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

Diverging simulated effects of future drought stress on the Amazon rainforest 

Phillip Papastefanou1,2, Thomas Pugh1, Allan Buras2, Annemarie Eckes-Shephard1, Katrin Fleischer3, Thorsten Grams2, Konstantin Gregor2, Thomas Hickler4, Andreas Krause2, David Lapola5, Daijun Liu6, Christian Zang7, and Anja Rammig2
Phillip Papastefanou et al.
  • 1Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden
  • 2Technical University of Munich, Germany
  • 3Max Planck Institute for Biogeochemistry, Jena, Germany
  • 4Senckenberg Biodiversity and Climate Research Centre (BiK-F), Frankfurt/Main, Germany
  • 5University of Campinas – UNICAMP, Campinas, Brazil
  • 6University of Vienna, Vienna, Austria
  • 7Weihenstephan-Triesdorf University of Applied Sciences, Freising, Germany

The Amazon rainforest is the largest intact tropical forest ecosystem and stores about 120 Pg of carbon. To this day, it acts as a carbon sink by taking up carbon from the atmosphere, however, long-term observations show a decline in strength of this carbon sink, a trend that at current rates would likely lead to the Amazon basin becoming a carbon source around year 2050. The reasons for this declining trend are disputed, increasing temperatures and more frequent and intense droughts are becoming the potential drivers. Vegetation modelling offers a possibility to disentangle the effects of these drivers, however, most Dynamic Global Vegetation Models (DGVMs) or Earth System Models (ESMs) are still not able to reproduce this observed carbon sink decline and the correct response of vegetation to drought stress. Here, we apply a new version of the DGVM LPJ-GUESS with improved plant hydraulics. It is one of the few state-of-the-art DGVMs that can successfully (1) capture the carbon dynamics under severe drought stress and (2) reproduce the current observed declining trend of the carbon sink. We investigate whether the Amazon rainforest will recover its sink strength or turn into a carbon when driven by climate projection source from the latest Inter-Sectoral Impact Model Intercomparison Project (ISIMIP 3a), using multiple forcing datasets. The simulations show strongly diverging response patterns of the Amazon rainforest that depend on both the selected emission scenario (e.g. SSP5-8.5 or 1-2.6) and the climate model (e.g. UKESM vs. ESM4). Using the SSP5-8.5 scenarios we find higher drought-induced carbon losses in the second half of the 21st century compared to the first half of the century. However, these losses are partly (e.g. ESM4) or completely (e.g. UKESM) outweighed by higher carbon gains induced by higher CO2 concentrations. Our findings highlight the complex interplay of CO2 fertilization, higher atmospheric dryness (more negative vapour pressure deficit) and its effects on stomatal conductance. 

How to cite: Papastefanou, P., Pugh, T., Buras, A., Eckes-Shephard, A., Fleischer, K., Grams, T., Gregor, K., Hickler, T., Krause, A., Lapola, D., Liu, D., Zang, C., and Rammig, A.: Diverging simulated effects of future drought stress on the Amazon rainforest , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12669,, 2022.