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, William K. Smith, Benjamin Sulman, Benton Taylor, César Terrer, Margaret S. Torn, Kathleen K. Treseder, Anna T. Trugman, Susan E. Trumbore, Phillip J. van Mantgem, Steve L. Voelker, Mary E. Whelan, Pieter A. Zuidema

Research output: Contribution to journalReview articlepeer-review

283 Scopus citations


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 (US)
Pages (from-to)2413-2445
Number of pages33
JournalNew Phytologist
Issue number5
StatePublished - Mar 2021


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

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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