Giardina et al. (2026) Groundwater regulates the spatial pattern of photosynthesis in the contiguous United States

Identification

• Journal: Communications Earth & Environment
• Year: 2026
• Date: 2026-09-26
• Authors: Francesco Giardina, Jiangong Liu, Sonia Isabelle Seneviratne, Benjamin David Stocker, Pierre Gentine
• DOI: 10.1038/s43247-026-04067-w

Research Groups

• Institute for Atmospheric and Climate Science, Department of Environmental Systems Science, ETH Zurich
• Department of Earth and Environmental Engineering, Columbia University
• Carbon Neutrality and Climate Change Thrust, Society Hub, The Hong Kong University of Science and Technology (Guangzhou)
• Institute of Geography, University of Bern
• Oeschger Centre for Climate Change Research, University of Bern
• Center for Learning the Earth with Artificial Intelligence and Physics (LEAP), Columbia University

Short Summary

This study investigates the role of groundwater in regulating photosynthesis in the contiguous United States, using satellite observations and model estimates. The results show that groundwater accounts for 48 to 101% of the effect attributed to aridity in modulating forest photosynthesis.

Objective

• Investigate the relative contribution of groundwater and aridity to spatial variation in mean annual photosynthesis in the contiguous United States

Study Configuration

• Spatial Scale: Continental (contiguous United States)
• Temporal Scale: Annual

Methodology and Data

• Models used: Causality-guided explainable machine learning
• Data sources: Satellite observations of solar-induced fluorescence, model estimates of water table depth and aridity

Main Results

• Groundwater accounts for 48 to 101% of the effect attributed to aridity in modulating forest photosynthesis across the contiguous United States.
• The relative importance of groundwater compared to aridity remains substantial in savannahs and shrublands (30-58%), grasslands (22-42%), and croplands (15-32%).

Contributions

• This study provides new insights into the role of groundwater in regulating photosynthesis, highlighting its significant contribution to spatial variation in mean annual photosynthesis.

Funding

• Swiss National Science Foundation (grant no. PCEFP2_181115)
• LEMONTREE project (Land Ecosystem Models based on New Theory, Observation, and Experiments), funded through the generosity of Eric and Wendy Schmidt
• USMILE European Research Council Synergy Grant
• Learning the Earth with Artificial Intelligence and Physics (LEAP) Science and Technology Center, funded by the National Science Foundation (Award #2019625-STC)
• Open access funding provided by Swiss Federal Institute of Technology Zurich

Citation

@article{Giardina2026Groundwater,
  author = {Giardina, Francesco and Liu, Jiangong and Seneviratne, Sonia Isabelle and Stocker, Benjamin David and Gentine, Pierre},
  title = {Groundwater regulates the spatial pattern of photosynthesis in the contiguous United States},
  journal = {Communications Earth & Environment},
  year = {2026},
  doi = {10.1038/s43247-026-04067-w},
  url = {https://doi.org/10.1038/s43247-026-04067-w}
}