Deforestation causing weaker monsoons in India, finds study

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25 August 2016

Deforestation and conversion of forest land to crop land has weakened the monsoon in India, a study by a team from the Indian Institute of Technology (IIT)-Bombay has found.

The team from the Interdisciplinary Program in Climate Studies of IIT-B studied recent changes of land use and found that rainfall received in north-eastern and north-central India has reduced owing to the destruction of forests.

''Due to the large-scale deforestation, there has been a significant drop in the amount of rainfall received,'' said Subimal Ghosh, a faculty member associated with the study.

''Forests are deep-rooted and have more leaf area index (an indicator of plant canopies). They facilitate more recycled precipitation, a source of rainfall,'' he said.

Ghosh said the conversion of forests to crop land, particularly in north-eastern and north-central India, has reduced the amount of rainfall received in these areas.

''In these areas, recycled precipitation is a major source of rainfall, contributing 20-25 per cent of the total rainfall during the end of monsoon,'' said Ghosh.

However, the team which studied data for two decades (1980-90 and 2000-2010), found that the recycled precipitation had reduced at places where forest land had been converted to agricultural land.

''Large-scale conversion of forest land to crop land resulted in conversion of deep-rooted vegetation to shallow-rooted vegetation. Forests also have higher leaf area index than crops,'' said Ghosh.

Ghosh said the findings of the study should be considered while designing climate change mitigation policies.

The study, published in Nature Publishing Group's Scientific Reports, was conducted by three students and two faculty members in association with the Nebraska Lincoln University, USA.

''We studied the satellite data of two decades on the land use pattern. While we worked on simulation models, the satellite data shows visible evidence of decrease in green cover,'' said Ghosh.

''If deforestation continues at the current rate, the Indian subcontinent could dry up due to warming of the Western Indian Ocean, as suggested by other studies too,'' said Ghosh.





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