The group has painstakingly profiled aquatic biodiversity in Trishuli, Karnali, Gandaki, and Mahakali rivers using eDNA, developing extensive datasets to monitor the long-term health of the river systems – building the country’s first fish DNA reference database in the process. “Before we started working, the fish species database from Nepal was almost non-existent,” says Karmacharya.

Efforts to build the reference DNA contributed to embedding eDNA in the Trishuli Assessment Tool, a standardised method for sampling freshwater aquatic biodiversity for use in planning hydropower projects, with eDNA providing an image of species that live in the environment in more detail than other methods. Next, the team will be profiling the eDNA of important Nepal glaciers for the first time.

Policymakers and ecosystem managers looking to restore the Deepor Beel, a wetland of international importance under the Ramsar Convention in the Indian state of Assam, have been relying on eDNA studies to glean a snapshot of its biological diversity, which is rapidly changing due to the effects of climate change and rising anthropogenic pressures including pollution. Understanding the impacts of anthropogenic changes on fish in Deepor Beel has been central to ensuring livelihood security for the 150 families of mostly fishers the wetland supports.

The eDNA dataset, which covers fish species and microorganisms in the wetland, is the first collected for any Ramsar-listed wetland in northeastern India. “eDNA was the best option because we can’t afford to lose time in taxonomically identifying fish species [as new species identification requires specialist knowledge],” says Punyasloke Bhadury, a scientist at the Indian Institute of Science Education and Research Kolkata.

“We need to do more surveys to refine the dataset and truly capture all the species in the wetland [before even more of them go extinct],” adds Rajkumari Nikita, a PhD student at the institute’s Centre for Climate and Environmental Studies, who conducted eDNA surveys at Deepor Beel.

Scaling up eDNA surveys

eDNA is well-suited to the Himalayan ecosystems, especially transboundary rivers and remote terrains, to understand ecosystem health by using species populations as an indicator, notes Chettri.

Biologist Pushpinder Singh Jamwal and researchers at the University of Milano-Bicocca recently tested the results of eDNA surveys that identified the presence of Eurasian otters (Lutra lutra) in the Indus river drainage of Ladakh in the Trans-Himalayas against a traditional field survey that uses direct otter sightings. In their study, otter DNA was found at 73 per cent of the sites, whereas the species was seen at just 53 per cent.

“Beyond detection, the study provides new insights into the ecology of the Eurasian otter in the Indian Trans-Himalayas, [which is] necessary for framing comprehensive conservation strategies that go beyond mere presence/absence assessments,” Jamwal notes, such as developing early warning systems for changes in otter populations or habitat quality.

In 2022, a pilot eDNA survey in the Mangdechhu river basin in south-central Bhutan commissioned by the country’s Department of Forests and Park Services uncovered the presence of endangered and vulnerable species including the white-bellied heron, tiger and gaur. The next step is incorporating eDNA into species conservation in Bhutan, says Kezang Yangden, Conservation Director at WWF-Bhutan, which assisted in the survey.

However, the lack of capacity to conduct eDNA analyses in Bhutan – in terms of infrastructure, equipment, and expertise – is a major challenge in advancing the technology’s application in the country, she notes.

Extreme weather conditions in the Himalayas can also disrupt the research environment, impacting the effectiveness of sampling and the quality of collected samples, adds Jamwal. Limited infrastructure present in many Himalayan areas can hinder the setting up and maintenance of research facilities for such surveys.

Chettri likewise emphasises the need for systems for data archiving, sharing, and analysis and interpretation of eDNA findings. Research institutions in the Himalayas still lack the required expertise, and as an emerging tool, the costs of sampling and testing eDNA are still high – but is likely to decrease if widely used, he adds.

This story was published with permission from The Third Pole.