Pang et al. (2025) Flash droughts threaten global managed forests

Identification

• Journal: Nature Communications
• Year: 2025
• Date: 2025-12-10
• Authors: Jianzhuang Pang, Hang Xu, Yang Xu, Yifan Zhang, Xiaoyun Wu, Kexin Li, Zhiqiang Zhang
• DOI: 10.1038/s41467-025-66021-2

Research Groups

• Jixian National Forest Ecosystem Observation and Research Station, CNERN, Beijing Forestry University, Beijing, P.R. China
• Key Laboratory of Soil and Water Conservation and Desertification Combating, State Forestry and Grassland Administration, Beijing, P.R. China
• School of Soil and Water Conservation, Beijing Forestry University, Beijing, P.R. China

Short Summary

This study reveals that global forests, particularly managed ones, have experienced increasingly rapid, intense, and prolonged flash droughts over the past four decades, with current forest management practices exacerbating their vulnerability to browning.

Objective

• To quantify global forest responses to flash droughts and analyze the effects of multiple regulating factors, specifically investigating the spatiotemporal patterns of flash drought characteristics, identifying key regulatory factors using an interpretable machine learning framework, and assessing the influence of forest management practices.

Study Configuration

• Spatial Scale: Global, with a spatial resolution of 0.1 degrees.
• Temporal Scale: Past four decades (approximately 1982–2022 for flash drought characteristics; 1979–2018 for forest responses and regulating factors).

Methodology and Data

• Models used: Interpretable machine learning framework (XGBoost model), Shapley Additive Explanations framework.
• Data sources:
  • Reconstructed global high spatiotemporal resolution Standardized Precipitation-Evapotranspiration Index (gSPEI-HR, 0.1°, daily) derived from ERA5-Land.
  • Hourly potential evapotranspiration (hPET) dataset calculated using the Penman-Monteith method.
  • Bi-monthly PKU GIMMS Normalized Difference Vegetation Index (NDVI) product (1982–2022).
  • GLOBMAP Leaf Area Index (LAI) data (1982–2019).
  • Global Observing Satellite Initiative for Fluorescence (GOSIF) Solar-Induced Chlorophyll Fluorescence (SIF) data (2000–2022).
  • MODIS Land Cover Dynamics product (MCD12Q2) for growing seasons.
  • Global fine-scale forest composition map (2015) for intact and managed forests.
  • Global 30 m Land-Cover Dynamic Monitoring Product with a Fine Classification System (GLC_FCS30D).
  • Forest traits: Canopy height, maximum rooting depth, tree density, and forest age from various global datasets.
  • Systematic meta-analysis of scientific literature on forest management practices.

Main Results

• Global forests have experienced increasingly rapid, intense, and prolonged flash droughts over the past four decades.
• Flash droughts caused browning (ΔNDVI < 0) in 42.73% of global forests.
• Managed forests are more susceptible to browning from flash droughts (mean ΔNDVI = −0.11) compared to intact forests, due to limited acclimation capacity to rapid drought stress driven by extreme heat.
• Forest management (18.37%) was identified as the primary factor influencing spatial variations in ΔNDVI, followed by mean annual temperature (12.07%), temperature anomalies (10.30%), and stress duration (9.98%).
• Forest resilience to flash droughts generally increases with forest age and canopy height (up to a certain threshold).
• NDVI declines are more prevalent in forests located in regions with higher mean annual temperatures and lower mean annual precipitation.
• Prolonged flash droughts significantly exacerbate forest browning; intact forests show resilience in later stages, while managed forests experience greater declines during prolonged events (stress duration > 8 pentads).
• Current forest management practices, such as logging (especially clear-cuts) and fertilization, exacerbate the vulnerability of managed forests to flash droughts, while thinning can have negative impacts. Agroforestry showed the largest NDVI reductions (ΔNDVI = −0.29) among managed forest types.

Contributions

• Provides a global consensus on forest responses to flash droughts, addressing previous inconsistencies in the literature.
• Developed and utilized a global high spatiotemporal resolution Standardized Precipitation-Evapotranspiration Index (gSPEI-HR) dataset for precise flash drought identification.
• Applied an interpretable machine learning framework to identify key regulating factors and their interactive effects on global forest responses to flash droughts.
• Quantified the critical role of forest management practices in modulating forest vulnerability to flash droughts at a global scale.
• Underscores the urgent need for adaptive forest management strategies that integrate resistance and resilience to extreme climatic events.

Funding

• National Key Research and Development Program of China (Grant No. 2022YFF1302501)
• Fundamental Research Funds for the Central Universities (Grant No. JCYJ202507)
• National Natural Science Foundation of China (Grant Nos. 32301664, 32271967)
• Young Elite Scientist Sponsorship Program by Cast (Grant No. YESS20230091)

Citation

@article{Pang2025Flash,
  author = {Pang, Jianzhuang and Xu, Hang and Xu, Yang and Zhang, Yifan and Wu, Xiaoyun and Li, Kexin and Zhang, Zhiqiang},
  title = {Flash droughts threaten global managed forests},
  journal = {Nature Communications},
  year = {2025},
  doi = {10.1038/s41467-025-66021-2},
  url = {https://doi.org/10.1038/s41467-025-66021-2}
}