Why in news?
A new monitoring campaign has raised concern about unstable slopes inside Uttarakhand's Nanda Devi Biosphere Reserve. The New Indian Express reported on 9 October that mapped landslide-prone zones had nearly doubled since the 2015 survey. It also described a developing glacial lake at about 5,000 metres, held behind a ridge of glacial debris. These are findings attributed to the 2026 campaign, not a prediction that a flood is certain. They matter because restricted human access can protect wildlife without insulating mountains from changing ice and slope conditions. The immediate question is how to monitor those changes before they threaten ecosystems and communities downstream.
Two protected parks within a larger landscape
The reserve occupies a high Himalayan landscape in Uttarakhand, with Nanda Devi and Valley of Flowers National Parks at its core. The United Nations Educational, Scientific and Cultural Organization, or UNESCO, recognises the two parks as one World Heritage property. Nanda Devi entered the list in 1988; the property was extended to include Valley of Flowers in 2005. This is different from the wider biosphere reserve's recognition under UNESCO's Man and the Biosphere Programme in 2004. The designations overlap geographically, but they describe different conservation arrangements.
The biosphere reserve includes forests, community land, agricultural areas, grassy slopes, alpine meadows and snow-covered terrain. Its elevation rises from about 1,800 metres to Nanda Devi's 7,817-metre summit. This range creates contrasting habitats within a relatively compact mountain region. Alpine meadows, locally called bugyals, support herbs and low shrubs above the main forest belt. The wider reserve also includes inhabited areas, so it should not be imagined as an entirely people-free enclosure.
Why the valleys matter
Nanda Devi's steep mountain basin drains through the Rishi Ganga gorge. The Rishi Ganga joins the Dhauliganga, which in turn meets the Alaknanda. This connected drainage explains why a high-altitude disturbance can have consequences far below its starting point. Water, sediment and broken rock can move through narrow valleys towards downstream infrastructure. The nearby Valley of Flowers offers a contrasting, gentler alpine landscape. Both parks support important mountain wildlife, including snow leopards, musk deer and bharal, or blue sheep.
What a growing glacial lake can change
A retreating glacier can leave depressions that fill with meltwater. Some lakes are retained by a moraine, a ridge of rock and other debris deposited by ice. Such a barrier is not equivalent to an engineered concrete dam. If it fails, stored water can escape rapidly and produce a glacial lake outburst flood. Rock or ice falling into a lake can also disturb the water and its retaining barrier. The danger depends on the lake, surrounding slopes, dam condition and downstream exposure, rather than its mere existence.
The Indian Space Research Organisation uses repeated satellite images to track Himalayan lake formation and expansion. Satellite coverage is particularly valuable where field access is difficult or dangerous. However, measuring an expanding water surface does not alone establish when a barrier might fail. Field observations and terrain analysis help explain what the images mean. Monitoring therefore needs to connect changing lake dimensions with the condition of the enclosing land and the valleys below.
Not every mountain flood begins in a lake
The February 2021 Chamoli disaster illustrates another mechanism. Research published in Science identified a large collapse of rock and glacier ice from Ronti Peak. The resulting avalanche transformed into a highly mobile debris flow through the Ronti Gad, Rishiganga and Dhauliganga valleys. It was not simply an overflowing glacial lake. This distinction matters for preparedness: monitoring only water bodies would miss dangerous changes in steep rock faces and ice-covered slopes.
Restricted access has helped retain relatively undisturbed habitats in the two national parks. UNESCO's assessment nevertheless identifies infrastructure and hydropower development in the buffer landscape as management concerns. Conservation monitoring and hazard monitoring answer related but different questions. More wildlife observations can indicate ecological recovery while unstable terrain creates a separate danger. Neither finding cancels the other.
Conclusion
The reported changes call for closer observation of slopes, ice, lakes and their downstream connections. They do not show that every protected valley faces an imminent catastrophe. Nanda Devi's conservation success must be supported by an equally clear understanding of physical hazards. Protecting habitats and reducing exposure to dangerous mountain flows are complementary responsibilities, not competing interpretations of the same landscape.