Wang et al. (2025) Unequal impacts of future droughts on global croplands: contributions of climate and land-use changes across different income groups

Identification

• Journal: npj natural hazards.
• Year: 2025
• Date: 2025-10-08
• Authors: Xu‐Sheng Wang, Ye Xu, Wei Li, Yurui Fan
• DOI: 10.1038/s44304-025-00144-w

Research Groups

• MOE Key Laboratory of Regional Energy and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing, China
• Department of Civil and Environmental Engineering, Brunel University of London, Middlesex, UK

Short Summary

This study globally assesses future cropland exposure to drought risks under climate change, considering both climate variability and land-use changes across income groups. It finds substantial increases in extreme drought risks, particularly for lower-middle-income countries, with climate change emerging as the dominant driver.

Objective

• To present a global assessment of future cropland exposure to drought risks under climate change, accounting for both climate variability and land-use changes across different income groups.
• To quantify the concurrence risks of 3-month and 6-month droughts and assess the transitional risks of 3-month droughts evolving into 6-month droughts using SPI and SPEI.
• To quantify the extent of croplands in countries with different income levels threatened by concurrent and transitional droughts.
• To evaluate the relative contributions of climate change, land-use dynamics, and their interactions to future cropland exposure.

Study Configuration

• Spatial Scale: Global, with GCM outputs regridded to 250 km resolution. Cropland data at 1 km resolution, aggregated to GCM grid cells. Analysis across six continents and four income groups (High-Income, Upper-Middle-Income, Lower-Middle-Income, Low-Income countries based on World Bank 2022 classification).
• Temporal Scale: Historical period (1951–2010) and Future period (2041–2100). Droughts assessed for 3-month (April–June in Northern Hemisphere, October–December in Southern Hemisphere) and 6-month (April–September in Northern Hemisphere, October–March in Southern Hemisphere) periods.

Methodology and Data

• Models used:
  • Standardized Precipitation Index (SPI)
  • Standardized Precipitation Evapotranspiration Index (SPEI)
  • Copula-based method (Gaussian, Gumbel, Frank, and Joe copulas selected based on Akaike Information Criterion (AIC) and Kolmogorov-Smirnov (K-S) goodness-of-fit tests) for quantifying joint and transitional drought risks.
  • 12 CMIP6 Global Climate Models (GCMs): ACCESS-CM2, ACCESS-ESM1-5, CMCC-CM2-SR5, EC-Earth3, GFDL-ESM4, INM-CM4-8, INM-CM5-0, IPSL-CM6A-LR, MIROC6, MPI-ESM1-2-HR, MPI-ESM1-2-LR, MRI-ESM2-0.
  • Shared Socioeconomic Pathways (SSPs): SSP245 (intermediate emissions) and SSP585 (high emissions).
  • Decomposition approach (Equations 6, 7a-7c) for attributing contributions of climate change, cropland change, and their interaction.
• Data sources:
  • CMIP6 climate projections (monthly precipitation and potential evapotranspiration (PET)) from the World Climate Research Programme (WCRP) and Bjarke et al. (2023) for PET (Penman–Monteith method).
  • Global cropland proportion dataset (1 km resolution) from Cao et al. (2021).

Main Results

• Drought Concurrence Risks: SPI-based severe drought concurrence shows modest increases (mostly within ±1 percentage point), while extreme drought concurrence increases significantly (up to 10 percentage points in some regions under SSP585). SPEI-based severe drought concurrence shows slight increases (within 5 percentage points), but extreme drought concurrence shows substantial increases (up to 20 percentage points under SSP245, over 60 percentage points under SSP585 in hotspots like northwestern China, Europe, northern/southern Africa).
• Drought Transition Risks: Both SPI and SPEI indicate rising probabilities of 3-month droughts evolving into 6-month extreme droughts. SPEI-based results show significantly higher increases (exceeding 50 percentage points in central/western Eurasia, northern Africa, North/South America, southwestern Australia), highlighting the amplifying effect of temperature-driven evapotranspiration.
• Cropland Exposure: SPI-based extreme drought concurrence exposure doubles under SSP245 and quadruples under SSP585 globally, with lower-middle-income (LMI) countries facing the highest increase (>350%). SPEI-based extreme drought concurrence exposure surges by 2000% under SSP245 and over 4200% under SSP585 globally, with LMI countries experiencing the highest rise (~5000%). SPEI-based transitional drought exposure increases by ~250% under SSP245 and ~350% under SSP585 globally.
• Contributions of Drivers: Climate change is the dominant driver of increased cropland exposure to both concurrent and transitional drought risks, with its influence strengthening under SSP585 (often exceeding 100% contribution). The role of land-use change diminishes under high-emission scenarios, often becoming negligible or even negative. High-income countries are overwhelmingly climate-driven, while low-income and LMI countries shift from mixed climate-cropland influences under SSP245 to near-total climate dependence under SSP585.

Contributions

• Provides the first global assessment that integrates multi-timescale drought analysis (3- and 6-month SPI/SPEI) with a copula-based approach to quantify both concurrent and transitional drought risks.
• Systematically quantifies global cropland exposure to compound drought transitions, offering a more dynamic and integrative perspective on agricultural drought risk.
• Analyzes how cropland expansion and associated drought exposure risks differ across income levels under varying climate change scenarios (SSP245, SSP585).
• Evaluates the relative contributions of climate change, land-use dynamics, and their interactions to future cropland exposure, identifying climate change as the primary driver, especially under high-emission scenarios.
• Highlights the amplifying impact of temperature-driven evapotranspiration on drought persistence and severity, particularly for SPEI-based extreme and transitional droughts.
• Underscores the unequal impacts of climate change on global agriculture, with lower-middle-income countries facing disproportionately higher risks.

Funding

• National Natural Science Foundation of China (Grant No. 62073134)

Citation

@article{Wang2025Unequal,
  author = {Wang, Xu‐Sheng and Xu, Ye and Li, Wei and Fan, Yurui},
  title = {Unequal impacts of future droughts on global croplands: contributions of climate and land-use changes across different income groups},
  journal = {npj natural hazards.},
  year = {2025},
  doi = {10.1038/s44304-025-00144-w},
  url = {https://doi.org/10.1038/s44304-025-00144-w}
}