Rotenberg et al. (2025) Evapotranspiration saturation amplifies climate sensitivity of terrestrial water yield

Identification

• Journal: Nature Communications
• Year: 2025
• Date: 2025-11-23
• Authors: Eyal Rotenberg, Fyodor Tatarinov, Jonathan Müller, Dan Yakir
• DOI: 10.1038/s41467-025-66570-6

Research Groups

• Earth and Planetary Sciences, The Weizmann Institute of Science, Rehovot, Israel
• School for Climate Studies, Stellenbosch University, Stellenbosch, South Africa

Short Summary

This study reveals that ecosystem evapotranspiration (ET) saturates at approximately 480 mm per year globally, which significantly amplifies the sensitivity of terrestrial water yield (WY) to precipitation variability, increasing climate change risks for ecosystems and society.

Objective

• To assess if ecosystem evapotranspiration (ET) exhibits a global saturation limit, and consequently, if terrestrial water yield (WY) shows an amplified sensitivity to precipitation variability under climate change, challenging traditional hydrological models.

Study Configuration

• Spatial Scale: Global land areas, covering various biomes and climates, with analysis at biome and individual eddy covariance site levels.
• Temporal Scale: Multi-year annual averages (up to 20 years of continuous measurements), historical periods (1850–2014), and future projections (2080–2099) under the SSP5-8.5 scenario.

Methodology and Data

• Models used:
  • Budyko equation
  • Penman-Monteith equation (FAO-PM method for potential ET)
  • Priestley-Taylor equation
  • Coupled Model Intercomparison Project Phase 6 (CMIP6) Earth System Models (27 models)
• Data sources:
  • Global eddy covariance (EC) flux stations from FLUXNET, AmeriFlux, EuroFlux, and AsiaFlux databases (1041 ET data years across 185 globally distributed sites).
  • Specific long-term sites in Israel (Yatir forest, Kadita, Birya).
  • Observed variables: Evapotranspiration (ET), precipitation (P), gross primary production (GPP), latent heat of evaporation (LE), net radiation (Rn), air temperature (Ta), water vapor pressure deficit (VPD).
  • CMIP6 model outputs for monthly precipitation and evaporation over land.

Main Results

• Observed ecosystem evapotranspiration (ET) exhibits an apparent 'saturation' limit of approximately 480 ± 210 mm per year across diverse climates and biomes, significantly below values predicted by Budyko-type energy- and supply-driven models.
• This ET saturation is mechanistically linked to the physiological coupling between transpiration and photosynthesis, where photosynthetic capacity limits stomatal conductance and thus transpiration, even with increasing water or energy availability.
• Terrestrial water yield (WY = P - ET) responds approximately linearly to precipitation (P) across the full precipitation range (R² > 0.8 in most cases), demonstrating a striking sensitivity.
• Small changes in precipitation lead to disproportionately large impacts on WY; for example, a ~40% decline in P can result in nearly a 100% reduction in WY in dry regions.
• The global average precipitation threshold for zero water yield (WYP=0) is 371 ± 88 mm per year, consistent with the observed ET saturation point.
• CMIP6 model projections corroborate these findings, showing that a 21% decrease in P leads to an ~87% decline in WY (a four-fold amplification) in drying regions, while a 21% increase in P yields a ~44% increase in WY (a two-fold amplification) in wetter regions.
• Site-level analysis confirms the high sensitivity of WY to P and highlights the significant impact of land cover type on the sustainability limit (WYP=0 values).

Contributions

• Challenges the fundamental assumption of traditional hydrological models (e.g., Budyko framework) that ET continuously increases with available water and energy, by providing robust observational evidence of a global ET saturation limit.
• Establishes water yield (WY) as a more sensitive and integrative indicator of climate change impacts on terrestrial water resources, demonstrating its amplified response to precipitation variability compared to precipitation itself.
• Provides a mechanistic explanation for ET saturation rooted in ecophysiological regulation (carbon-water coupling and GPP saturation), advancing the understanding of ecosystem water dynamics beyond purely physical constraints.
• Offers critical implications for climate change adaptation and water management strategies, highlighting increased flood risk in wet regions and accelerated ecosystem/societal sustainability limits in dry regions due to this amplified sensitivity.

Funding

• Israel Science Foundation (ISF BRG grant 2481/22)
• KKL
• Institute for Environmental Sustainability (IES)
• Kimmel and de Bottom Centers at the Weizmann Institute of Science
• Swiss National Science Foundation (Postdoc.Mobility stipend for J.D. Muller)
• Society of Swiss Friends of the Weizmann Institute (fellowship for J.D. Muller)

Citation

@article{Rotenberg2025Evapotranspiration,
  author = {Rotenberg, Eyal and Tatarinov, Fyodor and Müller, Jonathan and Yakir, Dan},
  title = {Evapotranspiration saturation amplifies climate sensitivity of terrestrial water yield},
  journal = {Nature Communications},
  year = {2025},
  doi = {10.1038/s41467-025-66570-6},
  url = {https://doi.org/10.1038/s41467-025-66570-6}
}