Wetlands as coastal protectors

Wetland provide key ecosystem services including protecting and stabilising shorelines, regulating floods, supporting fisheries, improving water quality, storing carbon, and acting as habitats for a diverse range of species.

The Great Barrier Reef catchment has lost a significant area of wetlands over the past 200 years, with those remaining continuing to face a range of threats. This includes sea level rise, severe storms, coastal erosion and impacts from human activities, which affect health, resilience, and reduce biodiversity.

While maintaining the health of existing wetlands is crucial, scoping potential sites for restoration is also an important step. 

Our scientists explored restoration opportunities in two ways: identifying sites where freshwater and intertidal wetlands, including mangrove and saltmarsh, could be restored, and scoping the environmental suitability of water-tolerant trees at potential sites to support diverse restorations.

Finding restoration opportunities for water-tolerant trees

This project investigated potential areas for wetland restoration across the Great Barrier Reef Catchment. The research screened over 120 water-tolerant trees for their environmental suitability to identify potential sites. 

By identifying the best-suited species for these areas, we can enhance restoration efforts. Planting multiple species in initial wetland restoration, instead of a monoculture, better supports the establishment of diverse and healthy ecological communities.

Over 2,200 land parcels were identified, covering over 20,000 hectares across the Great Barrier Reef catchment, with numerous species being suitable for all sites.

The team used the following methods:

• Extracted data on water-tolerant tree species and distribution, climate, water inundation frequency, and soil attributes from databases.

• Used machine learning to predict the likelihood of water-tolerant trees occurring at each location based on climate, water, and soil characteristics.

• Applied this modelling to locations of former wetlands across the Great Barrier Reef catchment to identify the suitability of different species for potential restoration at each location.

Identifying potential sites for mangrove and saltmarsh restoration

The team investigated locations between Cairns and Gladstone for potential mangrove or saltmarsh restoration to increase carbon sequestration and storage. They identified around 17,255 hectares of coastal land for restoration, across 52 potential restoration sites.

The team identified potential sites for restoration using:

• High-resolution photography from low-flying helicopters to capture overlapping, georeferenced images of shorelines.

• Evaluation of potential areas using measures such as tidal inundation mapping, digital elevation models, long-term changes in mangrove health, and land parcel tenure status.

The team also identified likely risks for each potential restoration project, and dominant drivers of change including pollutant impact, access tracks, shoreline erosion, and storm damage.

Future steps: carbon benefits and maintaining wetlands

Carbon sequestration programs such as the Australian Government’s Emissions Reduction Fund and Blue Carbon program could offer new opportunities for wetland restoration. But this requires identifying areas where interventions can yield tangible and measurable carbon benefits.

While the studies identified multiple locations for potential restoration – for both freshwater and intertidal wetlands – they emphasise that effective and lasting restoration can be challenging to achieve.

Monitoring and maintaining the health of wetlands and coastal habitats is the best way to ensure carbon storage benefits and maintain biodiversity. This is especially true as degradation continues to impact these vital ecosystems along the coast.

Project details

These projects were led by Dr Adam Canning and Professor Norman Duke and were funded by Greening Australia for its Reef Aid program.