Yan et al. (2026) Divergent hydrological responses to restoration between planted and natural forests basins in drylands

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2026
• Date: 2026-01-06
• Authors: Ying Yan, Xiaogang Li, Fernando Jaramillo, Xiaohong CHEN, Xin Lan, Linyin Cheng
• DOI: 10.1016/j.ejrh.2025.103047

Research Groups

• Center for Water Resources and Environment, School of Civil Engineering, Sun Yat-sen University, Guangzhou, Guangdong, China
• Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, Guangdong, China
• Department of Physical Geography and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
• Department of Geosciences, University of Arkansas, Fayetteville, AR, USA

Short Summary

This study investigates the divergent basin-scale water yield responses to forest expansion in planted versus natural forests in global drylands. It finds that planted forests lead to significantly greater reductions in water yield compared to natural forests, primarily due to larger changes in underlying surface parameters rather than climate change.

Objective

• To determine how planted forest (PF) and natural forest (NF) basins differ in their water-yield responses to ecological restoration.
• To identify the mechanisms driving these differences in hydrological responses.
• To ascertain under which climatic conditions afforestation might avoid adverse hydrological impacts.

Study Configuration

• Spatial Scale: Global arid and semi-arid regions, analyzing 6356 natural forest basins and 1231 planted forest basins.
• Temporal Scale: Data collected from 1995 to 2019, with analysis periods defined as Period I (1995–2004) and Period II (2010–2019) for decadal-scale hydrological response detection.

Methodology and Data

• Models used:
  • Budyko framework (Budyko-Fu equation) for attributing water yield changes to climate and land surface changes.
  • Penman–Monteith equation and Hamon’s method for potential evapotranspiration (PET) estimation.
  • Water-energy partitioning approach (for robustness verification).
• Data sources:
  • Forest Management: Global Forest Management Data (GFMD) (100 m resolution, 2015) for differentiating planted and natural forests; Global Forest Cover Change (GFCC) (30 m resolution, 2000-2015) for forest cover changes.
  • Basin Boundaries: HydroSHEDS dataset (level 7).
  • Climate Data: Terraclimate database for precipitation (P) and PET; ERA5 reanalysis data for PET (robustness check).
  • Hydrological Data: Globally integrated actual evapotranspiration (AET) product by Elnashar et al. (2021) (monthly, 1 km resolution, 1982-2019); MODIS AET products (robustness check). Runoff (R) estimated from P - AET, assuming negligible long-term water storage change. Runoff observations from literature for validation.

Main Results

• Long-term average water yields in planted forest (PF) basins are 3–12% less than in natural forest (NF) basins.
• Following forest expansion, the reduction in water yield is approximately 10% greater in PF basins (20% decline) compared to NF basins (10% decline).
• Attribution analysis indicates that land surface changes (represented by the Budyko parameter 'm') are the primary contributor to water yield decrease in both PF (94% contribution) and NF (83% contribution) basins, with climate change having a minor role.
• PF basins exhibit a substantially larger underlying contribution to water yield decrease, characterized by greater changes in the underlying surface parameter 'm' and increased sensitivity of water yield to 'm' and aridity index (P/PET) after restoration.
• In PF basins, the underlying-related water yield changes are mainly dominated by changes in water yield sensitivity to parameter 'm' (indirect effect), whereas in NF basins, they are dominated by direct changes in parameter 'm'.
• The variability of water yield (coefficient of variation of R/P) is lower in PF basins than in NF basins, but the gap in water yield sensitivities between the two forest types widened significantly in later periods (2011–2015).
• Negative hydrological impacts in PF basins are most pronounced in water-limited regions (aridity index P/PET < 1) and are mitigated in water-sufficient regions (P/PET > 1).

Contributions

• Provides a global, large-scale, and multi-decadal assessment using remote sensing data to distinguish and quantify the divergent hydrological responses of planted versus natural forests to restoration in drylands, addressing a gap in existing literature.
• Identifies that ecosystem complexity and structural differences (e.g., rooting depth, water-use efficiency) between planted and natural forests are key mechanisms driving the observed hydrological differences.
• Offers practical guidance for policymakers on optimal locations for afforestation, suggesting prioritization of humid regions (P/PET > 1) and careful evaluation in moderately dry regions (0.5 < P/PET < 1) to minimize adverse hydrological impacts.
• Emphasizes the importance of forest management strategies and the quality of planted trees in achieving sustainable ecological restoration outcomes.

Funding

• National Natural Science Foundation of China (52179031)
• National Key R&D Program of China (2021YFC3001000)
• Natural Science Foundation of Guangdong Province (2023B1515020116)
• Guangdong Basic and Applied Basic Research Foundation (2023B1515040028)
• Guangdong Provincial Department of Science and Technology (2019ZT08G090)

Citation

@article{Yan2026Divergent,
  author = {Yan, Ying and Li, Xiaogang and Jaramillo, Fernando and CHEN, Xiaohong and Lan, Xin and Cheng, Linyin},
  title = {Divergent hydrological responses to restoration between planted and natural forests basins in drylands},
  journal = {Journal of Hydrology Regional Studies},
  year = {2026},
  doi = {10.1016/j.ejrh.2025.103047},
  url = {https://doi.org/10.1016/j.ejrh.2025.103047}
}