Restored wetland. Credit: RMIT
A study of floodplain wetlands in southeastern Australia has shown that restoration of these unique ecosystems can significantly boost natural carbon storage and drought resilience.
Wetlands support high biodiversity and are under increased threat due to human-induced climate change, habitat destruction and pollution. Roughly one-fifth of wetlands – 3.4 square kilometres – are estimated to have been lost globally over the past 300 years.
Wetlands are also well-known natural carbon sinks where greenhouse gases like carbon dioxide from the atmosphere can be absorbed. A recent study, for example, showed that Southeast Asia’s peatlands and mangroves could mitigate more than 50% of the region’s land-use carbon emissions.
While these natural habitats should be conserved, not all wetlands are created equal when it comes to carbon storage.
Degraded wetland. Credit: RMIT
Peatlands are characterised by heaps of decayed plant matter, forming peat soil which under intense pressure and heat over millions of years becomes coal. This spongey material is a great carbon store. But some studies suggest that restored peatlands could release up to 530% more methane than degraded ones, possibly mitigating any short-term carbon storage by this type of wetland.
Restored floodplain wetlands, however, show promise as long-term carbon stores, according to a new study published in the Journal of Environmental Management.
Floodplain wetlands are areas next to rivers that are periodically inundated with floodwaters. They make up about half of global wetlands but are often overlooked as carbon sinks due to their lower storage.
The findings of the research led by scientists at RMIT University in Melbourne suggest that restored floodplain wetlands reduced local carbon emissions by 39% within just 1 year. Unrestored wetlands increased net carbon emissions by 169% in the same period.
One floodplain wetland had 53% more carbon stored 6 years after being restored.
“Restoring wetlands could be a secret weapon against climate change,” says Lukas Schuster from RMIT’s Centre for Nature Positive Solutions. “We found managing freshwater wetlands for carbon benefits also boosts flood and drought resilience, highlighting the dual benefits of restoration.”
Rewetting and revegetation restoration works led to an increase in soil moisture of 55%, even after the wetlands themselves had dried after floods.
Researchers collecting samples from restored wetland. Credit: RMIT
“We observed a vital link between carbon dynamics and ecosystem function,” Schuster says. “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 quickly their recovery can be, it’s time to act.”
Schuster’s team compared 3 degraded wetlands with 3 restored wetlands along the Loddon River in the north of Australian state Victoria. Native plant cover in the restored wetlands also increased significantly, and these native plants showed a greater potential for carbon storage in the soil than invasive grass species.
Restored wetlands had also absorbed 45% more nitrogen in the soil.
“More nitrogen removed from these wetlands has a positive flow-on effect to connected waterways,” Schuster adds. “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.”