Extent and rate of change in estuarine wetlands
Key Finding
More than 96% of the pre-European settlement extent of estuarine wetlands in Queensland remained in 2017. Changes in the extent of estuarine wetlands in Queensland have been monitored since 2001. The highest rate of estuarine wetland loss was recorded during the 2001–2005 period (0.03%) mostly in the North East Coast drainage division.
Of the 2 broad estuarine wetland types — mangroves and salt marsh/salt flats — the greatest ongoing losses have occurred in salt marsh/salt flats in the North East Coast Drainage division.
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Queensland
At a statewide scale, about 96% of pre-clear extent of estuarine wetland remains. Estimated historical loss of estuarine wetlands is unevenly distributed across drainage divisions and basins:
- 81% remaining in the North East Coast non-Great Barrier Reef (Non-GBR) division
- 91% remaining in the North East Coast Great Barrier Reef (GBR) division
- close to 100% remaining in the Gulf division.
Ongoing loss over 2001–2017 continued, with the highest loss occurring during the 2001–2005 period totalling 345ha, at a rate of 86ha/yr. The 2013–2017 overall loss equated to 0.016% of 2017 extent.
- About 60ha of salt marsh/salt flat was lost in 2013–2017, statewide. North East Coast–GBR division accounted for 32ha.
- About 130ha of mangroves was lost in 2013–2017, statewide. North East Coast–non-GBR division accounted for 123ha, primarily associated with infrastructure development in South East Queensland.
The estimated historic and current loss of estuarine wetlands has mainly occurred due to draining and bunding associated with conversion of estuarine plains to freshwater wetlands.
In addition to the drainage divisions, the ‘other’ category represented in the data includes islands within Queensland waters, as well as discrepancies in basin coverages and coastline.
Disclaimer: The State of the Environment report 2020 (SoE2020) wetlands statistics are not comparable with previous SoE report figures. The SoE2020 statistics are based on the most recently available wetlands and other updated data. The different versions of the wetlands mapping (e.g. 2017 – v4; 2020 – v5) and other datasets are not comparable due to a number of factors such as updated source data, improved data capture methods. Therefore differences between SoE reports do not reflect an actual wetland extent change on-ground and only statistics within each SoE report should be compared.
Gulf
Historical loss of estuarine wetland extent in the Gulf drainage division has been minimal, with close to 100% remaining.
Loss over the 2001–2005, 2005–2009 and 2009–2013 periods was not detectable. During the 2013–2017 period, a loss of 0.16ha occurred in the Mission River sub-basin.
Disclaimer: The State of the Environment report 2020 (SoE2020) wetlands statistics are not comparable with previous SoE report figures. The SoE2020 statistics are based on the most recently available wetlands and other updated data. The different versions of the wetlands mapping (e.g. 2017 – v4; 2020 – v5) and other datasets are not comparable due to a number of factors such as updated source data, improved data capture methods. Therefore differences between SoE reports do not reflect an actual wetland extent change on-ground and only statistics within each SoE report should be compared.
North East Coast (GBR)
While 91% of pre-clear estuarine wetland remains within North East Coast Great Barrier Reef (GBR) drainage division, historical loss is unevenly distributed across basins. Many sub-basins, particularly in the Cape York peninsula area, have close to 100% remaining whereas the Lower Burdekin, Boyne, Shoalwater and Barron sub-basins have less than 75%.
Historical loss of estuarine wetland has been mostly salt flat/salt marsh (83% remaining) with less than 50% remaining in the Barron, Lower Burnett and Kolan catchments.
Sub-basins recording loss of estuarine wetlands of more than 10ha over the 2013–2017 period were:
- Bohle (14ha)
- Styx (13ha).
Loss during 2013–017 was 41ha — a rate of 10ha/yr, leaving 90% of the pre-clear extent in 2017. Of this, 32ha was salt marsh/salt flat wetlands.
Loss of mangrove wetland over 2013–2017 period was about 10ha. The majority of sub-basins had no detectable change.
Disclaimer: The State of the Environment report 2020 (SoE2020) wetlands statistics are not comparable with previous SoE report figures. The SoE2020 statistics are based on the most recently available wetlands and other updated data. The different versions of the wetlands mapping (e.g. 2017 – v4; 2020 – v5) and other datasets are not comparable due to a number of factors such as updated source data, improved data capture methods. Therefore differences between SoE reports do not reflect an actual wetland extent change on-ground and only statistics within each SoE report should be compared.
North East Coast (Non GBR)
There are 81% of pre-clear estuarine wetland remaining for the North East Coast non-Great Barrier Reef (non-GBR) drainage division.
- Coomera and Nerang sub-basin had less than 75% remaining.
- Brisbane and South Pine Rivers sub-basins had less than 50% remaining.
Overall loss of estuarine wetlands for the division was 150ha during the 2013–2017 period, at a rate of 38ha/yr. This equates with 0.6% of 2017 extent. Losses were primarily due to urban and infrastructure development.
Sub-basins recording loss of estuarine wetlands of more than 10ha over the 2013–2017 period were:
- Brisbane (26ha)
- South Pine (106ha).
Salt marsh/salt flat area was variable over the course of the 2001–2017 period. Initially, there were losses of 28ha, 17ha and 17ha in the 2001–2005, 2005–2009 and 2009–2013 periods respectively. There was a loss of 27ha during the 2013–2017 period.
Loss of mangrove wetlands has steadily increased from 16ha in 2001–2005 and 123ha in 2013–2017.
Disclaimer: The State of the Environment report 2020 (SoE2020) wetlands statistics are not comparable with previous SoE report figures. The SoE2020 statistics are based on the most recently available wetlands and other updated data. The different versions of the wetlands mapping (e.g. 2017 – v4; 2020 – v5) and other datasets are not comparable due to a number of factors such as updated source data, improved data capture methods. Therefore differences between SoE reports do not reflect an actual wetland extent change on-ground and only statistics within each SoE report should be compared.
More information:
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Metadata
Comparison between pre-clear (pre-European settlement extent) and remnant (current extent) estuarine wetland mapping. Data is based on the latest Queensland Wetland Mapping (version 5).
Change (loss or gain) in wetland extent as a result of clearing. Categories by broad wetland system definition classes: lacustrine, riverine, palustrine. Data is based on the latest Queensland Wetland Mapping (version 5).