Reduction in Moreton Bay wetlands poses threat to fishing industry

23 Mar 2017

Mangroves moving into the marshMoreton Bay has lost 64 per cent of coastal tidal marshes since 1955, according to new research presented at a south-east Queensland forum.

The University of Queensland’s Professor Catherine Lovelock, who spoke at a recent Moreton Bay (Quandamooka) Catchment Forum said Queensland Herbarium research showed losses were largely due to alternative land uses, as marshes were drained and cleared.

Tidal marshes or salt marshes are regularly flooded by tides, and are dominated by salt-tolerant plants including herbs, grasses and low shrubs.

halloran saltmarsh and mangrove

“Mangroves, saltmarshes and seagrass wetlands are fish and seafood nurseries,” said Professor Lovelock, of UQ’s School of Biological Sciences and the Global Change Institute.

“Mangrove encroachment is a factor in these losses, and latest findings show there have been high losses of marine couch grass habitat.”

“While proximity to mangroves is important for fish communities in Moreton Bay, connected ecosystems such as tidal marshes provide important resources for terrestrial species such as kangaroos.”

Professor Lovelock said in the same period, there had been changes in mangroves due to clearing and gains due to colonising sediments and expansion into tidal marsh habitats. 

“Overall, there’s been a 6.7 per cent increase in mangrove cover in the Moreton Bay region since 1955,” she said.

Professor Lovelock said mangroves were important habitats for biodiversity, fisheries and flood protection.

“They retain nutrients and sediments, sequester carbon, and have other educational, recreational and cultural uses,” she said.

 “The seafood industry is the fifth largest primary industry in Queensland, with an annual commercial catch worth several hundred million dollars.

 “An estimated 75 per cent of fish and prawns caught in Queensland depend on mangroves or mangrove food chains sometimes in their lives.”

Professor Lovelock said mangroves and tidal marshes were important assets of Moreton Bay and their current distribution was protected by regulations and policies, and initiatives such as MangroveWatch, which uses a partnership between the community, volunteers and scientists.

“Mangroves are vulnerable to climate change and rising sea levels, so we need to plan landscapes to sustain wetlands that can support biodiversity of fisheries production in the future,” Professor Lovelock said.

She said researchers was monitoring the rates at which habitats were keeping up with current rates of sea level rise, and which were not, and therefore, vulnerable.

UQ, the Queensland Government, CSIRO, James Cook University, Griffith University and other researchers are studying the distribution of wetlands with future scenarios of sea level rise to support planning and management for resilient coasts.