Mangroves and associated communities of Moreton Bay

Intertidal ecosystems, including mangrove and saltmarsh communities, provide significant social, cultural, economic and ecological values.

While these communities are currently protected under legislation, they are vulnerable to impacts from coastal development as well as from changes to natural processes such as siltation, nutrient runoff and climate.

Mangrove communities have increased in area by 1,213 ha (8.6%) between 1955 and 2016 whereas saltmarsh communities (including samphire, marine couch and claypan) have lost 6,000 ha (65.7%) of their 1955 extent. Casuarina glauca communities have lost 482 ha (31.8%) of their area during the same period. The spatial extent of each mangrove and associated community are described for the period from 1955 to 2016. While these communities are all dynamic in nature, losses due to anthropogenic causes have also occurred mainly from urban and infrastructure development.

Table 1. Mangrove, Saltmarsh, Casuarina glauca and Associated Communities extent over time

Changes in extent of mangrove communities from 1955 to 2016

• 10,901 ha were stable
• 3,150 ha either changed to another community type or were lost due to anthropogenic causes
• 4,343 ha were gained as a result of encroachment
• some mangrove community types have increased in area where others have decreased in extent
• 1,213 ha overall net gain of mangroves
• mangrove encroachment into saltmarsh and Casuarina glauca communities was 2,995 ha in the 1955 - 1997 period in comparison to 671 ha and 59 ha in the period 1997-2012 and 2012-2016 respectively.

Changes in extent of mangrove communities from 2012 to 2016

• During the period 2012-2016 there was net loss of 48 ha of mangrove communities in Moreton Bay. That is 107 ha loss of mangrove communities (94%) losses due to anthropogenic causes including the construction of the new airport runway in Brisbane City government area 92% and to roads works 2% in Brisbane City and Gold Coast local government areas. Mangrove losses due to change to other community type such as: free standing water – saline and brackish community 4%, saltmarsh communities 3% and Casuarina glauca communities 0.1%.
• During this period 59 ha of mangrove communities were gained by encroachment into: saltmarsh communities 59%; free standing water – saline and brackish community 22%; Casuarina glauca communities 8%; and other 11%. These mangrove communities gained by encroachment into other communities occurred in the Brisbane City 50%, Gold Coast 25%, and Moreton Bay Regional 16%.

Changes in extent of saltmarsh communities including samphire, marine couch and claypan from 1955 to 2016

• Moreton Bay saltmarsh communities are part of the subtropical and temperate coastal saltmarsh ecological communities that are listed as vulnerable under the Commonwealth EPBC Act 1999
• 2,608 ha were stable
• 6,629 ha either changed to another community type or were lost due to anthropogenic causes
• 560 ha were gained by dieback of other community types
• there was a large decrease across all the saltmarsh community types
• 6,000 ha overall net loss
• saltmarsh community invasion by mangrove and Casuarina glauca communities was 3,200 ha in the 1955–1997 period in comparison to 1,003 ha and 41 ha in the period 1997-2012 and 2012–2016 respectively.

Changes in extent of saltmarsh communities including samphire, marine couch and claypan from 2012 to 2016

• During the period 2012-2016 there was 47 ha loss and 14 ha gain leading to a net loss of 33 ha of Saltmarsh communities in Moreton Bay. That is 57% loss due to mangrove communities’ encroachment; 15% by encroachment of Casuarina glauca communities; 4% as a result of ponding and changing to free standing water – saline and brackish community and 2% losses due to anthropogenic causes including: airport and roads mainly in the Brisbane City 42%, Gold Coast 28% and Moreton Bay Regional 26% local government areas.
• 14 ha of saltmarsh community gain were as a result of encroachment: mangrove communities 25%, Casuarina glauca communities 22%, free standing water – saline and brackish community 21% and other 10%.

Changes in extent of Casuarina glauca communities from 1955 to 2016

• Moreton Bay Casuarina glauca communities are listed as Endangered under the Commonwealth EPBC Act 1999 as part of the Forest of New South Wales and South East Queensland ecological communities
• 925 ha were stable
• 1,214 ha either changed to another community type or lost due to anthropogenic causes
• 740 ha were gained by encroachment
• some Casuarina glauca communities have decreased in area where others increased
• 464 ha overall net loss
• Casuarina glauca communities’ encroachment into mangrove and saltmarsh communities was 388 ha in the 1997 period in comparison to 92 ha and 6.8 ha in the period 1997–2012 and 2012-2016 respectively.

Changes in extent of Casuarina glauca communities from 2012 to 2016

• During the period 2012-2016 there was 11 ha losses and 10 ha gain leading to a net loss of 1 ha, of Casuarina glauca communities in Moreton Bay. That is 44.6% loss of Casuarina glauca communities due to mangrove communities’ encroachment; encroachment of saltmarsh communities 28.5% and losses due to anthropogenic causes 27% mainly roads 45% and airport 26% in the Gold Coast 75%, Brisbane City 22% and Moreton Bay Regional 3% local government areas.
• 10 ha gain by encroachment: saltmarsh 67%, mangrove communities 1% and other 3%.

Additional information

• Coastal Wetlands of South East Queensland: Mapping and Survey 2001
• The Mangrove Vegetation of Moreton Bay 1986

References

1. ^ Accad, Arnon, Li, Jiaorong, Dowling, Ralph & Guymer, Gordon (2016), Mangrove and associated communities of Moreton Bay, Queensland, Australia: change in extent 1955-1997-2012. [online], Queensland Herbarium, Brisbane. Available at: https://www.publications.qld.gov.au/dataset/mangrove-and-associated-communities-of-moreton-bay.

Last updated: 17 June 2016