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The Hoolock gibbon, one of humans’ closest evolutionary cousins, clings to survival in a fragile habitat in India—a 21-km wildlife sanctuary in Assam’s Jorhat district named after the ape itself. Over the past century, human encroachment has steadily tightened its grip on the sanctuary, which is home to over 219 bird species, six primate species (including the world’s largest troop of stump-tailed macaques) and much more. A railway track, laid in 1887, cuts through its core, while “tea gardens and human settlements” encircle its “semi-evergreen forests and evergreen patches”, as described by the state’s forest department website.
Remarkably, the Hoolock gibbon, India’s sole ape species, has managed to endure. A 2019 census conducted by the Wildlife Institute of India, Dehradun, recorded 125 individuals within the sanctuary. However, conservationists are sounding the alarm over two projects sanctioned in 2024: exploratory hydrocarbon mining approved just 13 km south of the sanctuary and the electrification of the railway track running through it. These projects could upend the delicate balance of the vulnerable ecosystem, jeopardising the future of the primate and the other biodiversity in and around the sanctuary.
The exploratory drilling site on the Assam-Nagaland border, while located outside the Hoollongapar Gibbon Sanctuary, falls within its 265-sq-km eco-sensitive zone (ESZ) and near the Dissoi Valley Reserve Forest. Part of a project by Vedanta’s subsidiary Cairn Oil & Gas to map hydrocarbon reserves in Jorhat, the site is among 35 locations identified for exploratory mining and occupies a critical elephant corridor. In August 2024, the project received approvals from Assam’s principal chief conservator of forests, the chief wildlife warden, and the Forest Advisory Committee of the Union Ministry of Environment, Forest, and Climate Change (MOEFCC). Subsequently, the National Board for Wildlife (NBWL), a statutory body overseeing wildlife conservation, inspected the site in November 2024 and granted conditional clearance on December 21, 2024. They stated that while the site is within the ESZ, it does not encroach upon any designated elephant corridor. “Neither the Elephant Corridor Report by the Wildlife Institute of India nor the forest records with the MOEFCC classify the site as a designated elephant corridor,” says Raman Sukumar, an NBWL member and honorary professor at the Centre for Ecological Sciences, Indian Institute of Science, Bengaluru. According to Nandha Kumar, Jorhat’s district forest officer, elephant movements in the nearby Dissoi Valley Reserve Forest are seasonal. “They come when the paddies are ripe for harvest. The corridor is relatively small and the drilling site is located at a distance from it. It should not harm the elephants,” says Kumar.
Environmentalists, however, oppose the project, arguing that the area has historically served as an elephant migration route since the era of the Ahom kingdom (1228-1826). “The site is undeniably part of an elephant corridor, and it was one of the reasons the ESZ was notified in 2019,” says Tridip Dutta, secretary of the Central Jorhat District Citizens’ Forum, which filed a public interest petition in the National Green Tribunal in November 2024 against the mining project and the electrification of the railway track. Dutta claims that of the 35 drilling sites, 10 are within 2 km of the ESZ boundary. “Even if the sites fall outside, their cumulative impact will be catastrophic,” he warns.
Sukumar argues that the drilling is purely exploratory, aimed at mapping hydrocarbon reserves, not commercial extraction. Additionally, the project must comply with strict conditions, such as real-time digital surveillance, minimal tree felling and pollution controls. “If there are no commercial plans, why conduct exploratory drilling in an elephant corridor?” asks Dutta. Concerns are also being raised about the broader impact of such projects. “Deep drilling often brings contaminants like heavy metals to the surface, and improper disposal can pollute surface and groundwater sources,” says Pinaki Sengupta, former head of the material science and technology division at Jorhat’s North East Institute of Science and Technology. The noise and light pollution from round-the-clock operations would further disrupt wildlife.
When Down To Earth visited Agsomuwa village, one of the sites where drilling began in 2023, residents shared their anxieties. “The company has leased our land for three years, but the compensation does not match the value of our paddy crops,” says one farmer, speaking on condition of anonymity. Flooding in 2023 exacerbated their worries, as mud and chemicals from the drilling site spilled into fields and ponds. While no immediate crop damage was reported, concerns about long-term toxicity remain. There is also resentment among the residents over the way the project was sanctioned. An elderly woman from the village says only those whose lands were acquired were consulted. “The rest of us only learnt about it after the deal between the company and the landowners was finalised. There was no public meeting before the drilling machines were set up, and now they produce constant noise,” she adds.
The electrification of the Lumding-Dibrugarh section of the Northeast Frontier Railway, a 1.65-km stretch of which runs through the Hoollongapar Gibbon Sanctuary, has also alarmed conservationists. The railway line, a vital link to Upper Assam, was upgraded to broad gauge in 1996-97 and sees around 40 trains daily. News of the electrification of the tracks was first confirmed in July 2024 through a Right to Information application filed by youth political groups, the Students’ Federation of India and the Democratic Youth Federation of India (DYFI). “We first protested at Mariani railway junction (which is nearest to the sanctuary) and submitted a memorandum to the railways on July 15, 2024, calling for the with-drawal of the proposal. This was followed by protests in front of the circle office. We also brought the matter to the no-tice of Jorhat’s Member of Parliament,” says Prarthana Bordoloi, of DYFI. Still, on October 9, 2024, NBWL approved the project. While electrical posts have been erected, the track is yet to be energised. “For years, there have been demands to divert the railway section outside the sanctuary because it breaks the canopy cover.
Instead, they are now electrifying the track,” says Pinakpani Borthakur, a resident of Meleng Lakhipur village outside the sanctuary. In July last year, Borthakur wrote to the state chief minister about the same.
Hoolock gibbons rely on tree canopies for movement. The sanctuary’s dense vegetation, including Assam’s state tree, Hollong, provides ideal conditions for their arboreal lifestyle. However, shrinking forests and widening canopy gaps threaten the gibbons’ survival. “Gibbons are fascinating not only because of their arboreal nature but also due to their human-like partner selection process,” says Narayan Sharma, assistant professor at Cotton University, Guwahati. “They are family-centric, with each family comprising 5-6 members. Individuals choose mates from outside their families,” he adds. This behaviour underscores the need for uninterrupted canopies.
Kumud Ghosh, a resident of Bheleuguri Ratanpur village outside the sanctuary, says the residents believe the canopy break has led to the separation of gibbon families for years and may have caused inbreeding depression. “A genetic study can prove it,” he says.
Dilip Chetry of Aaranyak, an Assam-based conservation non-profit, says rerouting the track 5.7 km south of the sanctuary is an easy solution to the problem. “This would protect the wildlife and facilitate future track expansion,” he says.
This was first published on the 1-15 February, 2025, Print edition of Down To Earth