burrows are part of the mangrove food chain.

How are mangrove forests important to Aboriginal Peoples?

Mangrove forests are part of wider coastal and estuarine Country that Aboriginal Peoples have long cared for, learned from and used. These environments can provide food such as fish, shellfish, crabs and other animals, as well as plant materials used for different purposes.

Public sources describe mangroves being used by Indigenous Australians as sources of food, and mangrove timber being used to make items such as canoes, paddles, shields, spears and boomerangs. Knowledge about plants, animals, seasons and places is held and shared by Aboriginal Peoples and should be treated with care.

Mangrove forests are part of estuary Country and have long supported food, materials and cultural knowledge.

Why are mangrove forests important?

Mangrove forests are important ecosystems for biodiversity. Their roots, branches, mud and leaf litter provide habitats for crabs, molluscs, fish, insects, spiders, reptiles, birds and mammals. Many young fish and crustaceans use mangrove roots as nursery habitat where they can feed and hide from predators.

Mangrove forests also protect estuary shorelines. Their roots help hold mud and sediment in place, reduce erosion, filter runoff, trap nutrients and buffer shorelines from waves and stormwater flows. Mangroves also store carbon in their wood, roots and muddy sediments.

Mangrove forests provide feeding and resting habitat for waterbirds such as cormorants.

What threats do mangrove forests face?

Mangrove forests can be affected by coastal development, land reclamation, changes to tidal flow, stormwater runoff, poor water quality, rubbish, chemical pollution, sedimentation and physical disturbance. Walking through soft mangrove mud can damage seedlings, roots, crab burrows and other small habitats.

Climate change can also affect mangrove forests through rising sea levels, changing water temperatures, altered rainfall and changes to estuary conditions. In some places, mangroves may move landward as sea levels rise, but roads, seawalls, development or other habitats can prevent this movement.

Sediment and changes in water quality can damage mangrove roots and cause dieback.

How can you help protect mangrove forests?

You can help protect mangrove forests by staying on boardwalks, tracks or firm edges, especially at low tide when mud, roots and crab burrows are exposed. Do not remove plants, animals, shells, rocks, logs, bark or mangrove seedlings.

Keep rubbish, chemicals, garden waste and soil out of drains, creeks and rivers. Stormwater can carry pollution into estuaries where mangroves grow. You can also learn about local estuary ecosystems, share accurate information, respect Aboriginal cultural knowledge and support bushcare or waterway care activities where appropriate.

Staying on boardwalks helps protect mangrove mud, seedlings, roots and crab burrows.

Related fact sheets

Environments and ecosystems

• Ecosystems and environments fact sheets – Explore more Field of Mars EEC fact sheets about local ecosystems, environments and habitats.
• Coastal salt marsh fact sheet – Learn about another intertidal ecosystem found beside estuaries, mudflats and mangrove forests.
• Field of Mars Reserve fact sheet – Find out about the wider local environment that includes bushland, creeks, wetlands, mangroves and salt marsh.
• Eucalypt forest fact sheet – Compare mangrove forests with a dry forest ecosystem found around Field of Mars Reserve.

Plants in this ecosystem

• Grey mangrove fact sheet – Learn about the main mangrove tree species found in many Sydney mangrove forests.

Animals in this ecosystem

• Red-fingered marsh crab fact sheet – Discover a small crab that feeds on mangrove leaves and helps recycle nutrients in the mud.
• Semaphore crab fact sheet – Learn about another crab that lives in soft mud near mangrove roots and tidal flats.
• Australian white ibis fact sheet – Explore a waterbird that may feed around wetlands, mudflats and estuary edges.
• White-bellied sea eagle fact sheet – Learn about a large bird of prey linked to waterways, wetlands, estuaries and coastal habitats.

Habitats and ecosystem processes

• Habitat fact sheet – Learn what habitats are and how they provide living things with food, shelter, water and space.
• Water habitats fact sheet – Explore water-based habitats used by animals in ponds, creeks, rivers, wetlands and other aquatic environments.
• Invertebrate fact sheets – Explore animals such as crabs, insects, spiders, molluscs and worms that help move energy and nutrients through ecosystems.
• Bird fact sheets – Learn about birds that use forests, wetlands, waterways and estuary habitats.

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