Kashyap et al. (2025) Ecological droughts increased in India with changing Indian summer monsoon and human interventions

Identification

• Journal: Communications Earth & Environment
• Year: 2025
• Date: 2025-10-28
• Authors: Rahul Kashyap, J. Kuttippurath, Vikas Patel
• DOI: 10.1038/s43247-025-02694-3

Research Groups

• CORAL, Indian Institute of Technology Kharagpur, Kharagpur, India

Short Summary

This study investigates ecological droughts, their drivers, and implications in India during the Indian Summer Monsoon (2000–2019) using remote sensing and machine learning. It finds that ecological droughts are increasing in ecologically fragile pristine forests and croplands, primarily driven by meteorological aridity (23.9%) and ocean warming (18.2%), leading to declining vegetation health.

Objective

• To identify regions vulnerable to ecological droughts in India.
• To determine the relationship between various forms of aridity (meteorological, land evaporative, and atmospheric) and ecological droughts in India.
• To assess how ocean warming and climate oscillations impact vegetation health in India.
• To investigate how human-ecosystem interactions influence vegetation health in India.
• To provide implications and recommendations to combat ecological droughts in India.

Study Configuration

• Spatial Scale: Pan-India, with detailed analysis for various bioclimatic regions: Hilly Region (HR), Northeast (NE), Indo-Gangetic Plain (IGP), Northwest (NW), Central India (CI), and Southern India (SI).
• Temporal Scale: Indian Summer Monsoon (June-September, JJAS) season during the period 2000–2019, including decadal changes (2000–2009 vs. 2010–2019).

Methodology and Data

• Models used: Random Forest (RF), Multiple Linear Regression (MLR), Rotated Principal Component Analysis (RPCA), Peter and Clarke’s Momentary Conditional Independence (PCMCI) / PCMI+ (causal discovery).
• Data sources:
  • Remote Sensing: MODIS Land Use and Land Cover (LULC), Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), Sea Surface Temperature (SST).
  • Reanalysis: Global Precipitation Measurement (GPM) precipitation, Global Land Data Assimilation System (GLDAS) soil moisture and air temperature, TerraClimate Actual Evapotranspiration (AET), Potential Evapotranspiration (PET), Palmer Drought Severity Index (PDSI), Vapour Pressure Deficit (VPD).
  • Indices/Observations: Human Modification Index (HMI), Forest Landscape Integrity Index (FLII), WorldPop (population count), Oceanic Niño Index (ONI), Indian Ocean Dipole (IOD) index (Dipole Meridional Index, DMI), Pacific Meridional Mode (PMM), North Atlantic Oscillation (NAO).

Main Results

• Ecological droughts are increasing in ecologically sensitive regions of India, including the Himalaya, Northeast, eastern Indo-Gangetic Plain, Central India, and southern South India.
• Meteorological aridity (PDSI) is the dominant driver of ecological droughts (23.9% contribution), followed by ocean warming (SST) (18.2%). Land evaporative aridity (ETR) (14%) and atmospheric aridity (VPD) (12.4%) also contribute significantly.
• Causal analysis reveals that ocean warming indirectly triggers ecological droughts by influencing moisture availability, thermal conditions, and atmospheric aridity.
• Human interventions, such as population growth, land use changes, and forest fragmentation, contribute to forest degradation and increased ecological droughts.
• A potential westward shift of the Indian Summer Monsoon system is linked to increased ecological droughts in eastern and southern India.
• The rising ecological droughts, driven by enhanced aridity, ocean warming, and human interventions, are causing browning in intensive croplands of eastern Indo-Gangetic Plain, southern South India, and forests in the Himalaya, Northeast, and Central India.

Contributions

• This study provides the first comprehensive analysis of ecological droughts, their drivers, mechanisms, and implications for India.
• It expands the understanding of droughts by explicitly addressing their ecological impacts, which are often overlooked in conventional drought definitions.
• The research unveils complex non-linear interactions among atmosphere-land-ocean (ALO) systems in driving ecological droughts in India.
• The findings offer a better understanding of ecological water demand and the repercussions of droughts, applicable to India and other regions with similar ecohydrology.

Funding

• PMRF (Prime Minister's Research Fellowship) from the Ministry of Education (MoE) for Rahul Kashyap.
• Ministry of Education (MoE) and Indian Institute of Technology Kharagpur (IIT KGP) for Vikas Kumar Patel.

Citation

@article{Kashyap2025Ecological,
  author = {Kashyap, Rahul and Kuttippurath, J. and Patel, Vikas},
  title = {Ecological droughts increased in India with changing Indian summer monsoon and human interventions},
  journal = {Communications Earth & Environment},
  year = {2025},
  doi = {10.1038/s43247-025-02694-3},
  url = {https://doi.org/10.1038/s43247-025-02694-3}
}