Aravallis lost 13.8% soil per year during 2017-2024: Study

New Delhi: Built-up areas in India's Aravallis have increased 53 per cent, resulting in a 13.8 per cent increase in average soil lost per year during 2017-2024, even as forest cover has increased in the country's oldest mountain range over the time period, a study has found.

Assessing land use and land cover patterns between 2001 and 2021, researchers from O.P. Jindal Global University and the Indian Institute of Technology Kharagpur found that steep slopes, susceptible soils and mining areas are strongly associated with erosion hotspots.

An increased soil erosion in the Aravalli Mountain System, despite a significant increase in afforestation, highlights that local conservation efforts cannot compensate for massive land conversion, according to findings published in the journal Geographies.

The Aravallis are primitive mountains where soils are deep and ecosystems intricate and delicately balanced, the researchers said.

The range is among India's most-mineral rich mountain systems, hosting a wide range of metallic and non-metallic minerals and serving as a cornerstone of India's mineral resource base.

The team analysed moderate-resolution data recorded during 2001-2020 to identify long-term trends, with high-resolution data of 2017 and 2024 selected to accurately measure erosion trends. The two years represent current and divergent meteorological conditions, they said.

The study revealed "an evident growth in overall forest cover at a broad spatial scale".

However, fine-scale measurement showed erosive processes and a sharp growth in built environments and a subsequent depopulation of rangelands and croplands.

The trend is similar to that seen in ancient mountain systems worldwide, the researchers said.

"LULC (land use and land cover) has changed rapidly, with built-up areas increasing by 53 per cent at the expense of rangelands and croplands. These drivers resulted in a 13.8 per cent increase in the mean annual soil loss between 2017 and 2024, from 1.59 to 1.81 t/ha/yr (tonnes per hectare per year), while forest cover has increased over the timescale, as is evident in this study," the authors wrote.

Conversion of semi-natural vegetation surfaces to built, impervious surfaces has a direct, negative effect on the land's natural defence mechanisms, they said.

The team added that a lack of forest does not afflict landscapes, but through the disintegration and transformation of the larger, stabilizing land matrix, ecosystems downstream are affected.

Human-caused erosion of the landscape was found to be accompanied by an increase in climatic erosivity between 2017 and 2024.

The interdependence of human activity and climate change, in which human activity increases exposure and climate change increases hazards, is characteristic of the contemporary degradation of vulnerable ecosystems across the globe, the authors said.

"As a result, a 13.83 per cent increase in mean soil erosion rates became a direct and foreseeable effect," they said.

"These results highlight the fact that local conservation benefits, such as afforestation, can be swamped out by large, unsustainable land conversion processes," the team wrote.