Concerns and uncertainties relating to methane emissions synthesis for vegetated coastal ecosystems

Rosentreter, Judith A.; Williamson, Phillip

doi:10.1111/gcb.15201

Cited by 13 publications

(5 citation statements)

References 9 publications

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“…The mean CH 4 concentration for mineral soil catchments is beyond the interquartile range (Figure 6) and this (along with the same finding for the CH 4 fluxes in Figure 2) revels the skewed nature of the CH 4 concentration and flux data. The skewed nature of CH 4 data is well known and brings forth the issue of whether to use the median or mean for upscaling and comparisons (Rosentreter & Williamson, 2020). However, assuming that sampling efforts have not been biased toward measuring GHG hotspots, these high emitting sites are representative of the entire population and thus the mean is the better measure (Al‐Haj & Fulweiler, 2020; Paneer Selvam et al., 2014).…”

Section: Discussionmentioning

confidence: 99%

Significant Emissions From Forest Drainage Ditches—An Unaccounted Term in Anthropogenic Greenhouse Gas Inventories?

et al. 2021

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Introduction"In the beginning there was a mire, a ditching mattock and Jussi"The opening lines of the Finnish novel Under the North Star (published 1959) by Väinö Linna, in which the farm hand Jussi is draining a mire.Drainage ditches are common features of many production landscapes. They are constructed for various reasons but are generally used to lower the terrestrial water table in order to improve agricultural and forest productivity, by increasing both vegetation rooting depth and nutrient availability via the decomposition of organic matter. There is a wide variety of ditch morphologies and characteristics; it is not unusual for Abstract Forestry is a natural climate solution for removing atmospheric carbon dioxide (CO 2 ) and reaching net zero emissions. Managed boreal forests typically have extensive drainage ditch networks, and these can be hotspots of anthropogenic greenhouse gas (GHG) emissions, potentially offsetting the terrestrial carbon gain. However, there is a lack of data detailing GHG emissions from ditches on mineral soils, where most boreal forestry occurs. Here, we address this knowledge gap using two approaches. First, we conducted a synoptic campaign to measure summer GHG fluxes from 109 boreal forest ditches draining mineral soils within one local region. We found a clear control of ditch water level on methane (CH 4 ), with zero emissions from dry ditches and variable, but often high, emissions from water-filled ditches. Almost all ditches acted as sources of CO 2 , regardless of water status. Second, we reanalyzed a published data set of boreal forest ditches and streams across three regions where GHG concentrations had been repeatedly measured and detailed catchment information was available. Within this data set we categorized 76 ditches into mineral and peatland catchments and detected no difference in mean CH 4 and CO 2 concentrations between the two soil types. GHG emissions from ditches draining mineral forest soils can be as large as those from peatland forest ditches. Using literature values for forest GHG uptake we demonstrate that ditch CH 4 emissions are particularly important and can offset the terrestrial CH 4 uptake. Ignoring ditch emissions, which are anthropogenic in origin, will lead to incorrect estimates of the landscape-scale forest GHG budget.Plain Language Summary Managed boreal forests can remove large amounts of carbon dioxide from the atmosphere. It is hoped that this removal will go some way to counteracting anthropogenic greenhouse gas (GHG) emissions. However, forests often contain networks of humanconstructed drainage ditches which can be hotspots for emissions of methane, a powerful GHG. Most boreal forests are found on mineral soils but there is almost no information concerning the size of forest ditch GHG emissions from these soils. We measured GHGs in a large number of boreal forest ditches and found that emissions were of a similar average size from ditches draining mineral and peat soils. Dry ditches emitted no methane, but water-filled ditches emitt...

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Section: Discussionmentioning

confidence: 99%

Significant Emissions From Forest Drainage Ditches—An Unaccounted Term in Anthropogenic Greenhouse Gas Inventories?

et al. 2021

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“…This total has the potential to fully counteract the climatic benefits of carbon burial by these ecosystems. However, statistical methods affect these estimates and comparisons, with lower global values for CH 4 emissions obtained when based on the median, rather than the arithmetic mean, of site-specific studies (Rosentreter and Williamson, 2020). As discussed in Box 1, the arithmetic mean is best avoided for highly skewed distributions.…”

Section: Fluxes Of Methane and Nitrous Oxidementioning

confidence: 99%

Carbon Removal Using Coastal Blue Carbon Ecosystems Is Uncertain and Unreliable, With Questionable Climatic Cost-Effectiveness

Williamson

Gattuso

2022

Front. Clim.

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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.

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“…In an estimation of global ES, Costanza et al (2014) point out that the loss of ES between 1997 and 2011 due to land change lies between $4.3 and $20.2 trillion/year in 2007 $US. The core of restoration programs lies in our ability to quantify the value of Blue Carbon sequestration-also considering large uncertainty about methane emissions (Rosentreter and Williamson, 2020)-which would lead to the acquisition of carbon credits by countries investing in the calculated restoration of specific coastal ecosystems with high carbon potential (Kroeger et al, 2017;Tang et al, 2018).…”

Section: What Does the Valuation Of Natural Capital Serve?mentioning

confidence: 99%

The Role of Blue Carbon in Climate Change Mitigation and Carbon Stock Conservation

et al. 2021

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The potential for Blue Carbon ecosystems to combat climate change and provide co-benefits was discussed in the recent and influential Intergovernmental Panel on Climate Change Special Report on the Ocean and Cryosphere in a Changing Climate. In terms of Blue Carbon, the report mainly focused on coastal wetlands and did not address the socio-economic considerations of using natural ocean systems to reduce the risks of climate disruption. In this paper, we discuss Blue Carbon resources in coastal, open-ocean and deep-sea ecosystems and highlight the benefits of measures such as restoration and creation as well as conservation and protection in helping to unleash their potential for mitigating climate change risks. We also highlight the challenges—such as valuation and governance—to marshaling their mitigation role and discuss the need for policy action for natural capital market development, and for global coordination. Efforts to identify and resolve these challenges could both maintain and harness the potential for these natural ocean systems to store carbon and help fight climate change. Conserving, protecting, and restoring Blue Carbon ecosystems should become an integral part of mitigation and carbon stock conservation plans at the local, national and global levels.

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Concerns and uncertainties relating to methane emissions synthesis for vegetated coastal ecosystems

Abstract: This is a Letter to the Editor on Al‐Haj and Fulweiler, 26, https://doi.org/10.1111/gcb.15046. See also the Response to this Letter by Al‐Haj and Fulweiler, 26, https://doi.org/10.1111/gcb.15245

Cited by 13 publications

References 9 publications

Significant Emissions From Forest Drainage Ditches—An Unaccounted Term in Anthropogenic Greenhouse Gas Inventories?

Significant Emissions From Forest Drainage Ditches—An Unaccounted Term in Anthropogenic Greenhouse Gas Inventories?

Carbon Removal Using Coastal Blue Carbon Ecosystems Is Uncertain and Unreliable, With Questionable Climatic Cost-Effectiveness

The Role of Blue Carbon in Climate Change Mitigation and Carbon Stock Conservation

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