India lost 18 sq km of forest for every 1 sq km it gained between 2015 and 2019, a new study by the Indian Institute of Technology Bombay (IIT Bombay) has revealed.

The research, led by Professor Raaj Ramsankaran from IIT Bombay in collaboration with Dr Vasu Sathyakumar and Sridharan Gowtham from SASTRA Deemed University, used digital forest cover maps from the Copernicus Global Land Service (CGLS) Land Cover Map to assess forest cover changes during this five-year period.

All states in India recorded a net loss in forest cover during this time, according to the research. While 56.3 sq km of forest was added, a massive 1,032.89 sq km was lost, with Tamil Nadu and West Bengal together accounting for nearly half of that loss.

One of the most critical observations of the study was the quality of new forest cover being added. More than half of the newly-added forests were islets or fragmented, lacking what the researchers call “structural connectivity”, the continuous spread of green that sustains biodiversity.

“Our results clearly show that most of the newly added forests during 2015 to 2019 were islets, highly fragmented and ecologically vulnerable patches,” said Dr Sathyakumar. “There is a need to move beyond the current quantity-based afforestation approach and explicitly incorporate structural connectivity into forest planning.”

Such connectivity is crucial for the resilience and regeneration of ecosystems. Large, continuous forest tracts support diverse wildlife, maintain ecological balance, and are more resilient to both natural and human-made disturbances. Fragmented forests, by contrast, disrupt animal movement and survival.

The report said that species like the tiger, which require large territories to hunt and breed, struggle to survive in fragmented forests, increasing the chances of human-wildlife conflict.

Andhra Pradesh, Tamil Nadu, Karnataka, and Rajasthan, which together accounted for nearly half of the total 56.3 sq km added during the study period. But this gain was offset by losses, especially in Tamil Nadu and West Bengal, responsible for nearly 50 per cent of all forest area lost.

The research team has proposed a new framework using remote sensing data and open-source tools to map and monitor forest connectivity across the country, at both state and national levels.

The study’s findings diverge from the Forest Survey of India (FSI) reports, which have reported an overall increase in forest cover in recent years.

But that’s because the FSI and CGLS use different definitions and datasets.

FSI defines forests as areas with at least 10 per cent tree canopy cover, using satellite imagery with a 23.5-meter resolution.

The CGLS dataset uses a 15 per cent canopy threshold and has a 100-meter resolution.

“Since FSI reports do not include forest connectivity assessments, direct comparisons aren't possible,” said Dr Sathyakumar. “However, our data source has a globally validated accuracy of over 85 per cent, making our connectivity results reliable. If FSI's data were made available in GIS-compatible format, our methodology could be readily applied to it.”

This study adds to a growing body of evidence that points to India’s ecological crisis.

According to the 2024 Nature Conservation Index (NCI), India ranked 176 out of 180 countries, with a score of 45.5, placing it among the worst five nations globally for biodiversity conservation. Only Kiribati, Turkey, Iraq, and Micronesia fared worse.

“India is one of the world’s mega-diverse countries, with about 7–8 per cent of the world’s documented species spread over only 2.4 per cent of total land area,” said the NCI citation, published on the BioDb website.

The Nature Conservation Index used 25 indicators to evaluate countries across land management, threats to biodiversity, governance capacity, and future trends. India’s low rank indicates severe habitat loss, rising pollution, and declining wildlife populations. The report also cited insufficient conservation legislation as a key factor.

Together, the IIT study and the NCI report send a clear signal that India's forests may be expanding on paper, but the reality on the ground is a growing threat to biodiversity.