India’s forests are losing their ability to absorb carbon dioxide with their photosynthetic efficiency declining by up to 12 per cent in some dense forest areas over the past two decades, a new study has found.
The study is the first attempt to measure reduced photosynthetic efficiency across Indian forests and link it to soil dryness and heat stress, while confirming earlier findings that rising greenness in forests isn’t translating into greater carbon uptake.
This weakening of forests represents a fresh challenge to India’s efforts at combating climate change through, among other actions, expanding forest and green cover, scientists at the Indian Institute of Technology, Kharagpur, who conducted the study, have said.
“Worryingly, we see the greatest declines in photosynthetic efficiency in some dense forest patches in the Western Ghats, the Eastern Ghats, and the western Himalayas,” said Jayanarayan Kuttippurath at the IIT Kharagpur’s Centre for Ocean, River, Atmosphere, and Land Sciences, who led the study.
India’s latest forest assessment, released by the Union environment ministry in December 2024, showed that the country’s forest area had increased by 1,445sqkm between 2021 and 2023, with forest and tree cover accounting for about 25 per cent of India’s land area.
The assessment had also estimated that India has already created an additional “carbon sink” of 2.29 billion tonnes compared to the base year of 2025, against the target of 2.5 to 3 billion by 2030.
The new findings put a question mark on the amount of carbon that forests will soak up.
Kuttippurath and research scholar Rahul Kashyap used data from satellite imagery and computational techniques to measure photosynthetic efficiency through leaf area or greenness and vegetation, along with data on soil moisture and heat stress.
They found what they have described as “hindered ability” of Indian forests to translate the greening into carbon uptake due to an average 5 per cent decline in photosynthetic efficiency — of the capacity of leaves to use carbon dioxide for energy and plant growth — between 2000-2009 and 2010-2019.
Their study, just published in the journal Resources, Conservation, and Recycling, has linked this decline in photosynthetic efficiency to lowered water use efficiency driven by marked soil drying and enhanced evaporation under warmer temperatures.
“Such conditions are leading to an overall deterioration of forest health,” Kuttippurath told The Telegraph. Their analysis has estimated that only 16 per cent of Indian forests exhibit “high integrity” — in other words, function as healthy forests should.
Two years ago, climate researcher Subimal Ghosh and his colleagues at IIT Bombay had also found that adding greenness does not lead to higher carbon uptake. Their independent study had revealed a 6 per cent decrease in plants’ capacity to produce mass despite an overall 6 per cent increase in a measure of the overall leaf area.
In the years ahead, Kuttippurath and Kashyap have said, deforestation and damage to forests driven by climate change, extreme weather episodes, expanding agriculture and commercial plantations could turn parts of India’s forests into savanna-like landscapes, the researchers have cautioned.
“There is an urgent need to protect native forests, manage forest resources responsibly, adopt smarter forest management, cut carbon emissions sharply, engage in science-guided tree plantation efforts — all essential steps towards India’s goal of net-zero emissions by 2070,” Kashyap said.