Hindu Kush Himalaya, Bangladesh, and the Climate Reckoning Ahead 

Thousands of kilometres from the coastlines and river deltas of Bangladesh, among some of the highest peaks on earth, lies a secret that governs much of this nation’s destiny. The Hindu Kush Himalaya �" a vast arc of mountains stretching across eight countries �" feeds the rivers that fill Bangladesh’s fields, sustains the monsoon that waters its crops, and now, as the climate unravels, sends signals of danger that Dhaka can no longer afford to ignore.

A Mountain System Like No Other: The Hindu Kush Himalaya, commonly abbreviated as HKH, is not a single mountain range but a sprawling system of interconnected ranges spanning approximately 3,500 kilometres. It arcs across Afghanistan, Pakistan, India, Nepal, Bhutan, China, Myanmar, and Bangladesh, encompassing some of the world’s most dramatic terrain and most precious ecological assets. The region is home to more than 240 million people living in its hills and mountains, with a further 1.65 billion people downstream dependent on what flows from it.

Scientists and policymakers sometimes call the HKH the “Third Pole” of the Earth. It holds the largest concentration of glaciers and permafrost outside the Arctic and Antarctic, storing freshwater in quantities that are almost impossible to comprehend. Ten of Asia’s great river systems originate here. From these peaks flow waters that sustain roughly a quarter of humanity, irrigate vast agricultural plains, and underpin entire civilisations.

The International Centre for Integrated Mountain Development (ICIMOD), the foremost research body on the HKH, has described the region as carrying value not just for mountain communities but for the whole world. Yet, as their landmark Hindu Kush Himalaya Assessment of 2019 noted, the region remains poorly understood, its knowledge scattered and rarely reaching those who need it most.

The Rivers That Bind Us: Bangladesh’s relationship with the HKH is, above all, a relationship of water. The country sits at the confluence of three enormous river systems, all of which trace their origins to the Himalayan and sub-Himalayan ranges.

The Ganges, known in Bangladesh as the Padma, begins its journey at the Gangotri glacier high in the Indian Himalayas. Fed by snowmelt and monsoon rain, it travels thousands of kilometres before splitting into multiple distributaries across Bangladesh’s landscape. It carries the silt that has built the Bengal delta over millennia, the same silt that makes Bangladesh’s soil among the most fertile on the planet.

The Brahmaputra, called the Jamuna after it crosses into Bangladesh from Assam, is even more dramatic in scale. It originates on the Tibetan plateau, circles the eastern flank of the Himalayas, and pours into Bangladesh with a volume that few rivers on earth can match. During peak monsoon season, the Jamuna is one of the widest rivers in the world. It carries an enormous sediment load and is responsible for the constant reshaping of Bangladesh’s riverine landscape, eroding one bank and depositing new land on another with a restlessness that both threatens and creates.

The third great system, the Meghna, collects the waters of the northeastern catchments, including drainage from the hills of Meghalaya and Tripura, before joining the combined flow of the Padma and Jamuna in the heart of Bangladesh. Together, these three systems form one of the world’s most complex and powerful river networks, draining a catchment that stretches far into the Himalayan interior.

This hydrological lifeline means that whatever happens in the mountains eventually happens in Bangladesh. The HKH is not a distant abstraction. It is the source code of this nation’s geography.

When the Mountains Begin to Melt: Climate change is now rewriting the rules that have governed this relationship for centuries. The HKH region is warming at a rate faster than the global average, a phenomenon scientists call elevation-dependent warming. According to research published by ICIMOD and cited at the HKH to Glasgow webinar in December 2020, a 1.5 degrees Celsius rise in global average temperature is projected to translate into a 2.1 degrees Celsius increase within the HKH itself by the end of the century. This acceleration of warming at altitude has consequences that ripple far beyond the mountains.

The glaciers of the HKH are retreating. In the short term, this produces more meltwater, swelling rivers during certain seasons. But the long-term trajectory is one of depletion. When glaciers shrink to the point where they can no longer sustain dry-season flows, the rivers they feed will diminish. The predictability that farmers and fishermen in Bangladesh have built their livelihoods around will erode.

The consequences are already visible. Glacial lake outburst floods, where ice-dammed lakes rupture under pressure from accumulating meltwater, are becoming more frequent. These catastrophic releases send walls of water and debris downstream, devastating communities along river corridors. While Bangladesh itself sits far from the glacier lakes, the ferocity of water pulses entering its rivers is increasing.

Monsoon behaviour is also changing. The HKH plays a critical role in shaping South Asian monsoon patterns, and as the thermal dynamics of the mountains shift, so too does the distribution of rainfall. For Bangladesh, this means greater variability: intense rainfall concentrated in shorter windows, causing flash floods, alongside prolonged dry spells that deepen drought stress in the north and northwest of the country.

Bangladesh at the Receiving End: Bangladesh is already one of the world’s most climate-vulnerable nations, and the changes underway in the HKH compound every challenge it faces.

Flooding affects tens of millions of people each year. As the upstream catchment becomes more erratic, the timing, intensity and geographic spread of floods in Bangladesh is shifting. The riverbanks that communities have lived beside for generations are being reconfigured at accelerating rates. Char dwellers, who live on the sandbars that rise and fall with river behaviour, face increasing displacement. When the Jamuna runs higher and harder, entire islands vanish.

In coastal Bangladesh, the situation is compounded by sea level rise. As floodwaters arrive in greater volumes from the north while the ocean presses inward from the south, the delta is caught in a squeeze. Saltwater intrusion is advancing inland, contaminating drinking water sources and destroying the agricultural productivity of coastal soils. In the Sundarbans, the largest mangrove forest on earth, both the ecosystem and the millions who depend on it are under simultaneous pressure from above and below.

Food security, always precarious for a dense population on a flood-prone delta, is increasingly threatened. Bangladesh’s rice cultivation is deeply seasonal and water-dependent. Disrupted irrigation schedules, unpredictable flooding during harvest seasons, and saline contamination of farmland all erode the foundation of the country’s food system. The people least able to absorb these shocks, small farmers, women in rural households, the landless poor, bear the greatest burden.

Pathways to Adaptation: None of this is inevitable in its worst form. There are meaningful steps that Bangladesh, alongside its neighbours in the HKH region, can take.

Regional cooperation is the most important and most underdeveloped tool available. The rivers of the HKH do not respect national boundaries, and neither do the risks they carry. Bangladesh has a direct interest in building robust data-sharing and early warning systems with India, Nepal, Bhutan and China. When a glacial lake in Bhutan is at risk of bursting, downstream communities in Bangladesh deserve to know. Real-time hydrological monitoring, jointly managed across borders, can give people precious hours or days to prepare.

Within Bangladesh, investment in climate-resilient infrastructure must accelerate. River embankments need to be designed for a future of higher and more erratic flows. Urban drainage systems in cities like Dhaka, Sylhet and Chattogram must account for the more intense rainfall events that climate projections indicate. Floating agricultural systems, which communities in Barisal have practised for generations, deserve scaling and research investment as a model of adaptation to permanent inundation.

Ecosystem-based adaptation, working with natural systems rather than against them, offers significant potential. The restoration of wetlands, haors and floodplains as natural buffers against flood peaks can complement hard engineering. Mangrove restoration in the coastal zone provides both storm surge protection and biodiversity value.

Bangladesh must also exercise its diplomatic voice with greater insistence. As a downstream nation with limited influence over upstream water management decisions in India and China, the country must use multilateral forums, including United Nations platforms, SAARC, and climate negotiations, to press for transboundary water governance frameworks grounded in equity and shared risk.

The Hindu Kush Himalaya is not simply a backdrop to South Asian geopolitics. It is a living, dynamic system upon which Bangladesh’s survival, in its current form, depends. As climate change reshapes those mountains, the effects travel southward with the rivers, arriving at the doorsteps of millions who have never seen a glacier but whose futures are written in ice.

Bangladesh has demonstrated remarkable ingenuity in living with water. The coming decades will demand that ingenuity be matched by science, by cooperation, and by a political will proportionate to the scale of what is at stake.