Freshwater wetlands cover less than ten per cent of the Earth’s surface yet they contribute up to 25 per cent of global methane emissions. Despite this, they hold significant potential as long-term carbon sinks, playing a crucial role in the global carbon cycle.
New research has confirmed the importance of rehabilitating floodplain wetlands and riparian wetlands – not just for the impact they have on climate change but also water quality, flood and drought-resilience outcomes.
The new study found that restored wetlands provide benefits for climate and drought-resilience after just one year. Reviving floodplain wetlands slashes carbon emissions by 39 per cent and restores critical ecosystem functions in the first year – without the methane spike typically seen in restored peatlands.
Peatlands are known as top carbon sinks, but can produce up to 530 per cent more methane after restoration, potentially offsetting short-term climate benefits. Whereas floodplain, or riparian wetlands, which comprise over half of global wetlands, are often overlooked due to their lower carbon storage.
Quick action needed
Study lead-author Dr Lukas Schuster from RMIT University’s Centre for Nature Positive Solutions said the scale and pace of ecosystem benefits revealed within just one year of restoration provide a clear case for action.
‘Restoring wetlands could be a secret weapon against climate change,’ he said.
‘We found managing freshwater wetlands for carbon benefits also boosts flood and drought resilience, highlighting the dual benefits of restoration.’
While rewetting and revegetation reduced carbon emissions by 39 per cent, net carbon emissions from the unrestored control wetlands increased by 169 per cent over the monitoring period.
Surface organic carbon stocks, where carbon is stored in plant roots and soil, increased by 12 per cent within one year in restored sites and decreased by ten per cent in control sites, showing the difference in carbon sequestration potential.
Restored wetlands retained more water in the area, with soil moisture levels increasing by 55 per cent, even after the wetlands themselves had dried, showing drought mitigation potential.
Schuster said increased water retention was linked to improved surface carbon storage in freshwater wetlands.
‘We observed a vital link between carbon dynamics and ecosystem function,’ he said.
Nature’s purification system
‘Wetlands are nature’s purification system, removing nitrogen from waterways and carbon from the atmosphere.
‘Now we know even more about the important role they play and how quick their recovery can be, it’s time to act.’
For the study, researchers compared three degraded, with three restored, wetlands along the Loddon River in Victoria, measuring native plant cover, carbon cycling and ecosystem function.
In the restored wetlands, native plant cover increased significantly, with leaf litter from two dominant native wetland species decomposing more slowly than that of an invasive grass species, suggesting a greater potential for carbon preservation in the soil.
With 45 per cent more nitrogen retained in the soil, restored wetlands showed increased nutrient cycling, which is linked to improved water quality and helps prevent ecosystem disruption like harmful algal blooms, oxygen depletion, and contamination.
Schuster said this was important because riparian wetlands are connected to other ecosystems like rivers and streams.
‘More nitrogen removed from these wetlands has a positive flow-on effect to connected waterways,’ he said.
‘If you manage the carbon outcome, you get other benefits like drought resilience and healthier farmland where flora and fauna can thrive. We’ve shown wetland restoration pays off, so we hope this study will inform future land management policies.’
A floodplain wetland was also monitored six years after it was restored by reintroducing water flow, finding surface organic carbon stocks increased by 53 per cent, demonstrating lasting benefits.
Fish kills
It’s estimated that approximately 50 per cent of all wetlands in NSW have been lost since 1788, with some areas experiencing losses as high as 70 to 90 per of low-lying wetlands, according to estimates from the NSW Department of Primary Industries and the Nature Conservation Council of NSW. So rather than filling, then farming, or building on our wetlands perhaps a new, scientific approach is needed.
The Richmond and Clarence rivers and catchments have seen significant impacts after the loss of wetlands and riparian wetlands with recorded increases in acid sulfate soil discharge that has a significant impact on water quality and contributes to the ongoing fish kills and blue-green algae blooms.
‘The Tuckean Swamp is one of the most important wetland systems in the Richmond catchment,’ explained Ray Klerck, President of OzFish Richmond River Chapter.
‘This research confirms what many of us already knew about the importance of restoring wetlands like the Tuckean. They don’t just help fish and birds, they fight climate change, cut emissions, and build resilience against drought and floods.
‘For a river system like the Richmond, which has suffered from fish kills and poor water quality, this is a clear call to action. Luckily, the science shows recovery can start within a year, all we have to do is help nature do its thing by righting the mistakes of the past.’
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