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Climate change impact on extended Hindu Kush-Himalayan region

Mahfujur Rahman
NOW all conscious people know at least some common consequences of global warming, the first and foremost being melting of glacier and sea level rise as its result Mountains occupy 24% of the global surface area and are home to 12% of the world's population (ICIMOD, 2008). Mountain regions of this planet are not only vulnerable to climate change but also areas to visualize the impact of climate change since measuring the melting snow caps helps us understand the glacial retreat rate linked with climate change. The superb example of this is the Hindu Kush-Himalayan (HKH) region.
HKH range spans over 4.3 million km2 and the region includes areas of eight countries: Afghanistan. Pakistan, Nepal, Bhutan, China, India, Bangladesh and Myanmar. Few places on Earth can match the breathtaking splendour of the Himalayas. It contains varied geographical terrains and many unparalleled characteristics. Its towering peaks and secluded valleys have inspired naturalists, adventure seekers and spiritualists for centuries. Its diverse
landscapes harbour rare creatures like red pandas, snow leopards and onehorned rhinos.
Although this region has been romanticized as a mythical paradise, it is fragile now facing many, challenges. Climate change is melting its mountain glaciers. It is often referred to as the Third Pole' and the 'Water Tower of Asia,' as it stores a large volume of water in the form of ice and snow, and regulates the flow of the 10 major river systems in the region. But this storehouse is in danger now.
HKH region is considered to be the mountainous area of Asia expanding from south to the central Asia but extended HKH incorporates the adjacent river basins also.
Both direct instrumental records and environmental proxy records indicate that historical and recent changes in climate in many mountain regions of the world are often greater than those observed in the adjacent lowlands. Likewise, the rates of warming in the HKH region are significantly higher than the global average. The first and foremost effect of global warming is the melting of glacier - the snow line will change by glacial retreat. The change In snow line of HKH region due
to global warming will also affect the environment and livelihood of people in its river basins.
Himalayan glaciers accumulate most of their snow in summer from “solid" mon-soonal precipitation. As the atmospheric temperature continues to rise, the snowline (zero temperature line) continues to shift toward higher altitudes leading to more rain (Hasnain 2002, Kadota et al. 1993). Actual and potential changes in climatic parameters can have strong impacts on the cryospheric: a change in the snowline, change in duration of snow cover, an increase in cryogenic hazards such as ice and snow avalanches, glacier recession, formation and break-out of moraine-dammed lakes, etc. Trans-boundary effect More immediately, as the glaciers retreat, glacial lakes form behind some of the now exposed terminal moraines at elevations ranging from 3000 masl in the west to 5000 masl in the east of the region. Rapid accumulation of water in a glacial lake can lead to a sudden breaching of the unstable moraine dam. This results in the discharge of huge amounts ofwater and debris, a form of flash flood known as
glacial lake outburst flood (GLOF), which can have catastrophic effects downstream.
These high frozen reservoirs release their water at the top of the watersheds of the ten major rivers in the region. These rivers wind their way through thousands of kilometers of grazing, agricultural, and forest lands and are used as renewable sources of irrigation, drinking water, energy, and industry, serving some 1.3 billion people who live in the great river basins. On their journey, they recharge aquifers and many underground water sources. However, this glaciers are retreating in the face of accelerating global warming and are particularly vulnerable to climate change to the point that the long term loss of natural fresh water storage is likely to have severe effects on communities downstream.
The real threats
The eastern Himalayas has the largest concentrations of glaciers outside the polar regions - which hold vast stores of fresh water. The region's agriculture and power generation are fully dependent on the freshwater supply fed by the discharges of the Himalayan glaciers. Continued climate change is predicted to lead to major
changes in fresh water flows with dramatic impacts on biodiversity, people and their livelihoods.
The glaciers of the greater Himalayan region are nature's renewable storehouse of fresh water from which hundreds of millions of people downstream have benefited for centuries at the time in the year when it is most needed -the hot, dry season before the monsoon. One of the most visible impacts of climate change in the Himalayan region is the retreat of the glaciers, many at higher rates than in other mountain ranges.
Continued deglaciation could have a profound impact on the water in the ten large river basins originating in the HKH region. River discharges are likely to increase for some time due to accelerated melting, but the flow is then likely to be lower within next 30-50 years as the storage capacity of the glaciers will go down. The effects are likely to be felt most severely in the arid areas of the region specially parts of India which are already very dry.
Glacial lake outburst
Glacial lakes have formed in many places in the area at the foot of retreating valley glaciers. An inventory compiled by the International Centre for Integrated Mountain Development (ICIMOD) identified 8790 glacial lakes within selected parts of the HKH. Some 204 of the glacial lakes were considered to be potentially dangerous, that is liable to burst out leading to a glacial lake outburst flood (GLOF). There have been at least 35 GLOF events in
Bhutan, China and Nepal during the 20th century (ICIMOD, 2009). It is suspected that the number and intensity of GLOF will increase due to melting of Himalayan ice.
Increased hazards
The HKH is one of the most complex, dynamic, and intensive risk hotspots with earthquakes, floods, flash floods, landslides, droughts, and wild fires affecting it off and on. This is due to the physical and socio-economic characteristics of the region combined with the changing risk factors such as climate change, population growth, and economic demand. Floods and droughts are likely to increase as a result of a number of factors. An increase in seasonal change is predicted with more precipitation during the wet season leading to increased flood risk, and potentially drier dry season with increased risk for drought. Changes in the monsoon regime might lead to an overall increase in precipitation in some areas, and a decrease in others.
Hampered ecosystem Climate change is affecting ecosystem services by affecting forest type and area, its primary productivity, species populations and migration, occurrence of pests and diseases, and its regeneration. The increase in greenhouse gases is also affecting species composition and changing the ecosystem structure, which in turn affects ecosystem function. The interaction between elevated CO2 and climate plays an important role in the overall response of net primary productivity. Climate change will have a
profound effect on the future distribution, productivity, and ecological health of forests.
There could be a significant reduction in cryospheric ecosystems and their services. A major expansion of the tropical zones would cover most of the middle mountains and inner valleys, whereby the quality and quantity of ecosystem services are likely to change dramatically for the worse.
Affected well-being Climate change can affect people's wellbeing in a variety of ways. It is likely to exacerbate the existing food insecurity and malnutrition. Vector-borne diseases such as malaria and dengue fever are likely to move to higher altitudes. Water-borne diseases are also likely to increase with the increasing water stress accompanied by the lack of safe drinking water and basic sanitation in the region. Deaths and morbidity associated with extreme and erratic weather are also likely to increase. Climate change will have differentiated impacts which could be more severe for women, and the poor and the marginalized.
Conclusion
Hindu Kush-Himalaya region is highly vulnerable to the inevitable climate change. The mountain is melting in the monsoon at a higher rate and giving rise of numerous adverse effect like glacial lake outburst floods, impacting on water availability, disrupting ecosystem services, increasing the intensity of floods and drought and after all hampering the livelihood of over 1.3 billion people. Whatever we do to mitigate the climate change, global warming wall be advancing in the coming years. It will take about 100-200 years to eliminate the effect of already emitted anthropogenic green house gas if whole mankind stops emitting GHGs. So, measures must be taken now to adapt to the changed climatic condition. ICIMOD can play a vital role in the way of adaptation by research and disseminating the findings to the governments in the HKH region.
Mahfujur Rahman works as a Research Officer at Bangladesh Center for Advanced Studies (BCAS)