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Open accessJournal ArticleDOI: 10.1088/1748-9326/ABEB36

Global importance of methane emissions from drainage ditches and canals

02 Mar 2021-Environmental Research Letters (IOP Publishing)-Vol. 16, Iss: 4, pp 044010
Abstract: Globally, there are millions of kilometres of drainage ditches which have the potential to emit the powerful greenhouse gas methane (CH4), but these emissions are not reported in budgets of inland waters or drained lands. Here, we synthesise data to show that ditches spanning a global latitudinal gradient and across different land uses emit large quantities of CH4 to the atmosphere. Area-specific emissions are comparable to those from lakes, streams, reservoirs, and wetlands. While it is generally assumed that drainage negates terrestrial CH4 emissions, we find that CH4 emissions from ditches can, on average, offset ~10% of this reduction. Using global areas of drained land we show that ditches contribute 3.5 Tg CH4 yr-1 (0.6–10.5 Tg CH4 yr-1); equivalent to 0.2–3% of global anthropogenic CH4 emissions. A positive relationship between CH4 emissions and temperature was found, and emissions were highest from eutrophic ditches. We advocate the inclusion of ditch emissions in national GHG inventories, as neglecting them can lead to incorrect conclusions concerning the impact of drainage-based land management on CH4 budgets.

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Topics: Ditch (53%), Drainage (52%), Greenhouse gas (52%)
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Open accessJournal ArticleDOI: 10.1007/S13157-021-01465-Y
19 Feb 2021-Wetlands
Abstract: Small water bodies including drainage ditches can be hotspots for methane (CH4) emissions from peatlands. We assessed the CH4 emissions of a drained and a rewetted temperate fen including emissions of managed and unmanaged drainage ditches over the course of 2.5 years, covering three vegetation periods. Ditch CH4 emissions in the rewetted fen were significantly higher than in the drained fen. In the rewetted fen ditches contributed up to 91% of the annual CH4 budget, despite covering only 1.5% of the area. In the drained fen CH4 emissions were solely made up of ditch emissions. When including CH4 uptake by the peat soil, the CH4 balance of the drained fen was neutral. Dissolved organic carbon concentrations likely had an enhancing effect on CH4 emissions while nitrate and sulfate in the ditch water seem to have had an inhibitory effect. Air and water temperature controlled seasonal variability of ebullitive as well as diffusive CH4 emissions. Ebullition contributed less than 10% to the overall CH4 budget in the ditches. Drainage ditches represent a hotspot of CH4 emissions and need therefore be taken into account when assessing the success of rewetting projects of peatlands.

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Topics: Ditch (58%), Peat (52%), Drainage (51%)

1 Citations


Open accessJournal ArticleDOI: 10.5194/BG-18-5085-2021
Naima Iram1, Emad Kavehei1, Damien T. Maher2, Stuart E. Bunn1  +3 moreInstitutions (2)
16 Sep 2021-Biogeosciences
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.

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Topics: Salt marsh (53%), Wetland (52%)

1 Citations


Open accessJournal ArticleDOI: 10.1111/GCB.15762
Mike Peacock1, Joachim Audet2, David Bastviken3, Sarah Cook4  +7 moreInstitutions (8)
Abstract: Inland waters play an active role in the global carbon cycle and emit large volumes of the greenhouse gases (GHGs) methane (CH ) and carbon dioxide (CO ). A considerable body of research has improved emissions estimates from lakes, reservoirs, and rivers but recent attention has been drawn to the importance of small, artificial waterbodies as poorly quantified but potentially important emission hotspots. Of particular interest are emissions from drainage ditches and constructed ponds. These waterbody types are prevalent in many landscapes and their cumulative surface areas can be substantial. Furthermore, GHG emissions from constructed waterbodies are anthropogenic in origin and form part of national emissions reporting, whereas emissions from natural water bodies do not (according to Intergovernmental Panel on Climate Change guidelines). Here, we present GHG data from two complementary studies covering a range of land uses. In the first, we measured emissions from nine ponds and seven ditches over a full year. Annual emissions varied considerably: 0.1 - 44.3 g CH m yr and -36 - 4421 g CO m yr . In the second, we measured GHG concentrations in 96 ponds and 64 ditches across seven countries, covering subtropical, temperate and sub-arctic biomes. When CH emissions were converted to CO equivalents, 93% of waterbodies were GHG sources. In both studies, GHGs were positively related to nutrient status (C, N, P), and pond GHG concentrations were highest in smallest waterbodies. Ditch and pond emissions were larger per unit area when compared to equivalent natural systems (streams, natural ponds). We show that GHG emissions from natural systems should not be used as proxies for those from artificial waterbodies, and that artificial waterbodies have the potential to make a substantial but largely unquantified contribution to emissions from the Agriculture, Forestry and Other Land Use sector, and the global carbon cycle.

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Topics: Greenhouse gas (54%), Carbon cycle (52%)

1 Citations



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53 results found


Journal ArticleDOI: 10.1007/S10021-006-9013-8
13 Feb 2007-Ecosystems
Abstract: Because freshwater covers such a small fraction of the Earth’s surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y−1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y−1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described.

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Topics: Freshwater ecosystem (60%), Carbon cycle (57%), Aquatic ecosystem (56%) ... show more

2,751 Citations


Journal ArticleDOI: 10.1038/NGEO618
01 Sep 2009-Nature Geoscience
Abstract: The terrestrial biosphere is assumed to take up most of the carbon on land. However, it is becoming clear that inland waters process large amounts of organic carbon and must be considered in strategies to mitigate climate change.

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Topics: Permafrost carbon cycle (72%), Carbon cycle (70%), Carbon (59%) ... show more

1,072 Citations


Open accessJournal ArticleDOI: 10.1126/SCIENCE.1196808
07 Jan 2011-Science
Abstract: Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH4) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets. Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least 103 teragrams of CH4 year−1, corresponding to 0.65 petagrams of C as carbon dioxide (CO2) equivalents year−1, offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.

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Topics: Carbon sink (58%), Greenhouse gas (58%), Carbon cycle (57%) ... show more

997 Citations


Journal ArticleDOI: 10.1023/A:1005929032764
27 Jul 1998-Biogeochemistry
Abstract: Potential rates of both methane production and methane consumption vary over three orders of magnitude and their distribution is skew. These rates are weakly correlated with ecosystem type, incubation temperature, in situ aeration, latitude, depth and distance to oxic/anoxic interface. Anaerobic carbon mineralisation is a major control of methane pro- duction. The large range in anaerobic CH4:CO2 production rates indicate that a large part of the anaerobically mineralised carbon is used for reduction of electron acceptors, and, hence, is not available for methanogenesis. Consequently, cycling of electron acceptors needs to be studied to understand methane production. Methane and oxygen half saturation constants for methane oxidation vary about one order of magnitude. Potential methane oxidation seems to be correlated with methanotrophic biomass. Therefore, variation in potential methane oxidation could be related to site characteristics with a model of methanotrophic biomass.

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Topics: Anaerobic oxidation of methane (73%), Methanogenesis (65%), Methane (62%)

775 Citations


Open accessJournal ArticleDOI: 10.1029/2004GB002238
Abstract: [ 1] Lake sediments are "hot spots'' of methane production in the landscape. However, regional and global lake methane emissions, contributing to the greenhouse effect, are poorly known. We develop ...

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Topics: Greenhouse gas (55%), Greenhouse effect (52%), Methane (51%) ... show more

773 Citations


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