New Delhi

Annual gross primary productivity over India, or the rate at which plants, algae and other producers convert solar energy into chemical energy via photosynthesis, increased during the three decades ending 2014, according to a study.

It projected a continued enhancement of the productivity until 2100 even under a high-emissions scenario.

Stronger precipitation increases together with coupled carbon dioxide fertilisation effects of plants in response to elevated levels of CO2 in the air could be a reason for the enhanced plant productivity projected trends, researchers, including those from the Indian Institute of Tropical Meteorology in Pune, said in the study, published in the International Journal of Climatology.

They added that the future productivity trends could be up to 2.5 times the historical ones, with the largest increases projected to occur over the Indo-Gangetic Plain, Northeastern India and the Western Ghats.

The modelled trends were found to be broadly in line with observed increases in forest and crop cover.

The team looked at historical (1985-2014) and future (2015-2100) changes in gross primary productivity over India using Earth system models from CMIP6 -- they provide scientific data for Intergovernmental Panel on Climate Change (IPCC) reports.

The researchers also compared the assessment of gross primary productivity by CMIP5 and CMIP6 simulations under high-emission scenarios.

"Results indicate a robust increase in annual GPP over India during the historical period, with continued enhancement under the SSP5-8.5 scenario," the authors wrote.

"CMIP6 projects substantially stronger future GPP increases than CMIP5, with future GPP (gross primary productivity) trends up to (nearly) 2.5 times the historical trend magnitude over the country. Spatially, the largest increases occur over the Indo-Gangetic Plain, Northeastern India and the Western Ghats region," they said.

The analysis further suggests that years with a higher rainfall generally enhance productivity, while years with higher temperatures suppress productivity through heat and moisture stress.

"Overall, the study demonstrates that long-term greening over India appears to be associated with combined CO2 fertilisation and enhanced precipitation trends," the authors said.

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The findings highlight the importance of accurately representing hydro-climatic processes and biosphere-atmosphere interactions for projecting future terrestrial productivity over monsoon-dominated regions, they said.