You et al. (2025) Decadal trends in global grassland growth peaks and their drivers since the 1980s

Identification

• Journal: Nature Communications
• Year: 2025
• Date: 2025-10-28
• Authors: Cuihai You, Shiping Chen, Zhiqin Tu, Chenyu Bian, Erqian Cui, Kun Huang, Fayu Wan, Jiaye Ping, Ning Wei, Jianyang Xia
• DOI: 10.1038/s41467-025-64565-x

Research Groups

• Research Center for Global Change and Ecological Forecasting, School of Ecological and Environmental Sciences, Institute of Eco-Chongming, East China Normal University, Shanghai, China
• Institute of Botany, Chinese Academy of Sciences, Beijing, China
• School of Integrative Plant Science, College of Agriculture and Life Sciences, Cornell University, Ithaca, NY, USA

Short Summary

This study reveals a widespread increase in global grassland growth peaks from 1982 to 2021, but identifies a significant reversal between 1998 and 2009 across 64% of regions, primarily driven by a global-scale decadal drought.

Objective

• To investigate the long-term trends in global grassland growth peaks since the 1980s and identify the drivers of any observed changes or interruptions, particularly whether increasing drought intensity threatens their ecological functions.

Study Configuration

• Spatial Scale: Global grasslands, analyzed across 28 IPCC climate regions at an aggregated resolution of 0.1° × 0.1°.
• Temporal Scale: 1982 to 2021 for overall trends, with a focus on the 1998 to 2009 period for observed interruptions.

Methodology and Data

• Models used:
  • Breaks For Additive Season and Trend (BFAST) method for detecting abrupt changes.
  • Machine learning (XGBoost, Random Forest) for upscaling eddy covariance flux measurements to generate a global Gross Primary Productivity (GPP) dataset and for factorial experiments to quantify environmental contributions.
  • EC-LUE model for an independent GPP dataset.
• Data sources:
  • Satellite-derived vegetation data: GIMMS-4g Normalized Difference Vegetation Index (NDVI) (1982–2021), MODIS Enhanced Vegetation Index (EVI) (2001–2021), Solar-induced Chlorophyll Fluorescence (CSIF) (2001–2018).
  • Observation/Reanalysis data: Eddy covariance flux measurements from 75 grassland sites (1982–2020), ECMWF ERA5 reanalysis for solar radiation, precipitation, and air temperature (1982–2021), NOAA Global Monitoring Laboratory for CO2 concentration, TRENDY model for nitrogen deposition rate, Land-Use Harmonization (LUH2) dataset for cropland and rangeland fractions, MODIS Land Cover Climate Modeling Grid (MCD12C1) for grassland areas, IPCC Atlas of Global and Regional Climate Projections for regional classification, and SPEI-12 for drought quantification.

Main Results

• Global grassland NDVImax significantly increased at a rate of 0.55 ± 0.08 × 10⁻³ yr⁻¹ from 1982 to 2021, with 68% of grassland areas showing an upward trend.
• A significant reversal occurred between 1998 and 2009, with global NDVImax declining at −0.69 ± 0.40 × 10⁻³ yr⁻¹ and GPPmax declining at −6.27 ± 0.31 × 10⁻³ g C m⁻² d⁻¹ yr⁻¹.
• During the 1998–2009 period, 64% (18 out of 28) of IPCC climate regions exhibited decreasing NDVImax trends, and 54% (15 out of 28) showed decreasing GPPmax trends.
• The Tibetan Plateau and East Asia were identified as primary contributors to the global downturn in grassland growth peaks during 1998–2009.
• The interruption was primarily driven by a decadal drought, characterized by a sharp decline in precipitation at a rate of −5.34 ± 1.4 mm yr⁻¹, which was four times faster than the rate over the entire 1982–2021 period.
• Factorial experiments confirmed that climate change, particularly reduced precipitation, was the dominant driver of the decline, outweighing positive effects from rising CO2, nitrogen deposition, and land-use changes.

Contributions

• Reveals a critical, previously overlooked decade-long stagnation (1998–2009) in global grassland growth peaks, interrupting a general upward trend observed since 1982.
• Quantifies the widespread nature of this reversal across 64% of IPCC climate regions, with significant impacts in key areas like the Tibetan Plateau and East Asia.
• Identifies a global-scale decadal drought, characterized by sharp precipitation declines, as the primary driver of this interruption, highlighting the high vulnerability of grasslands to climate variability.
• Provides a robust, globally continuous GPP dataset (1980–2020) generated by upscaling eddy covariance flux measurements using machine learning, which independently validates satellite-derived vegetation patterns.
• Emphasizes that persistent drought poses a spatially uneven but widespread threat to the ecological functions of grasslands under climate change, challenging the prevailing global greening narrative.

Funding

• National Natural Science Foundation of China (32325033, 32401389, U22A20559)
• National Key R&D Program of China (2022YFF0802104; 2023YFF1305301)
• Shanghai Pilot Program for Basic Research (TQ20220102)

Citation

@article{You2025Decadal,
  author = {You, Cuihai and Chen, Shiping and Tu, Zhiqin and Bian, Chenyu and Cui, Erqian and Huang, Kun and Wan, Fayu and Ping, Jiaye and Wei, Ning and Xia, Jianyang},
  title = {Decadal trends in global grassland growth peaks and their drivers since the 1980s},
  journal = {Nature Communications},
  year = {2025},
  doi = {10.1038/s41467-025-64565-x},
  url = {https://doi.org/10.1038/s41467-025-64565-x}
}