Integrating the evidence for a terrestrial carbon sink caused by increasing atmospheric CO2

Anthony P. Walker*, Martin G. De Kauwe, Ana Bastos, Soumaya Belmecheri, Katerina Georgiou, Ralph F. Keeling, Sean M. McMahon, Belinda E. Medlyn, David J.P. Moore, Richard J. Norby, Sönke Zaehle, Kristina J. Anderson-Teixeira, Giovanna Battipaglia, Roel J.W. Brienen, Kristine G. Cabugao, Maxime Cailleret, Elliott Campbell, Josep G. Canadell, Philippe Ciais, Matthew E. CraigDavid S. Ellsworth, Graham D. Farquhar, Simone Fatichi, Joshua B. Fisher, David C. Frank, Heather Graven, Lianhong Gu, Vanessa Haverd, Kelly Heilman, Martin Heimann, Bruce A. Hungate, Colleen M. Iversen, Fortunat Joos, Mingkai Jiang, Trevor F. Keenan, Jürgen Knauer, Christian Körner, Victor O. Leshyk, Sebastian Leuzinger, Yao Liu, Natasha MacBean, Yadvinder Malhi, Tim R. McVicar, Josep Penuelas, Julia Pongratz, A. Shafer Powell, Terhi Riutta, Manon E.B. Sabot, Juergen Schleucher, Stephen Sitch

*Corresponding author for this work

Research output: Contribution to journalReview article (Academic Journal)peer-review

27 Citations (Scopus)

Abstract

Atmospheric carbon dioxide concentration ([CO2]) is increasing, which increases leaf-scale photosynthesis and intrinsic water-use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter; transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO2] increase and thus climate change. However, ecosystem CO2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO2]-driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO2] (iCO2) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre-industrial times. Established theory, supported by experiments, indicates that iCO2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO2, albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change.

Original languageEnglish
Pages (from-to)2413-2445
Number of pages33
JournalNew Phytologist
Volume229
Issue number5
Early online date12 Aug 2020
DOIs
Publication statusPublished - Mar 2021

Bibliographical note

Funding Information:
This paper was outlined and informed by the ‘Integrating CO‐fertilization evidence streams and theory (ICOFEST)’ meeting held at Biosphere II in September 2018. The meeting was supported by the US Department of Energy Office of Science, Biological and Environmental Research through the Free Air CO Enrichment Model Data Synthesis (FACE‐MDS) project. ORNL is managed by UT‐Battelle, LLC, for the DOE under contract DE‐AC05‐00OR22725. MGDK acknowledges support from Australian Research Council (ARC) Discovery Grant (DP190101823). DJPM and WKS acknowledge support from NASA Terrestrial Ecosystems Grant 80NSSC19M0103. SZ received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 647204). KJAT acknowledges support from the Smithsonian's Forest Global Earth Observatory (ForestGEO). JBF contributed to this research at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration with support from the NASA IDS program. VH acknowledges support from the Earth Systems and Climate Change Hub, funded by the Australian Research Council. FJ acknowledges support by the Swiss NSF (no. 200020_172476). TFK was supported by the NASA Terrestrial Ecology Program IDS Award NNH17AE86I. PC and JP were supported by the European Research Council Synergy grant ERC‐2013‐SyG‐2013‐610028 IMBALANCE‐P. J. Pongratz was supported by the German Research Foundation’s Emmy Noether Program. MEBS acknowledges support from the Australian Research Council Centre of Excellence for Climate Extremes (CE170100023). JS acknowledges support from VR, KAW and Kempe foundations. CT was supported by a Lawrence Fellow award through Lawrence Livermore National Laboratory (LLNL) under contract DE‐AC52‐07NA27344 with the US Department of Energy and the LLNL‐LDRD Program under Project No. 20‐ERD‐055. MST was supported by the US Department of Energy, Office of Science under contract number DE‐AC02‐05CH11231. ATT acknowledges funding from the USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Programme grant no. 2018‐67012‐31496 and the University of California Laboratory Fees Research Program Award No. LFR‐20‐652467. SLV was supported by the US National Science Foundation Paleo Perspectives on Climate Change Program. PvM was supported by the US Geological Survey Ecosystems Mission Area. Government sponsorship is acknowledged. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government. 2 2

Funding Information:
This paper was outlined and informed by the ?Integrating CO2-fertilization evidence streams and theory (ICOFEST)? meeting held at Biosphere II in September 2018. The meeting was supported by the US Department of Energy Office of Science, Biological and Environmental Research through the Free Air CO2 Enrichment Model Data Synthesis (FACE-MDS) project. ORNL is managed by UT-Battelle, LLC, for the DOE under contract DE-AC05-00OR22725. MGDK acknowledges support from Australian Research Council (ARC) Discovery Grant (DP190101823). DJPM and WKS acknowledge support from NASA Terrestrial Ecosystems Grant 80NSSC19M0103. SZ received funding from the European Research Council (ERC) under the European Union?s Horizon 2020 research and innovation programme (grant agreement no. 647204). KJAT acknowledges support from the Smithsonian's Forest Global Earth Observatory (ForestGEO). JBF contributed to this research at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration with support from the NASA IDS program. VH acknowledges support from the Earth Systems and Climate Change Hub, funded by the Australian Research Council. FJ acknowledges support by the Swiss NSF (no. 200020_172476). TFK was supported by the NASA Terrestrial Ecology Program IDS Award NNH17AE86I. PC and JP were supported by the European Research Council Synergy grant ERC-2013-SyG-2013-610028 IMBALANCE-P. J. Pongratz was supported by the German Research Foundation?s Emmy Noether Program. MEBS acknowledges support from the Australian Research Council Centre of Excellence for Climate Extremes (CE170100023). JS acknowledges support from VR, KAW and Kempe foundations. CT was supported by a Lawrence Fellow award through Lawrence Livermore National Laboratory (LLNL) under contract DE-AC52-07NA27344 with the US Department of Energy and the LLNL-LDRD Program under Project no. 20-ERD-055. MST was supported by the US Department of Energy, Office of Science under contract number DE-AC02-05CH11231. ATT acknowledges funding from the USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Programme grant no. 2018-67012-31496 and the University of California Laboratory Fees Research Program Award no. LFR-20-652467. SLV was supported by the US National Science Foundation Paleo Perspectives on Climate Change Program. PvM was supported by the US Geological Survey Ecosystems Mission Area. Government sponsorship is acknowledged. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government.

Publisher Copyright:
© 2020 The Authors New Phytologist Foundation © 2020 New Phytologist

Keywords

  • beta factor
  • carbon dioxide
  • CO fertilization
  • CO-fertilization hypothesis
  • free-air CO enrichment (FACE)
  • global carbon cycle
  • land–atmosphere feedback
  • terrestrial ecosystems

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