Soil greenhouse gas fluxes from tropical coastal wetlands and alternative agricultural land uses
TL;DR: In this paper, the authors measured soil GHG fluxes from three natural coastal wetlands and two alternative agricultural land uses (sugarcane farming and pasture for cattle grazing) in tropical Australia.
Abstract: . Coastal wetlands are essential for regulating the global carbon
budget through soil carbon sequestration and greenhouse gas (GHG – CO2 , CH4 , and N2O ) fluxes. The conversion of coastal wetlands to
agricultural land alters these fluxes' magnitude and direction
(uptake/release). However, the extent and drivers of change of GHG fluxes are
still unknown for many tropical regions. We measured soil GHG fluxes from
three natural coastal wetlands – mangroves, salt marsh, and freshwater tidal
forests – and two alternative agricultural land uses – sugarcane farming and
pastures for cattle grazing (ponded and dry conditions). We assessed
variations throughout different climatic conditions (dry–cool, dry–hot, and
wet–hot) within 2 years of measurements (2018–2020) in tropical Australia.
The wet pasture had by far the highest CH4 emissions with 1231±386 mg m - 2 d - 1 , which were 200-fold higher than any other site.
Dry pastures and sugarcane were the highest emitters of N2O
with 55±9 mg m - 2 d - 1 (wet–hot period) and 11±3 m g m - 2 d - 1 (hot-dry period, coinciding with fertilisation), respectively. Dry
pastures were also the highest emitters of CO2 with 20±1 g m - 2 d - 1 (wet–hot period). The three coastal wetlands measured had
lower emissions, with salt marsh uptake of - 0.55 ± 0.23 and
- 1.19 ± 0.08 g m - 2 d - 1 of N2O and CO2 , respectively, during the dry–hot
period. During the sampled period, sugarcane and pastures had higher total
cumulative soil GHG emissions ( CH4+N2O ) of 7142 and 56 124 CO 2-eq kg ha - 1 yr - 1 compared to coastal wetlands with 144 to
884 CO 2-eq kg ha - 1 yr - 1 (where CO2-eq is CO2 equivalent). Restoring unproductive sugarcane
land or pastures (especially ponded ones) to coastal wetlands could provide
significant GHG mitigation.
Citations
More filters
TL;DR: In this article , the feasibility of achieving quantified and secure carbon removal (negative emissions) through the restoration of coastal vegetation has been evaluated, with the conclusion that costs are highly uncertain, with lower-range estimates unrealistic for wider application, and that carbon removal using coastal blue carbon restoration therefore has questionable cost-effectiveness when considered only as a climate mitigation action, either for carbon offsetting or for inclusion in Nationally Determined Contributions.
Abstract: Mangrove forests, seagrass meadows and tidal saltmarshes are vegetated coastal ecosystems that accumulate and store large quantities of carbon in their sediments. Many recent studies and reviews have favorably identified the potential for such coastal “blue carbon” ecosystems to provide a natural climate solution in two ways: by conservation, reducing the greenhouse gas emissions arising from the loss and degradation of such habitats, and by restoration, to increase carbon dioxide drawdown and its long-term storage. The focus here is on the latter, assessing the feasibility of achieving quantified and secure carbon removal (negative emissions) through the restoration of coastal vegetation. Seven issues that affect the reliability of carbon accounting for this approach are considered: high variability in carbon burial rates; errors in determining carbon burial rates; lateral carbon transport; fluxes of methane and nitrous oxide; carbonate formation and dissolution; vulnerability to future climate change; and vulnerability to non-climatic factors. Information on restoration costs is also reviewed, with the conclusion that costs are highly uncertain, with lower-range estimates unrealistic for wider application. CO2 removal using coastal blue carbon restoration therefore has questionable cost-effectiveness when considered only as a climate mitigation action, either for carbon-offsetting or for inclusion in Nationally Determined Contributions. Many important issues relating to the measurement of carbon fluxes and storage have yet to be resolved, affecting certification and resulting in potential over-crediting. The restoration of coastal blue carbon ecosystems is nevertheless highly advantageous for climate adaptation, coastal protection, food provision and biodiversity conservation. Such action can therefore be societally justified in very many circumstances, based on the multiple benefits that such habitats provide at the local scale.
20 citations
TL;DR: In this paper , the authors describe the development of a blue carbon accounting model (BlueCAM) used within the Tidal Restoration of Blue Carbon Ecosystems Methodology Determination 2022 of the Emissions Reduction Fund (ERF), which is Australia's voluntary carbon market scheme.
Abstract: Restoration of coastal wetlands has the potential to deliver both climate change mitigation, called blue carbon, and adaptation benefits to coastal communities, as well as supporting biodiversity and providing additional ecosystem services. Valuing carbon sequestration may incentivize restoration projects; however, it requires development of rigorous methods for quantifying blue carbon sequestered during coastal wetland restoration. We describe the development of a blue carbon accounting model (BlueCAM) used within the Tidal Restoration of Blue Carbon Ecosystems Methodology Determination 2022 of the Emissions Reduction Fund (ERF), which is Australia's voluntary carbon market scheme. The new BlueCAM uses Australian data to estimate abatement from carbon and greenhouse gas sources and sinks arising from coastal wetland restoration (via tidal restoration) and aligns with the Intergovernmental Panel for Climate Change guidelines for national greenhouse gas inventories. BlueCAM includes carbon sequestered in soils and biomass and avoided emissions from alternative land uses. A conservative modeled approach was used to provide estimates of abatement (as opposed to on-ground measurements); and in doing so, this will reduce the costs associated with monitoring and verification for ERF projects and may increase participation in blue carbon projects by Australian landholders. BlueCAM encompasses multiple climate regions and plant communities and therefore may be useful to others outside Australia seeking to value blue carbon benefits from coastal wetland restoration.
13 citations
TL;DR: In this paper , the authors measured levels of carbon (C) abatement and nitrogen removal potential of restored coastal wetlands in subtropical Queensland, Australia, and calculated C abatements of 18.5 Mg CO2−eq ha−1
Abstract: Abstract Coastal wetland restoration is an important activity to achieve greenhouse gas (GHG) reduction targets, improve water quality, and reach the Sustainable Development Goals. However, many uncertainties remain in connection with achieving, measuring, and reporting success from coastal wetland restoration. We measured levels of carbon (C) abatement and nitrogen (N) removal potential of restored coastal wetlands in subtropical Queensland, Australia. The site was originally a supratidal forest composed of Melaleuca spp. that was cleared and drained in the 1990s for sugarcane production. In 2010, tidal inundation was reinstated, and a mosaic of coastal vegetation (saltmarshes, mangroves, and supratidal forests) emerged. We measured soil GHG fluxes (CH4, N2O, CO2) and sequestration of organic C in the trees and soil to estimate the net C abatement associated with the reference, converted, and restored sites. To assess the influence of restoration on water quality improvement, we measured denitrification and soil N accumulation. We calculated C abatement of 18.5 Mg CO2−eq ha−1 year−1 when sugarcane land transitioned to supratidal forests, 11.0 Mg CO2−eq ha−1 year−1 when the land transitioned to mangroves, and 6.2 Mg CO2−eq ha−1 year−1 when the land transitioned to saltmarshes. The C abatement was due to tree growth, soil accumulation, and reduced N2O emissions due to the cessation of fertilization. Carbon abatement was still positive, even accounting for CH4 emissions, which increased in the wetlands due to flooding and N2O production due to enhanced levels of denitrification. Coastal wetland restoration in this subtropical setting effectively reduces CO2 emissions while providing additional cobenefits, notably water quality improvement.
8 citations
TL;DR: In this article, a conceptual framework was developed to synthesise and visualise the fate and transport of nitrogen from the catchments to the sea from a literature review, which can be applied to other ecosystems to understand the transport and fate of N within and between catchments.
3 citations
TL;DR: In this paper , the authors analyzed a regional database of >26,000 N 2 O chamber flux measurements sampled across >150 wetlands from the Prairie Pothole Region (PPR) in the Great Plains of North America.
3 citations
References
More filters
Brown University1, Stanford University2, University of New Mexico3, University of Connecticut4, University of Southern California5, University of California, Merced6, University of Washington7, National Science Foundation8, Los Alamos National Laboratory9, Rutgers University10, Columbia University11, University of Bergen12, Portland State University13, University of Kansas14
TL;DR: Current evidence confirms that, as proposed by the Baas-Becking hypothesis, 'the environment selects' and is, in part, responsible for spatial variation in microbial diversity, but recent studies also dispute the idea that 'everything is everywhere'.
Abstract: We review the biogeography of microorganisms in light of the biogeography of macroorganisms A large body of research supports the idea that free-living microbial taxa exhibit biogeographic patterns Current evidence confirms that, as proposed by the Baas-Becking hypothesis, 'the environment selects' and is, in part, responsible for spatial variation in microbial diversity However, recent studies also dispute the idea that 'everything is everywhere' We also consider how the processes that generate and maintain biogeographic patterns in macroorganisms could operate in the microbial world
2,456 citations
TL;DR: The Global Lakes and Wetlands Database (GLWD) as mentioned in this paper was created by combining the best available sources for lakes and wetlands on a global scale and the application of Geographic Information System (GIS) functionality enabled the generation of a database which focuses in three coordinated levels on (1) large lakes and reservoirs, (2) smaller water bodies, and (3) wetlands.
1,938 citations
Centre national de la recherche scientifique1, Commonwealth Scientific and Industrial Research Organisation2, National Oceanic and Atmospheric Administration3, United States Department of Energy4, University of California, Irvine5, Seconda Università degli Studi di Napoli6, Central Maine Community College7, Max Planck Society8, Swiss Federal Institute for Forest, Snow and Landscape Research9, Utrecht University10, Carma11, National Center for Atmospheric Research12, University of East Anglia13, Massachusetts Institute of Technology14, VU University Amsterdam15, Goddard Space Flight Center16, University of Bern17, Nagoya University18, Imperial College London19, Royal Netherlands Meteorological Institute20, University of California, San Diego21, National Institute of Water and Atmospheric Research22
TL;DR: In this paper, the authors construct decadal budgets for methane sources and sinks between 1980 and 2010, using a combination of atmospheric measurements and results from chemical transport models, ecosystem models, climate chemistry models and inventories of anthropogenic emissions.
Abstract: Methane is an important greenhouse gas, responsible for about 20% of the warming induced by long-lived greenhouse gases since pre-industrial times. By reacting with hydroxyl radicals, methane reduces the oxidizing capacity of the atmosphere and generates ozone in the troposphere. Although most sources and sinks of methane have been identified, their relative contributions to atmospheric methane levels are highly uncertain. As such, the factors responsible for the observed stabilization of atmospheric methane levels in the early 2000s, and the renewed rise after 2006, remain unclear. Here, we construct decadal budgets for methane sources and sinks between 1980 and 2010, using a combination of atmospheric measurements and results from chemical transport models, ecosystem models, climate chemistry models and inventories of anthropogenic emissions. The resultant budgets suggest that data-driven approaches and ecosystem models overestimate total natural emissions. We build three contrasting emission scenarios-which differ in fossil fuel and microbial emissions-to explain the decadal variability in atmospheric methane levels detected, here and in previous studies, since 1985. Although uncertainties in emission trends do not allow definitive conclusions to be drawn, we show that the observed stabilization of methane levels between 1999 and 2006 can potentially be explained by decreasing-to-stable fossil fuel emissions, combined with stable-to-increasing microbial emissions. We show that a rise in natural wetland emissions and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006, although the relative contribution of these two sources remains uncertain. © 2013 Macmillan Publishers Limited.
1,668 citations
1,288 citations
TL;DR: In this article, the potential benefits of conservation, restoration and use of marine vegetated habitats for coastal protection and climate change mitigation are assessed, and the potential benefit of using these habitats in eco-engineering solutions for coast protection is discussed.
Abstract: Marine vegetated habitats occupy a small fraction of the ocean surface, but contribute about 50% of the carbon that is buried in marine sediments. In this Review the potential benefits of conservation, restoration and use of these habitats for coastal protection and climate change mitigation are assessed. Marine vegetated habitats (seagrasses, salt-marshes, macroalgae and mangroves) occupy 0.2% of the ocean surface, but contribute 50% of carbon burial in marine sediments. Their canopies dissipate wave energy and high burial rates raise the seafloor, buffering the impacts of rising sea level and wave action that are associated with climate change. The loss of a third of the global cover of these ecosystems involves a loss of CO2 sinks and the emission of 1 Pg CO2 annually. The conservation, restoration and use of vegetated coastal habitats in eco-engineering solutions for coastal protection provide a promising strategy, delivering significant capacity for climate change mitigation and adaption.
1,239 citations