Chai et al. (2025) Flash droughts exacerbate global vegetation loss and delay recovery

Identification

• Journal: Nature Communications
• Year: 2025
• Date: 2025-12-08
• Authors: Yuanfang Chai, Chiyuan Miao, Amir AghaKouchak, Yadu Pokhrel, Yongshuo H. Fu, Xiaoyan Li, Jiachen Ji, Qi Zhang, Josep Peñuelas
• DOI: 10.1038/s41467-025-67173-x

Research Groups

• State Key Laboratory of Earth Surface Processes and Disaster Risk Reduction, Faculty of Geographical Science, Beijing Normal University, Beijing, China
• College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, China
• Department of Civil and Environmental Engineering, University of California, Irvine, CA, USA
• Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA
• College of Water Sciences, Beijing Normal University, Beijing, China
• CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra, Catalonia, Spain
• CREAF, Center for Ecological Research and Forestry Application, Cerdanyola del Vallès, Catalonia, Spain

Short Summary

This study reveals that flash droughts cause significantly greater global vegetation loss (9.0%) and delay recovery compared to conventional droughts (5.3%), with increasing frequency of flash droughts being the primary driver of this exacerbation.

Objective

• To comprehensively assess the global impact of flash and conventional droughts on vegetation dynamics (using Normalized Difference Vegetation Index (NDVI)-based metrics), focusing on post-drought NDVI recovery, by introducing an optimized methodology that accounts for lagged responses and offset effects.

Study Configuration

• Spatial Scale: Global land surface, with data regridded to a 0.5° × 0.5° latitude-longitude spatial resolution. Analysis also includes 28 regions with dominant vegetation types.
• Temporal Scale: 1982–2022 for drought and NDVI analysis; 1982–2020 for NDVI recovery time trends. Daily data aggregated to pentad (5-day) means.

Methodology and Data

• Models used: Smooth spline regression (for NDVI baseline), multiple linear regression analysis (for driving factors and contributions).
• Data sources:
  • ERA5-Land reanalysis dataset (daily soil moisture (0–100 cm), precipitation, evapotranspiration, snowmelt) at 0.25° × 0.25° resolution.
  • NOAA Climate Data Record (CDR) of Advanced Very High Resolution Radiometer (AVHRR) Surface Reflectance (NDVI) at 0.05° × 0.05° resolution.
  • Berkeley Earth land temperature dataset (daily global land temperature) at 1° × 1° resolution.
  • HadCRUT4 dataset (monthly precipitation and potential evapotranspiration) at 0.5° × 0.5° resolution.
  • European Space Agency (ESA) Climate Change Initiative (CCI) Land Cover dataset (global land cover maps) at 300-meter resolution.
  • MODIS burned area product (post-2000) and AVHRR-LTDR burned area product (pre-2000).

Main Results

• NDVI loss during flash droughts (9.0%) is approximately 1.5 times higher than during conventional droughts (5.3%).
• Global NDVI loss due to flash droughts shows a significant upward trend of 1.8% per decade (1982-2022), primarily driven by increasing flash drought frequency (81.2% contribution).
• Flash droughts are more frequent (0.37 events per year) and more intense (global average minimum soil moisture percentile of 5.6%) than conventional droughts (0.25 events per year, 11.9% minimum soil moisture percentile).
• The average global NDVI recovery time after flash droughts is 31 pentads, which is 3.2 pentads longer than after conventional droughts (27.8 pentads).
• NDVI recovery time has significantly increased by 0.4 pentads per year from 1982 to 2020 for both drought types, particularly in tropical rainforests and temperate forests.
• Flash droughts have a shorter drought tolerance period (1–2 pentads) compared to conventional droughts (3–4 pentads), leading to a sharper NDVI decline.
• The higher NDVI losses from flash droughts are mainly attributed to their higher frequency (41.8%) and rapid soil moisture decline rate (40.2%).

Contributions

• Introduces an improved methodology for quantifying drought-induced global vegetation loss by incorporating lagged response dynamics of vegetation and compensatory/offset effects between consecutive drought events, and by separating fire-induced declines.
• Provides a comprehensive global assessment comparing the ecological impacts of flash droughts versus conventional droughts on vegetation loss and recovery dynamics.
• Quantifies the increasing trend in global vegetation loss due to flash droughts and identifies increasing frequency as the dominant driver.
• Highlights the longer recovery times for vegetation after flash droughts and the increasing trend in recovery time, especially in vulnerable biomes.
• Establishes a 5% per pentad soil moisture decline rate as a meaningful ecological threshold for accelerated NDVI damage accumulation.

Funding

• National Natural Science Foundation of China (42301018, U24A20572)
• Catalan Government grants SGR 2021–1333 and AGAUR2023 CLIMA 00118

Citation

@article{Chai2025Flash,
  author = {Chai, Yuanfang and Miao, Chiyuan and AghaKouchak, Amir and Pokhrel, Yadu and Fu, Yongshuo H. and Li, Xiaoyan and Ji, Jiachen and Zhang, Qi and Peñuelas, Josep},
  title = {Flash droughts exacerbate global vegetation loss and delay recovery},
  journal = {Nature Communications},
  year = {2025},
  doi = {10.1038/s41467-025-67173-x},
  url = {https://doi.org/10.1038/s41467-025-67173-x}
}