Wetlands under fire: How did the black summer bushfires impact estuarine wetlands?

A new study detailing the impact of the black summer 2019/20 fires on estuarine wetlands has just been released.

The study looks at the unprecedented burning of both mangrove forests and saltmarsh during these fires and ways we can look after these vulnerable ecosystems into the future.

Mangroves, unlike eucalypt forests, are not adapted to survive fire. As a result, areas burnt during the fires remain barren even three years after the fires went through.

DPI Fisheries Scientist Daniel Swadling said that the study was critical so we can look after these vulnerable ecosystems into the future.

“It is important to quantify these impacts to mangroves. Given that the climate is warming, fires such as these are likely to become more frequent,” he said.

He said that although relatively small areas of mangroves burnt, the effect on the mangroves areas was devastating.

“For instance, on the Clyde River, we found that three years after the fires, the burnt mangrove areas are still dead and there was minimal recruitment of new plants in many areas.”

“Mangroves are important for estuaries, as they act as fish habitat and nurseries, store carbon and protect our shores from erosion. Given this, it’s important to protect mangroves from fires in the future,” he said.

Using satellite imagery and ground truthing, the study found that substantial areas of estuarine wetlands burned; with 183 ha of saltmarsh and 23 ha of mangrove burning in 19 estuaries across the state, from Richmond River to Wonboyn Lake.

The worst hit estuary for mangroves was Clyde River on the south coast (14 ha), whilst Lake Cathie (60 ha), Wonboyn Lake (42 ha) and Manning River (30 ha) were the largest areas of saltmarsh burnt during the fires.

Dr Swadling said research also examined what factors increase the likelihood of mangroves burning.

“Mangroves were more likely burnt adjacent to wet sclerophyll forests. This impacts management, potentially helping to target areas for hazard reduction burning to reduce the chances of mangroves being burnt by future fire events.”

This research, conducted by DPI Fisheries, is part of the work to better understand, adapt, and help mitigate the impacts of climate change on the NSW coast funded under NSW Marine Estate Management Strategy.

To find out more, you can check out the research paper published in Ecological Management and Restoration here:
https://onlinelibrary.wiley.com/doi/full/10.1111/emr.12572