29 April 2024

In India, 30 percent of the soil is at risk of erosion


A study illustrates for the first time the extent of the phenomenon in India. For 3 percent of the area, the situation is defined as “catastrophic” according to the new classification

by Matteo Cavallito


Over twenty tons of soil per hectare per year: this is the extent of erosion experienced by India. In total, the phenomenon affects almost 30 percent of the total area in a mild form. Three percent, however, would be affected by “catastrophic” soil loss. This was revealed in a study by the Indian Institute of Technology Delhi, the first of its kind to provide an overall nationwide estimate.

The study represents a novelty, explained Manabendra Saharia, a professor and co-author of the research surveyed by the DownToEarth portal. “We wanted to have a holistic view of soil erosion in the country.”

The first national estimate of erosion

Typically, the authors write, erosion “removes the topmost fertile layer of soil, affecting agricultural productivity on a larger scale.” This is particularly problematic for India, whose economy still depends for a significant share on agriculture. Yet, the study notes, “a national-scale assessment of soil erosion and an impact classification system currently doesn’t exist over India.”

To fill this gap and to avoid at the same time resorting to a field analysis that would have been too time-consuming and costly, the researchers thus relied on a system known as RUSLE or Revised Universal Soil Loss Equation.

The equation takes into account several factors such as expected crop loss, rainfall and runoff, soil erosion propensity, steepness and length of a mountain slope, crop management and support practices, acting with a spatial resolution of 250 meters. Its application thus led to the estimation of potential annual soil loss across India by quantifying its variability. Precipitation would prove to have the greatest influence among all factors considered.

India loses an average of 21 tons of soil per hectare per year

The study came up with six classifications placed on a scale ranging from “minor” to “catastrophic” in terms of soil eroded on one hectare in a year. When the figure exceeds 100 tons, the phenomenon reaches the most severe level.

The worst situation is in the Brahmaputra Valley located in the northeastern state of Assam. Here the erosion phenomenon affects nearly 300 square kilometers of surface soil, accounting for 31 percent of the total.

Also according to the study, quoted by DownToEarth, nine of the 20 districts most susceptible to soil erosion in the country are located in Assam. In India, the national average erosion is estimated at 21 tons per hectare per year. This loss can be directly attributed to anthropogenic interventions such as deforestation and intensive agricultural practices.

L'andamento dell'erosione dei suoli nei diversi continenti. FONTE: FAO, 2019.

Soil erosion trends on different continents. SOURCE: FAO, 2019.

3 percent of the soil is subject to “catastrophic” erosion

Nationwide, the study continues, catastrophic erosion affects 3.2 percent of the total land area. This is a worrisome finding that parallels other previous findings. Past studies, the authors recall, have revealed that 68 percent of the total eroded land in India is owed its condition to the action of water. In addition, 29 percent of this eroded soil is transported to the sea and is permanently lost.

Finally, erosion causes 74 million tons of nutrients to be lost from the soil surface each year with economic damage to Indian agriculture estimated at about 68 billion rupees per year (over $800 million at current exchange rates). Adoption of the classification system introduced by the study, the researchers conclude, will enable the planning and implementation of soil conservation strategies at both local and national levels.