Mangrove Typologies in Mauritius

Why Typologies Matter

Classifying mangroves by typology helps improve conservation and management. A small estuarine mangrove patch may be highly important for fish nursery habitat and sediment trapping. A narrow lagoon-fringe stand may be critical for shoreline protection. A restored site may need survival monitoring rather than simple area mapping. An islet mangal may be small but highly vulnerable to storms and sea-level rise.

For this reason, the Mauritius Mangrove Atlas should not be interpreted only as a map of mangrove area. It is also a functional ecological baseline. Each mapped polygon should be understood in relation to its setting, condition, pressures and management needs.

This typology-based approach supports:

• Environmental Impact Assessment and coastal permitting

• Restoration planning and site selection

• Blue carbon monitoring

• Post-cyclone and post-disturbance assessment

• Protection of nursery habitats and lagoon connectivity

• Long-term national mangrove monitoring

1. Estuarine Mouth Systems

Estuarine mouth mangroves occur near river mouths, stream outlets and coastal channels where freshwater and seawater mix. These sites are usually influenced by tidal movement, brackish water, fine sediment deposition and periodic flooding.

In Mauritius, estuarine mangroves are important because they help trap sediments and nutrients before they enter the lagoon. Their root systems stabilise soft substrates and provide sheltered habitat for juvenile fish, crabs and other aquatic organisms. They also contribute to flood buffering and coastal resilience where rivers meet the sea.

Representative atlas setting: Ferney and other estuarine or river-mouth mangrove systems.

Main ecological functions:

Sediment and nutrient trapping
Fish and crustacean nursery habitat
Flood and storm-surge buffering
Water-quality regulation
Connectivity between rivers, wetlands, lagoons and reefs

Main risks:

Upstream pollution
Altered freshwater flow
Dredging or channel modification
Flood disturbance
Coastal development near river mouths

2. Lagoon-Fringe Systems

Lagoon-fringe mangroves occur as narrow belts or patches along protected lagoon shorelines. They are often found behind reef systems, along sheltered coastal margins and in low-energy areas where waves are reduced by the reef-lagoon system.

These mangroves are among the most visible forms in Mauritius. They often occur as linear or banded stands of Rhizophora mucronata, with dense prop roots extending into shallow water. Even when narrow, lagoon-fringe mangroves can provide important shoreline stabilisation, wave attenuation, sediment retention and habitat corridors.

Representative atlas setting: Poudre d’Or and other sheltered lagoon-margin sites.

Main ecological functions:

Shoreline stabilisation
Wave-energy reduction
Habitat corridors along the lagoon edge
Sediment retention
Support for reef-lagoon ecological connectivity

Main risks:

Coastal development
Shoreline hardening
Boat-access cuts
Trampling and pruning
Clearing for sea views or access

3. Hypersaline and Saltpan-Associated Systems

Hypersaline or saltpan-associated mangroves occur in restricted coastal settings where water circulation is limited and evaporation can increase salinity. These areas may include saltpans, back-reef depressions, poorly flushed coastal basins or low-lying areas where waterlogging and salinity stress influence mangrove growth.

These systems may appear sparse, stressed or structurally different from more open lagoon-fringe or estuarine mangroves. However, they are ecologically important because they represent stress-tolerant mangrove habitats. Their sediments may also contribute to long-term organic carbon storage where waterlogged conditions favour carbon accumulation.

Representative atlas setting: Petite Rivière Noire and other restricted or saltpan-associated coastal settings.

Main ecological functions:

Stress-tolerant mangrove habitat
Sediment stabilisation
Potential sediment carbon storage
Support for specialised coastal wetland conditions
Buffering of low-lying coastal margins

Main risks:

Hydrological modification
Infilling and reclamation
Saltpan alteration
Restricted tidal flushing
Conversion pressure

4. Island and Islet Mangals

Island and islet mangals occur around small lagoonal islands, islets and sheltered coastal features. These mangroves often develop in areas with limited freshwater input but sufficient tidal exchange and protection from strong wave energy.

In Mauritius, island and islet mangals are particularly important because they help stabilise low-lying islets, protect shorelines from erosion and provide refuge habitat within the lagoon. Their location also makes them vulnerable to storm overwash, erosion, sea-level rise and concentrated human disturbance.

Representative atlas setting: Île d’Ambre and other mangrove-bearing islets.

Main ecological functions:

Protection of low-lying islet shorelines
Refuge habitat for fish and invertebrates
Juvenile fish shelter
Sediment retention around islets
Contribution to lagoon biodiversity

Main risks:

Storm overwash
Erosion
Sea-level rise
Invasive species
Tourism and recreational pressure
Concentrated human disturbance

5. Restored Stands

Restored mangrove stands are areas where mangroves have been planted or actively managed. These sites may show even-aged cohorts, planting rows, protective structures or other signs of restoration intervention.

Restored stands are important for evaluating nature-based solutions in Mauritius. However, their success should not be measured only by the number of seedlings planted. Long-term monitoring is needed to assess survival, growth, canopy development, sediment stability, tidal suitability and ecological function.

Representative atlas setting: Le Morne, Case Noyale, Quatre Soeurs and Grande Rivière Nord Ouest, where restoration or planting has been recorded.

Main ecological functions:

Restoration of degraded coastal habitat
Canopy development and shoreline stabilisation
Future blue carbon gain tracking
Testing of nature-based coastal protection
Public education and community engagement

Main risks:

Poor site selection
Unsuitable hydrology
Low seedling survival
Inadequate maintenance
Lack of long-term monitoring
Planting success being overestimated from seedling numbers alone