Chu et al. (2025) Increasing ecological drought risks with warming climate over Northwestern China

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2025
• Date: 2025-10-13
• Authors: Jiangdong Chu, Yuhan Liu, Haijiang Wu, Xiaoling Su, Vijay P. Singh, Tianliang Jiang, Te Zhang, Jiping Niu
• DOI: 10.1007/s00704-025-05796-2

Research Groups

• Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, China
• College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling, China
• Yellow River Jiaozuo Bureau within Yellow River Henan Bureau, Yellow River Conservancy Commission, Jiaozuo, China
• Department of Biological and Agricultural Engineering, Texas A&M University, College Station, TX, USA
• Zachry Department of Civil and Environmental Engineering, Texas A&M University, College Station, TX, USA
• State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing, China
• Research Center on Flood and Drought Disaster Reduction, China Institute of Water Resources and Hydropower Research, Beijing, China
• Three Gorges Digital Intelligence Institute, China Three Gorges University, Yichang, China

Short Summary

This study characterizes ecological drought in Northwestern China using a novel standardized ecological water shortage index (SEWDI) under CMIP6 SSP2-4.5 and SSP5-8.5 scenarios, revealing a significant increase in ecological drought risk with warming climate, particularly in western and central regions.

Objective

• To characterize ecological drought over Northwestern China (NWC) using the standardized ecological water shortage index (SEWDI) and five CMIP6 Global Climate Models under SSP2-4.5 and SSP5-8.5 scenarios.
• To assess the risk of ecological drought in NWC based on vulnerability, exposure, and resilience indicators.

Study Configuration

• Spatial Scale: Northwestern China (NWC), located at 34°00'−49°10'N and 73°15'−112°58'E, covering approximately 3.2 million km².
• Temporal Scale:
  • Historical (baseline) period: 1982–2014
  • Future periods: Near future (2026–2050), Middle future (2051–2075), Far future (2076–2100)
  • Total simulation period: 1982–2100

Methodology and Data

• Models used:
  • Coupled Model Intercomparison Project Phase 6 (CMIP6) Global Climate Models (GCMs): ACCESS-ESM1-5, BCC-CSM2-MR, FIO-ESM-2-0, GFDL-ESM4, MPI-ESM1-2-HR.
  • Shared Socioeconomic Pathways (SSPs): SSP2-4.5 (modest radiative forcing), SSP5-8.5 (high radiative forcing).
  • Bias-Corrected Spatially Disaggregated (BCSD) technique for GCM output downscaling.
  • Standardized Ecological Water Deficit Index (SEWDI) based on Ecological Water Deficit (EWD).
  • Run theory with three thresholds (0, -0.3, and -0.5) for drought characteristic extraction.
  • Rotation Empirical Orthogonal Function (REOF) for spatial division of ecological drought.
  • Weighted additive model for ecological drought risk calculation.
• Data sources:
  • Reanalysis: ERA5 (monthly 10 m wind speed, net radiation; 0.25°×0.25° spatial resolution).
  • Observation/Gridded: CN05.1 (daily precipitation, air temperature, relative humidity; 0.25°×0.25° spatial resolution).
  • Land Surface Model: GLDAS Noah (0-10 cm soil moisture; 0.25°×0.25° spatial resolution).
  • Satellite: GLOBMAP (semi-monthly Leaf Area Index (LAI); 8 km×8 km spatial resolution), GIMMS NDVI3g (semi-monthly Normalized Difference Vegetation Index (NDVI); 1/12°×1/12° spatial resolution).
  • Ancillary/Derived: Resources and Environmental Science and Data Center (soil texture grain map of China), National Oceanic and Atmospheric Administration (NOAA) (CO2 concentration), Land-Use Harmonization 2 (LUH2) project (annual land-use layers; 0.25°×0.25° spatial resolution).
  • All datasets were bilinearly interpolated to a consistent 0.25° spatial resolution.

Main Results

• The Standardized Ecological Water Deficit Index (SEWDI) effectively characterizes ecological drought and vegetation dynamics in Northwestern China (NWC).
• Mean, maximum, and minimum temperatures are projected to increase across NWC under both SSP2-4.5 and SSP5-8.5 scenarios. By the end of the 21st century, mean temperature is projected to increase by 2.4 °C under SSP2-4.5 and 5.8 °C under SSP5-8.5.
• Precipitation shows an increasing trend but with higher variability. CO2 concentration and reference evapotranspiration (ET0) are also projected to increase, with ET0 anomaly increments of 81 mm (SSP2-4.5) and 107 mm (SSP5-8.5) by the end of the 21st century.
• Ecological drought is projected to intensify across most of NWC under both scenarios, with more severe droughts under SSP5-8.5, especially in the middle and far future.
• The decrement rate of ecological drought severity is projected to exceed –0.022 per decade over NWC in the middle future (2051-2075) under both scenarios.
• Ecological drought frequency, duration, and severity are projected to increase in a warmer climate. Longer durations (>12 months) and larger severities (>12) are particularly projected in the western and southern parts of NWC in the middle and far futures.
• Regions with higher ecological drought risk (larger vulnerability, stronger exposure, weaker resilience) are mainly located in the western and central parts of NWC, while lower risk is in the eastern parts.
• The projected ecological drought risk over NWC is significantly increased compared to the historical period (1982-2014) under both SSP2-4.5 and SSP5-8.5 scenarios. Mean relative risk changes for NWC range from 55% to 162% across future periods and scenarios, indicating a potential tripling of ecological drought risk.

Contributions

• Proposed and validated a novel index, SEWDI, for ecological drought monitoring that effectively captures vegetation water stress by integrating ecological water deficit dynamics, addressing limitations of traditional vegetation-based indices.
• Provided a comprehensive risk assessment of ecological drought over Northwestern China under future warming scenarios (SSP2-4.5 and SSP5-8.5), combining vulnerability, exposure, and resilience indicators at a regional scale, which was previously lacking.
• Quantified the spatiotemporal evolutions and risk changes of ecological drought, including frequency, duration, and severity, offering critical insights for region-specific adaptation measures and sustainable water and ecosystem management in arid regions.

Funding

• National Natural Science Foundation of China (Grant No. 52079111, 52479027, and 51879222)
• Key Science and Technology Project of the Ministry of Water Resources (Grant No. SKS-2022018)

Citation

@article{Chu2025Increasing,
  author = {Chu, Jiangdong and Liu, Yuhan and Wu, Haijiang and Su, Xiaoling and Singh, Vijay P. and Jiang, Tianliang and Zhang, Te and Niu, Jiping},
  title = {Increasing ecological drought risks with warming climate over Northwestern China},
  journal = {Theoretical and Applied Climatology},
  year = {2025},
  doi = {10.1007/s00704-025-05796-2},
  url = {https://doi.org/10.1007/s00704-025-05796-2}
}