Greening drylands despite warming consistent with carbon dioxide fertilization effect

Alemu Gonsamo, Philippe Ciais, Diego G. Miralles, Stephen Sitch, Wouter Dorigo, Danica Lombardozzi, Pierre Friedlingstein, Julia E.M.S. Nabel, Daniel S. Goll, Michael O'Sullivan, Almut Arneth, Peter Anthoni, Atul K. Jain, Andy Wiltshire, Philippe Peylin, Alessandro Cescatti

Research output: Contribution to journalArticlepeer-review


The rising atmospheric CO2 concentration leads to a CO2 fertilization effect on plants—that is, increased photosynthetic uptake of CO2 by leaves and enhanced water-use efficiency (WUE). Yet, the resulting net impact of CO2 fertilization on plant growth and soil moisture (SM) savings at large scale is poorly understood. Drylands provide a natural experimental setting to detect the CO2 fertilization effect on plant growth since foliage amount, plant water-use and photosynthesis are all tightly coupled in water-limited ecosystems. A long-term change in the response of leaf area index (LAI, a measure of foliage amount) to changes in SM is likely to stem from changing water demand of primary productivity in water-limited ecosystems and is a proxy for changes in WUE. Using 34-year satellite observations of LAI and SM over tropical and subtropical drylands, we identify that a 1% increment in SM leads to 0.15% (±0.008, 95% confidence interval) and 0.51% (±0.01, 95% confidence interval) increments in LAI during 1982‒1998 and 1999‒2015, respectively. The increasing response of LAI to SM has contributed 7.2% (±3.0%, 95% confidence interval) to total dryland greening during 1999‒2015 compared to 1982‒1998. The increasing response of LAI to SM is consistent with the CO2 fertilization effect on WUE in water-limited ecosystems, indicating that a given amount of SM has sustained greater amounts of photosynthetic foliage over time. The LAI responses to changes in SM from seven dynamic global vegetation models are not always consistent with observations, highlighting the need for improved process knowledge of terrestrial ecosystem responses to rising atmospheric CO2 concentration.

Original languageEnglish (US)
Pages (from-to)3336-3349
Number of pages14
JournalGlobal change biology
Issue number14
StatePublished - Jul 2021


  • CO fertilization effect
  • dryland greening
  • dynamic global vegetation model
  • leaf area index
  • satellite soil moisture
  • water-use efficiency

ASJC Scopus subject areas

  • General Environmental Science
  • Global and Planetary Change
  • Ecology
  • Environmental Chemistry


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