Only one of four river basins in India can support vegetation during a drought year: Study
The findings assume importance since previous studies have reported an increase in the intensity and frequency of droughts in Indiamumbai Updated: Oct 02, 2017 12:05 IST
Only one out of four river basins in India can support vegetation during a drought year, posing a threat to the country’s agricultural productivity and food security, a first-of-its-kind study has revealed.
A two-member team from the Indian Institute of Technology — Guwahati (IIT-G) prepared an ecosystem resilience map of India from 2000 to 2014 to find that only six of the 22 river basins can support crop yield and vegetation during a drought. This means as much as two-third of the country’s vegetation — including crop land, forests, grasslands and shrub lands — is not resilient.
A resilient ecosystem can absorb hydro-climatic disturbances, such as a drought, by increasing or maintaining its efficiency to use water to help sustain its productivity.
The findings assume importance since previous studies have reported an increase in the intensity and frequency of droughts in India. A 2015 study found that droughts have shifted towards the Indo-Gangetic area, central Maharashtra and coastal south-India plains that are important for agriculture.
Of all the land-based vegetation, crop lands cover about 50% of the total geographical area, and are therefore the most dominant in India. Geographically, Uttar Pradesh (UP), Madhya Pradesh (MP), Rajasthan, Gujarat, and parts of Maharashtra, Andhra Pradesh (AP) and Odisha are most vulnerable to drought.
“In the context of climate change, droughts have become recurring events. With a population of 1.2 billion that needs to be fed, it is important to know which ecosystem is resilient. If the vegetation around the river basin is not resilient, crop production will get severely affected,” said lead investigator Manish Kumar Goyal, also assistant professor, department of civil engineering, IITG.
“A national water policy does not serve any purpose as some areas have surplus water and others are water deficient. There is a need to have a local strategy, as opposed to a regional or national policy, to address these challenges. Developing local water management practises and drought-resilient crops could be among the solutions,” he added.
The Ganga basin — the largest in terms of its geographical area and most the populous since it runs through 11 states — was found to be non-resilient along with basins along the Western Ghats, and India’s central and eastern regions. The Mahi river basin that covers Rajasthan, Gujarat and MP — is the most non-resilient.
“One-third of the population lives in the Ganga river basin, and a non-resilient ecosystem will not be able to withstand droughts, which are expected to increase multifold in terms of intensity, severity and frequency,” said Goyal. “Concrete steps need to be taken in terms of formulating and implementing policies at local level,” he added.
Despite the high annual rainfall and water surplus, river basins along the Western Ghats are unable to maintain their efficiency to use water during a drought year.
Of the seven land cover types studied, as many as five — cropland, a mix of cropland and natural vegetation, grasslands, mixed forest and deciduous broadleaf forest — are not resilient. Only evergreen needle leaf and evergreen broadleaf forests can withstand a drought.
The Indus river basin was the most resilient, followed by Brahmaputra, three basins along coastal south India and one located in arid and semi-arid drought-affected regions of Rajasthan and Gujarat.
With 60% forest cover, the Brahmaputra basin that runs through Arunachal Pradesh, Assam, Meghalaya, Nagaland, West Bengal and Sikkim is highly resilient.
“Forest cover is the most important parameter for ecosystem resilience, and the Brahmaputra basin and Western Ghats can withstand the challenges of climate change that will affect agriculture and water security in the other basins,” said Goyal. “Development needs deforestation, but there should not be continuous deforestation. It should be minimal and within the purview of the ecosystem, so there is no adverse effect on crop production,” he said.
On the other hand, ecosystems in arid regions are habituated to the limited water conditions owing to frequent droughts and are hence resilient. The study is published in Global Change Biology, a high impact factor Wiley journal.