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      Petroleum exploration increases methane emissions from northern peatlands

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          Abstract

          Peatlands are globally significant sources of atmospheric methane (CH 4). In the northern hemisphere, extensive geologic exploration activities have occurred to map petroleum deposits. In peatlands, these activities result in soil compaction and wetter conditions, changes that are likely to enhance CH 4 emissions. To date, this effect has not been quantified. Here we map petroleum exploration disturbances on peatlands in Alberta, Canada, where peatlands and oil deposits are widespread. We then estimate induced CH 4 emissions. By our calculations, at least 1900 km 2 of peatland have been affected, increasing CH 4 emissions by 4.4–5.1 kt CH 4 yr −1 above undisturbed conditions. Not currently estimated in Canada’s national reporting of greenhouse gas (GHG) emissions, inclusion would increase current emissions from land use, land use change and forestry by 7–8%. However, uncertainty remains large. Research further investigating effects of petroleum exploration on peatland GHG fluxes will allow appropriate consideration of these emissions in future peatland management.

          Abstract

          Human disturbance of peatland environments due to geological exploration activities can significantly alter peatland greenhouse gas exchange. Here, the authors study peatland disturbance in Alberta, Canada, and estimate that induced methane emissions are approximately 4.4–5.1 kt higher per year than in undisturbed conditions.

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          Most cited references36

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          Northern peatland carbon stocks and dynamics: a review

          Z. C. Yu (2012)
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            A synthesis of methane emissions from 71 northern, temperate, and subtropical wetlands.

            Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30-day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30-day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e.g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release.
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              Environmental and physical controls on northern terrestrial methane emissions across permafrost zones.

              Methane (CH4 ) emissions from the northern high-latitude region represent potentially significant biogeochemical feedbacks to the climate system. We compiled a database of growing-season CH4 emissions from terrestrial ecosystems located across permafrost zones, including 303 sites described in 65 studies. Data on environmental and physical variables, including permafrost conditions, were used to assess controls on CH4 emissions. Water table position, soil temperature, and vegetation composition strongly influenced emissions and had interacting effects. Sites with a dense sedge cover had higher emissions than other sites at comparable water table positions, and this was an effect that was more pronounced at low soil temperatures. Sensitivity analysis suggested that CH4 emissions from ecosystems where the water table on average is at or above the soil surface (wet tundra, fen underlain by permafrost, and littoral ecosystems) are more sensitive to variability in soil temperature than drier ecosystems (palsa dry tundra, bog, and fen), whereas the latter ecosystems conversely are relatively more sensitive to changes of the water table position. Sites with near-surface permafrost had lower CH4 fluxes than sites without permafrost at comparable water table positions, a difference that was explained by lower soil temperatures. Neither the active layer depth nor the organic soil layer depth was related to CH4 emissions. Permafrost thaw in lowland regions is often associated with increased soil moisture, higher soil temperatures, and increased sedge cover. In our database, lowland thermokarst sites generally had higher emissions than adjacent sites with intact permafrost, but emissions from thermokarst sites were not statistically higher than emissions from permafrost-free sites with comparable environmental conditions. Overall, these results suggest that future changes to terrestrial high-latitude CH4 emissions will be more proximately related to changes in moisture, soil temperature, and vegetation composition than to increased availability of organic matter following permafrost thaw.
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                Author and article information

                Contributors
                mstrack@uwaterloo.ca
                Journal
                Nat Commun
                Nat Commun
                Nature Communications
                Nature Publishing Group UK (London )
                2041-1723
                26 June 2019
                26 June 2019
                2019
                : 10
                : 2804
                Affiliations
                [1 ]ISNI 0000 0000 8644 1405, GRID grid.46078.3d, Department of Geography and Environmental Management, , University of Waterloo, ; Waterloo, ON N2L 3G1 Canada
                [2 ]ISNI 0000 0001 2184 7612, GRID grid.410334.1, Science and Technology Branch, , Environment and Climate Change Canada, ; Gatineau, QC K1A 0H3 Canada
                [3 ]ISNI 0000 0004 1936 7697, GRID grid.22072.35, Department of Geography, , University of Calgary, ; Calgary, AB T2N 1N4 Canada
                [4 ]ISNI 0000 0001 0284 1338, GRID grid.422810.d, Boreal Research Institute, , Northern Alberta Institute of Technology, ; Peace River, AB T8S 1R2 Canada
                Author information
                http://orcid.org/0000-0002-9943-265X
                http://orcid.org/0000-0001-8079-3730
                http://orcid.org/0000-0001-5386-6084
                Article
                10762
                10.1038/s41467-019-10762-4
                6594948
                67858c70-6d7f-4687-922f-89a0ebf69584
                © The Author(s) 2019

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 16 July 2018
                : 24 May 2019
                Funding
                Funded by: FundRef https://doi.org/10.13039/100010624, Climate Change and Emissions Management Corporation (CCCEMC);
                Award ID: B140020
                Award Recipient :
                Categories
                Article
                Custom metadata
                © The Author(s) 2019

                Uncategorized
                carbon cycle,environmental impact
                Uncategorized
                carbon cycle, environmental impact

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