Large scale conversion of forest land weakening monsoon: Study

Monsoon has weakened in the North-Eastern and North-Central India due to large-scale conversion of forest land to crop land, according to a study by the Indian Institute of Technology (IIT) Bombay.
The study undertaken by the IIT's Interdisciplinary Programme in Climate Studies warned that the condition would become "more critical" if deforestation continues at the present rate.
"Changes and variability of Indian monsoon are traditionally linked to large-scale atmospheric and oceanic circulations. Their association with local factors, such as, the recent changes of land use land cover (LULC) are largely overlooked," an official statement said.
Satellite data revealed large-scale changes of LULC in India, specifically in terms of the conversion of forest land to crop land.

Large-scale deforestation has been observed in India when the LULC map derived from Moderate Resolution Imaging Spectro-Radiometer (MODIS) for 2000s is compared with that derived from Advanced Very High Resolution Radiometer (AVHRR) for 1980s.
The changes are visible in terms of significant decrease in the leaf area index, a term used to measure the green cover, it said.

A regional simulation of Indian south-west monsoon with two different LULC of 1980s and 2000s, keeping all the large-scale circulation same, reveals statistically significant reduction in monsoon rainfall over North-Central and North Eastern India with the changes in forest cover.
Large-scale conversion of forest land to crop land resulted in conversion of deep-rooted vegetation to shallow-rooted vegetation that further reduces evapo-transpiration (ET), a local moisture source to precipitation, it said.

"The precipitation that is being generated from local evapo-transpiration is known as recycled precipitation," it added.
Work on the impact of large-scale LULC has significant implication in terms of generating rainfall projections for future to be used for climate change adaptation. Climate models are mostly forced with increasing Green House Gas emissions, largely ignoring the future possible changes in LULC.
Recent studies show drying of Indian sub-continent due to warming of Western Indian Ocean. This condition would become more critical if deforestation continues at the present rate, the study noted.
"This needs to be seriously considered in the development of national policy of regional climate change mitigation," it said.