Chen et al. (2026) Emergent constraints on the hydrological impacts of land use and land cover change

Identification

• Journal: Nature Communications
• Year: 2026
• Date: 2026-02-18
• Authors: Zefeng Chen, Alessandro Cescatti, Ruofei Xing, Giovanni Forzieri
• DOI: 10.1038/s41467-026-69883-2

Research Groups

• Department of Civil and Environmental Engineering, University of Florence, Florence, Italy
• European Commission, Joint Research Centre, Ispra, Italy
• National Key Laboratory of Water Disaster Prevention, Hohai University, Nanjing, China
• Business School, Hohai University, Nanjing, China

Short Summary

This study applies an observation-based emergent constraint framework to correct Earth system model (ESM) estimates of evapotranspiration changes due to land use and land cover changes (LULCC), revealing significant biases in unconstrained models and projecting stronger evapotranspiration enhancements in future afforestation scenarios.

Objective

• To address the substantial disagreement among state-of-the-art Earth system models regarding the sign and magnitude of terrestrial evapotranspiration changes induced by land use and land cover changes (LULCC) at global and regional scales.
• To develop and apply a hierarchical emergent constraint framework using the observation-based transpiration-specific Bowen ratio to improve the accuracy of modelled hydrological impacts of LULCC.

Study Configuration

• Spatial Scale: Global and regional (specifically Central and South America, tropics, and subtropics).
• Temporal Scale: Historical impacts of LULCC and future afforestation scenarios.

Methodology and Data

• Models used: State-of-the-art Earth system models (ESMs), including those contributing to CMIP6, within a multi-model ensemble and emergent constraint framework.
• Data sources:
  • Observation-based transpiration-specific Bowen ratio.
  • Publicly available datasets, including land use harmonization data (LUH2), reanalysis data (ERA5-Land), satellite-based land surface evaporation products (e.g., GLEAM), and eddy covariance data (FLUXNET).
  • Custom MATLAB (R2024a) codes for data analysis.

Main Results

• The emergent constraint, derived from the observation-based transpiration-specific Bowen ratio, significantly corrects modelled evapotranspiration (ET) changes induced by LULCC.
• This constraint reverses the sign of the original model estimates for ET changes at the global scale and over Central and South America.
• It substantially narrows the inter-model spread in ET projections, reducing uncertainty.
• The primary source of bias in unconstrained models is identified as the misrepresentation of the transpiration-specific Bowen ratio and its variations across different plant functional types.
• When applied to a future afforestation scenario, the constrained simulations project stronger ET enhancements and weaker decreases in terrestrial water availability compared to the original simulations, particularly in tropical and subtropical regions.

Contributions

• Introduces a novel emergent constraint framework that effectively reduces uncertainty in Earth system model projections of LULCC hydrological impacts.
• Provides a critical correction to the sign and magnitude of modelled evapotranspiration changes due to LULCC, improving the reliability of future climate projections.
• Identifies a key model deficiency: the misrepresentation of the transpiration-specific Bowen ratio and its variability across plant functional types.
• Offers refined and more optimistic projections for terrestrial water availability under future afforestation scenarios, particularly in water-stressed regions.

Funding

• European Union’s Horizon Europe research and innovation programme under the Marie Skłodowska-Curie Actions (grant agreement No. 101152010, TYPIC).
• European Union’s Horizon Europe research and innovation programme under grant agreement No. 101137601 (ClimTip project).
• Fundamental Research Funds for the Central Universities (grant agreement No. B240207078).
• China Scholarship Council (CSC) Grant (grant agreement No. 202406710180).

Citation

@article{Chen2026Emergent,
  author = {Chen, Zefeng and Cescatti, Alessandro and Xing, Ruofei and Forzieri, Giovanni},
  title = {Emergent constraints on the hydrological impacts of land use and land cover change},
  journal = {Nature Communications},
  year = {2026},
  doi = {10.1038/s41467-026-69883-2},
  url = {https://doi.org/10.1038/s41467-026-69883-2}
}