| News / World News |
Bhutan rapidly losing glaciers and snow cover
Bhutan’s Punatsang Chhu river basin, spread over 10,655 square kilometres, has lost 51 per cent of its snow and glacial cover over the last 20 years (1996—2017) as a result of climate change and human activity, says a new study.
Bhutan Himalayas. Photo: NASA/GSFC/METI/ERSDAC/JAROS and U.S./Japan ASTER Science Team
Mountain glaciers worldwide lost mass at an average rate of 220 gigatons per year during 2006— 2015, equivalent to 0.61 millimetres sea level rise annually.
The resulting decline in the extent and duration of snow cover disturbed the stability of high-mountain slopes, according to a special report released September 2019 by the Intergovernmental Panel on Climate Change.
In Bhutan, the loss in snow cover has exposed rocky outcrops and bare land in a major river basin which makes up almost a third of the Himalayan country’s land area (38,394 square kilometres), stretching from the glaciers in the north-western district of Gasa, moves southwards through the districts of Punakha, Wangdue, Tsirang and Dagana and then enters India’s West Bengal state.
The study site showed increase in maximum temperature by about one degree Celsius and minimum temperatures by about 0.5 degrees Celsius.
The researchers detected downward changes in seasonal average rainfall during the same period of study, decreasing from a high of about 800 millimetres to 400 millimetres per annum, which may have affected snow and glacier cover in the higher mountain reaches of the study area.
The study further shows that land cover changes have also led to significant alterations in agro-ecological landscapes, posing risks to the sustainability of the country’s hydro-power plants and agriculture.
The exposed lands, being rocky, cannot support cultivation despite the small gains for expanding alpine summer crops (mostly vegetables and crops like barley) in high-altitude natural pastures and meadows.
The adverse implications of surging rock outcrops and bare lands include the likelihood of an increased albedo effect (a measure of how much of the sun’s energy is reflected back into space), leading to heat accumulation, land erosion and glacial lake outburst flood incidents, leading to flooding of downstream valleys and settlements.
Human activities also lead to heat accumulation in the mountain valleys, which causes winter snow to melt fast, not staying even for a few days as compared to in the past.
For Bhutan, land cover changes could also be due to forest land conversion into non-forestry uses, including for agriculture, construction activities, urbanisation, rising population and expanding vehicular traffic.
The study findings provide evidence of the way land cover changes are triggering shifts in climatic patterns due to climate change and human interferences with the natural systems. (SciDev.Net)
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