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Wetlands and the carbon cycle

Wetlands are one of the most carbon-dense ecosystems on Earth[4]. They have high productivity and exchange large quantities of carbon with the atmosphere and terrestrial, freshwater, and marine ecosystems through regular flooding[8].

The role of wetlands in capturing and storing carbon is often underestimated. Globally, wetlands are estimated to store over a third of the world’s terrestrial carbon with blue carbon being one of the most important stores in Australia. Their destruction often results in major releases of greenhouse gases to the atmosphere. However, their role in the carbon cycle isn’t simple or easy to generalise.

Quick facts

Drainage
of peat bogs is estimated to produce emissions equal to 10% of all fossil fuel emissions (Ramsar).
Coastal ecosystems
within the Great Barrier Reef catchments hold a blue carbon stock of over 11 million tonnes (equivalent to the annual emissions of ~87 million cars)[1].

Figure 1: Queensland Wetlands Program 2012

 

Wetlands play a dynamic and crucial role in absorbing atmospheric carbon[7][2][6]. According to the Ramsar Scientific and Technical Review Panel, wetlands cover just 9% of the planet’s land surface, yet are estimated to store 35% of terrestrial carbon.

Generally, undisturbed, or intact wetlands tend to act as ‘carbon sinks’ due to their dense vegetation, algal activity and soils. They regulate processes such as anaerobic decomposition which generates methane and nitrous oxide. These gases respectively have 21 and 310 times more global warming impact than carbon dioxide over a 100 year timeframe[5][9]. However, the capacity of intact wetlands to absorb and sequester carbon varies widely depending on the type of wetland, temperature and water availability[6][2][3]. Research continues to better understand and identify the processes involved, and how these processes will be affected by climate change.

Fishermans Bay Photo by Cathy Ellis

As wetlands generally act as carbon sinks, their drainage and destruction can result in substantial carbon emissions[9]. Taking water out of a wetland means oxygen can reach previously inundated organic matter. This results in large emissions of carbon dioxide as the organic matter oxidises. Thus, the degradation of Queensland’s wetlands, especially melaleuca wetlands and mangroves, contributes to overall greenhouse gas emissions[3].

Of particular concern is the drainage and disturbance of potential acid sulphate soils, many of which underlay wetlands. When exposed to air these soils release large amounts of greenhouse gas emissions[5].

Australia’s wetlands are atypical due to the country’s dryness and climate variability. Coastal wetlands, especially tidal marshes, mangroves and seagrass are considered to have the greatest potential as carbon sinks in Australia. It has been estimated that every hectare of mangrove wetland stores about 550t of carbon.

Restoring and protecting wetlands presents an important opportunity for mitigating greenhouse gas emissions[9]. Globally, there is significant work underway to develop methodologies for restoring and managing wetlands that will support the generation of carbon credits. Australia has a Blue Carbon accounting model (BlueCAM)under the Commonwealth Government’s Carbon Farming Initiative.

Research supported by Queensland Government as part of the Land Restoration Fund and conducted by Deakin University’s Blue Carbon Lab has modelled blue carbon soil stocks for seagrass and mangroves in Great Barrier Reef Catchments.


References

  1. ^ Blue Carbon in the Great Barrier Reef catchment. [online] Available at: https://deakin.maps.arcgis.com/apps/Cascade/index.html?appid=b0cc86bd5dfb4dac8cc2d1ce2d8303b7 [Accessed 1 September 2020].
  2. ^ a b Coletti, JZ, Hinz, C, Vogwill, R & Hipsey, MR (2013), Hydrological controls on carbon metabolism in wetlands’, Ecological Modelling, vol. 249, pp. 3-3-18.
  3. ^ a b Commonwealth of Australia (2012), Issues Paper: The Role of Wetlands in the Carbon Cycle. [online] Available at: http://www.environment.gov.au/resource/issues-paper-role-wetlands-carbon-cycle.
  4. ^ Duarte, CM, Middelburg, JJ & Caraco, N (1 February 2005), 'Major role of marine vegetation on the oceanic carbon cycle', Biogeosciences. [online], vol. 2, no. 1, pp. 1-8. Available at: https://bg.copernicus.org/articles/2/1/2005/ [Accessed 14 September 2023].
  5. ^ a b Hicks, WS, Bowman, GM & Fitzpatrick, RW (1999), Environmental Impact of Acid Sulphate Soils near Cairns, Qld, vol. 15 (99), CSIRO Land and Water Technical Report.
  6. ^ a b Junk, WJ, An, S, Finlayson, CM, Gopa, B, Kvet, J, Mitchell, SA, Mitsch, W & Roberts, RD (2013), 'Current state of knowledge regarding the world’s wetlands and their future under global climate change: a synthesis', Aquatic Science. [online], vol. 75, pp. 151-151-167. Available at: https://link.springer.com/article/10.1007/s00027-012-0278-z.
  7. ^ Liu, Y, Ni, H, Zeng, Z & Chai, C (2013), Effect of disturbance on carbon cycling in wetland ecosystem’, Advanced Materials Research, pp. 3186-3186-3191.
  8. ^ Mitsch, WJ & Gosselink, J (2015), Wetlands, p. 213, Wiley, New Jersey, USA.
  9. ^ a b c Page, KL & Dalal, RC (2011), '1.   Contribution of natural and drained wetland systems to carbon stocks, CO2, N2O, CH4 fluxes: An Australian perspective', Soil Research. [online], vol. 49, no. 5, pp. 377-377-388. Available at: http://www.publish.csiro.au/?act=view_file&file_id=SR11024.pdf.
  10. ^ (16 June 2011). The Carbon Cycle. [online] Available at: https://earthobservatory.nasa.gov/features/CarbonCycle [Accessed 11 October 2023].

Last updated: 10 September 2020

This page should be cited as:

Department of Environment, Science and Innovation, Queensland (2020) Wetlands and the carbon cycle, WetlandInfo website, accessed 1 February 2024. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/ecology/processes-systems/carbon-cycle/wetlands-carbon-cycle/

Queensland Government
WetlandInfo   —   Department of Environment, Science and Innovation