EGU General Assembly 2022
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Towards a green water planetary boundary

Lan Wang-Erlandsson1, Arne Tobian1,2, Ruud van der Ent3, Ingo Fetzer1, Sofie te Wierik4, Miina Porkka5,6, Arie Staal1,7, Fernando Jaramillo8, Heindriken Dahlmann1,9, Chandrakant Singh1, Peter Greve10, Dieter Gerten2,11, Patrick Keys12, Tom Gleeson13, Sarah Cornell1, Will Steffen14, Xuemei Bai14, and Johan Rockström1,2
Lan Wang-Erlandsson et al.
  • 1Stockholm Resilience Centre, Stockholm University, Sweden.
  • 2Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany.
  • 3Delft University of Technology, Delft, the Netherlands
  • 4University of Amsterdam, Amsterdam, the Netherlands
  • 5Aalto University, Espoo, Finland
  • 6Global Economic Dynamics and the Biosphere Programme, Royal Swedish Academy of Sciences, Stockholm, Sweden
  • 7Utrecht University, Utrecht, the Netherlands
  • 8Department of Physical Geography, Stockholm University, Stockholm, Sweden
  • 9Albert-Ludwigs-Universität Freiburg, Freiburg im Breisgau, Germany
  • 10The International Institute for Applied Systems Analysis, Vienna, Austria
  • 11Geography Department, Humboldt-Universität zu Berlin, Germany
  • 12Colorado State University, Fort Collins, CO, United States
  • 13University of Victoria, Victoria, BC, Canada
  • 14The Australian National University, Canberra, ACT, Australia

Green water - i.e., land precipitation, evaporation and soil moisture - is fundamental for the functioning of the biosphere and the Earth System, but is increasingly perturbed by continental-to-planetary scale human pressures on land, water and climate systems. The planetary boundaries (PB) framework demarcates a global safe operating space for humanity, but does hitherto not explicitly account for green water. Here, we propose a green-water boundary within the existing PB framework, of which a control variable could be defined as "the percentage of ice-free land area on which root-zone soil moisture deviates from Holocene variability for any month of the year". We provide provisional estimates of baseline departures based on CMIP6 data, and review the literature on soil-moisture induced deterioration in Earth System functioning. The evidences taken together suggest that the green water PB is already transgressed, implying that human modifications of green water need to come to a halt and be reversed. Future research needs to advance our understanding of root-zone water dynamics, including associated large-scale and potentially non-linear interactions with ecohydrology, hydroclimate, biogeochemistry and societies.

How to cite: Wang-Erlandsson, L., Tobian, A., van der Ent, R., Fetzer, I., te Wierik, S., Porkka, M., Staal, A., Jaramillo, F., Dahlmann, H., Singh, C., Greve, P., Gerten, D., Keys, P., Gleeson, T., Cornell, S., Steffen, W., Bai, X., and Rockström, J.: Towards a green water planetary boundary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12865,, 2022.