Invasive Species Alter Western Ghats Hydrology and Soil Structure

Invasive alien species are influencing vegetation expansion in India's Western Ghats, potentially altering local hydrological cycles and soil biogeochemistry in ways that affect regions hundreds of kilometres away, according to ecologist Jagdish Krishnaswamy of the Indian Institute for Human Settlements. Krishnaswamy presented findings from satellite-based Greening and Browning Atlases at the Anil Agarwal Dialogue 2026 in Rajasthan.

The Greening and Browning Atlas of India, which maps vegetation density changes from 1982-2022 and 2000-2022, shows that while some regions have gained green cover, that growth may partly reflect the spread of invasive alien species rather than native forest recovery. In the Western Ghats, such shifts could disrupt biogeochemical soil structure. Krishnaswamy noted that forests in the Western Ghats release moisture through evapotranspiration that travels eastward with prevailing winds, reaching water-scarce eastern coastal regions — meaning Western Ghats degradation can affect water availability far beyond the forest boundary.

The atlas also reveals simultaneous drying in several regions alongside unusual increases in wetness in others. Increased rainfall has been recorded in parts of Rajasthan's northwest, linked in part to the Indira Gandhi Canal, while other areas show intensifying drought. Krishnaswamy presented India's Surface Water Trends dataset alongside the Wetting and Drying Atlas, showing temporal changes in lakes, ponds and water bodies. He emphasised that the water crisis is not simply one of scarcity but of imbalance — excessive rainfall and flooding occurring alongside prolonged drought in different parts of the same country.

Krishnaswamy, a former Coordinating Lead Author for the IPCC Special Report on Climate Change and Land, called for recognition that ecological changes in India are outcomes of interconnected systems, not isolated events. He cautioned that riverfront development may not be ecologically appropriate for urban rivers, and that river sediment reaching the sea is vital for estuarine and coastal ecosystem stability. He also distinguished between blue water (freshwater in rivers, lakes, and aquifers) and green water (rainwater stored in soil used by vegetation), arguing that green water requires far more careful management amid growing climate variability.

Key figure — Greening and Browning Atlas tracks vegetation changes from 1982-2022