David R. Piatka
Johannes A. C. Barth
Ralf Kiese- 1Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
- 2Department of Geography and Geosciences, GeoZentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
Editorial on the Research Topic
Greenhouse gas emissions from terrestrial freshwater ecosystems: spatial and temporal hot spots
Terrestrial freshwater ecosystems are increasingly recognized as crucial components of the global carbon (C) and nitrogen (N) cycles. These cycles include matter transfer from terrestrial to aquatic compartments, sediment storage, biogeochemical turnover, and losses via downstream transport of dissolved and particulate species and gaseous emissions to the atmosphere (Beusen et al., 2005; Marx et al., 2017; Drake et al., 2018; Piatka et al., 2022; Zheng et al., 2022; Wang et al., 2023). Losses of gases are climate-critical when they concern greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) (Intergovernmental Panel on Climate Change, 2021, 2022). A recent synthesis study estimates yearly emissions of 8.3 (5.7–12.7) Pg CO2-equivalents (CO2-eq) from inland water bodies scaled over 100 years (Lauerwald et al., 2023). This number may still be severely underestimated due to excluding a poorly defined number of small lentic freshwater ecosystems and wetlands (Downing et al., 2012; Lauerwald et al., 2023). The collection of manuscripts in this Research Topic “Greenhouse gas emissions from terrestrial freshwater ecosystems: spatial and temporal hot spots” provides a schematic overview of GHG sources and turnover.
In recent centuries and decades, human activities have caused substantial changes in landscape hydrology, land use, and climate. These activities also affected the functioning of terrestrial freshwater ecosystems and GHG exchange (Piatka et al., 2021; Winkler et al., 2021; Pilla et al., 2022; Mwanake et al., 2023). Due to their sensitivity to these changing environmental conditions and their complex temporal and spatial nature, large-scale quantifications of current global freshwater GHG emissions are still subject to large uncertainties. The complexity of these processes, together with their quantitative uncertainties and feedback loops, call for improved biogeochemical, physical, and biological understanding and quantification of processes.
The manuscript by Mwanake et al. investigates a critical knowledge gap in our understanding of partitioning GHG sources in headwater streams on the catchment scale. Employing stable isotope ratios of oxygen (O) and hydrogen (H), they analyse the influence of mean residence times (MRTs) and young water fractions (YWFs) on GHG concentrations in 17 headwater streams with variable catchment characteristics that cover variable land use types and proportions and catchment drainage. Their work reveals that agriculture-dominated stream catchments can act as seasonal hotspots of GHGs. The work also shows that variable shorter and longer MRTs from inputs of precipitation-driven GHG-rich agricultural soils and nutrient-rich groundwaters can fuel in-stream GHG production.
Similarly strong impacts of temporally dynamic hydrological conditions and land use on GHG concentrations and respective emissions in a peatland-dominated headwater stream are also shown in the study of Piatka et al.. By applying a continuous measuring system for the three GHGs CO2, CH4, and N2O over 5 months, this study shows increased mobilization of GHG-rich peatland porewaters to the stream network after rainfall events. Subsequent higher stream water levels enhanced GHG emissions that may be responsible for up to 59% of the total GHG budget.
Addressing the burgeoning aquaculture sector, the study by Vroom et al. investigates CH4 emissions from freshwater fishponds in Brazil. The study reveals the dominance of CH4 ebullition over diffusion. This finding emphasizes the significance of GHG emissions from managed and artificial ponds. These results challenge our understanding of CH4 emission pathways in aquaculture ponds and call for management practices to minimize their carbon footprint.
Although mostly neglected, aquatic vegetation might also strongly contribute to the dynamics and magnitudes of CH4 emissions from terrestrial freshwater ecosystems. This relationship is highlighted in the review by Bodmer et al.. In a literature synthesis, they present various pathways in which aquatic vegetation may influence CH4 dynamics and emissions. They also assemble a variety of measurement methods to assess plant-associated CH4 fluxes. Based on a complementary data analysis from the literature, the authors demonstrate that neglecting vegetated habitats may lead to a substantial underestimation of global CH4 emissions from inland waters.
Specifically, water bodies with a higher impact of anthropogenic pressure caused by land use change are often major sources of GHGs, as various recent studies suggest (Hao et al., 2021; Li et al., 2021; Peacock et al., 2021; Rosentreter et al., 2021; Malerba et al., 2022).
Moreover, a new study by Zannella et al. investigates how harvesting forests affects the dynamics of CO2 in man-made ditches in boreal watercourses. The researchers propose that light- and temperature-induced metabolism is important. They also point out the seasonal variations and diel cycles in CO2 concentrations. This study emphasizes the significance of taking these dynamics into account when analyzing CO2 emissions in boreal areas impacted by forestry.
The five manuscripts in this Research Topic add new data, concepts, knowledge and improved process understanding of GHG dynamics from catchment to freshwater habitat scales. All of these studies show that continental freshwaters are essential but increasingly scarce resources. They also show that societies and regulations need to value and reduce anthropogenic impacts on inland water bodies to minimize aquatic GHG emissions and maintain freshwater ecosystem services.
Author contributions
DP: Writing – original draft, Writing – review & editing. JB: Writing – review & editing. RK: Writing – review & editing.
Funding
The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.
Publisher's note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
References
Beusen, A. H. W., Dekkers, A. L. M., Bouwman, A. F., Ludwig, W., and Harrison, J. (2005). Estimation of global river transport of sediments and associated particulate C, N, and P. Global Biogeochem. Cycles 19, 4. doi: 10.1029/2005GB002453
Downing, J. A., Cole, J. J., Duarte, C. M., Middelburg, J. J., Melack, J. M., Prairie, Y. T., et al. (2012). Global abundance and size distribution of streams and rivers. Inland Waters 2, 229–236. doi: 10.5268/IW-2.4.502
Drake, T. W., Raymond, P. A., and Spencer, R. G. M. (2018). Terrestrial carbon inputs to inland waters: a current synthesis of estimates and uncertainty. Limnol. Oceanography Lett. 3, 132–142. doi: 10.1002/lol2.10055
Hao, X., Ruihong, Y., Zhuangzhuang, Z., Zhen, Q., Xixi, L., Tingxi, L., et al. (2021). Greenhouse gas emissions from the water–air interface of a grassland river: a case study of the Xilin River. Sci. Rep. 11, 2659. doi: 10.1038/s41598-021-81658-x
Intergovernmental Panel on Climate Change (2021). Climate Change 2021 – The Physical Science Basis: Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press.
Intergovernmental Panel on Climate Change (2022). Global Warming of 1.5°C: IPCC Special Report on Impacts of Global Warming of 1.5°C above Pre-industrial Levels in Context of Strengthening Response to Climate Change, Sustainable Development, and Efforts to Eradicate Poverty. Cambridge: Cambridge University Press.
Lauerwald, R., Allen, G. H., Deemer, B. R., Liu, S., Maavara, T., Raymond, P., et al. (2023). Inland water greenhouse gas budgets for RECCAP2:2. Regionalization and homogenization of estimates. Global Biogeochem. Cycl. 37, e2022GB007658. doi: 10.1029/2022GB007658
Li, M., Peng, C., Zhang, K., Xu, L., Wang, J., Yang, Y., et al. (2021). Headwater stream ecosystem: an important source of greenhouse gases to the atmosphere. Water Res. 190, 116738. doi: 10.1016/j.watres.2020.116738
Malerba, M. E., de Kluyver, T., Wright, N., Schuster, L., and Macreadie, P. I. (2022). Methane emissions from agricultural ponds are underestimated in national greenhouse gas inventories. Communi. Earth Environm. 3, 306. doi: 10.1038/s43247-022-00638-9
Marx, A., Dusek, J., Jankovec, J., Sanda, M., Vogel, T., van Geldern, R., et al. (2017). A review of CO2 and associated carbon dynamics in headwater streams: a global perspective. Rev. Geophys. 55, 560–585. doi: 10.1002/2016RG000547
Mwanake, R. M., Gettel, G. M., Wangari, E. G., Glaser, C., Houska, T., Breuer, L., et al. (2023). Anthropogenic activities significantly increase annual greenhouse gas (GHG) fluxes from temperate headwater streams in Germany. Biogeosciences 20, 3395–3422. doi: 10.5194/bg-20-3395-2023
Peacock, M., Audet, J., Bastviken, D., Cook, S., Evans, C. D., Grinham, A., et al. (2021). Small artificial waterbodies are widespread and persistent emitters of methane and carbon dioxide. Glob. Chang. Biol. 27, 5109–5123. doi: 10.1111/gcb.15762
Piatka, D. R., Frank, A. H., Köhler, I., Castiglione, K., van Geldern, R., and Barth, J. A. C. (2022). Balance of carbon species combined with stable isotope ratios show critical switch towards bicarbonate uptake during cyanobacteria blooms. Sci. Total Environm. 807, 151067. doi: 10.1016/j.scitotenv.2021.151067
Piatka, D. R., Wild, R., Hartmann, J., Kaule, R., Kaule, L., Gilfedder, B., et al. (2021). Transfer and transformations of oxygen in rivers as catchment reflectors of continental landscapes: a review. Earth-Sci. Rev. 220, 103729. doi: 10.1016/j.earscirev.2021.103729
Pilla, R. M., Griffiths, N. A., Gu, L., Kao, S.-C., McManamay, R., Ricciuto, D. M., et al. (2022). Anthropogenically driven climate and landscape change effects on inland water carbon dynamics: what have we learned and where are we going? Glob. Chang. Biol. 28, 5601–5629. doi: 10.1111/gcb.16324
Rosentreter, J. A., Borges, A. V., Deemer, B. R., Holgerson, M. A., Liu, S., Song, C., et al. (2021). Half of global methane emissions come from highly variable aquatic ecosystem sources. Nat. Geosci. 14, 225–230. doi: 10.1038/s41561-021-00715-2
Wang, J., Vilmin, L., Mogollón, J. M., Beusen, A. H. W., van Hoek, W. J., Liu, X., et al. (2023). Inland waters increasingly produce and emit nitrous oxide. Environ. Sci. Technol. 57, 13506–13519. doi: 10.1021/acs.est.3c04230
Winkler, K., Fuchs, R., Rounsevell, M., and Herold, M. (2021). Global land use changes are four times greater than previously estimated. Nat. Commun. 12, 2501. doi: 10.1038/s41467-021-22702-2
Keywords: inland freshwater, ecosystem, catchment, greenhouse gas fluxes, CO2, CH4, N2O
Citation: Piatka DR, Barth JAC and Kiese R (2024) Editorial: Greenhouse gas emissions from terrestrial freshwater ecosystems: spatial and temporal hot spots. Front. Water 6:1390123. doi: 10.3389/frwa.2024.1390123
Received: 22 February 2024; Accepted: 15 March 2024;
Published: 26 March 2024.
Edited and reviewed by: Richard Graham Taylor, University College London, United Kingdom
Copyright © 2024 Piatka, Barth and Kiese. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: David R. Piatka, d_piatka@yahoo.de