A planetary boundary for green water

Lan Wang-Erlandsson*, Arne Tobian, Ruud J. van der Ent, Ingo Fetzer, Sofie te Wierik, Miina Porkka, Arie Staal, Fernando Jaramillo, Heindriken Dahlmann, Chandrakant Singh, Peter Greve, Dieter Gerten, Patrick W. Keys, Tom Gleeson, Sarah E. Cornell, Will Steffen, Xuemei Bai, Johan Rockström

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review


Green water — terrestrial precipitation, evaporation and soil moisture — is fundamental to Earth system dynamics and is now extensively perturbed by human pressures at continental to planetary scales. However, green water lacks explicit consideration in the existing planetary boundaries framework that demarcates a global safe operating space for humanity. In this Perspective, we propose a green water planetary boundary and estimate its current status. The green water planetary boundary can be represented by the percentage of ice-free land area on which root-zone soil moisture deviates from Holocene variability for any month of the year. Provisional estimates of departures from Holocene-like conditions, alongside evidence of widespread deterioration in Earth system functioning, indicate that the green water planetary boundary is already transgressed. Moving forward, research needs to address and account for the role of root-zone soil moisture for Earth system resilience in view of ecohydrological, hydroclimatic and sociohydrological interactions.
Original languageEnglish
Pages (from-to)380-392
Number of pages13
JournalNature Reviews Earth and Environment
Issue number6
Early online date2022
Publication statusPublished - Jun 2022


  • Governance
  • Hydorlogy
  • Water resources


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