The world ignored warnings about the Three Gorges Dam until it became an environmental nightmare. It cannot afford to repeat that mistake with China’s super-dam near the Indian border — a project whose ecological fallout will ripple globally.

Brahma Chellaney, Special to The Globe and Mail

Last month, China officially acknowledged that it is constructing the world’s largest dam, on the Yarlung Zangbo River (better known as the Brahmaputra) in Tibet, just a few kilometres from the Indian border.

Though satellite imagery had suggested activity at the site for some time, Premier Li Qiang‘s July announcement marked Beijing’s first open admission of the megaproject, which will have far-reaching environmental, geopolitical and hydrological consequences across Asia and beyond. For proof, just look at the current largest dam in the world, China’s Three Gorges Dam. It has proved to be an environmental nightmare; its mammoth reservoir has triggered landslides, increased seismic activity and even slightly slowed Earth’s rotation.

One would have expected such a revelation to trigger strong international reactions. Yet, despite the dam’s extraordinary implications, the world has stayed silent.

China’s new super-dam seeks to exploit the immense drop in elevation as the Brahmaputra descends from the Himalayas before curving into India. This geologically unstable, ecologically sensitive zone lies close to the heavily militarized border with India’s Arunachal Pradesh state – a territory almost three times the size of Taiwan that China claims as its own.

Thanks to its 1951 annexation of the resource-rich Tibetan Plateau – the source of 10 major Asian rivers – China is the origin of cross-border flows to more countries than any other nation. Since the 1990s, its frenzy of dam-building has shifted from internal rivers to international ones, without consultation or transparency.

China already boasts more large dams than the rest of the world combined, and it has emerged as the main obstacle to institutionalized co-operation on shared water resources in Asia. It has no water-sharing treaty with any downstream neighbour because it asserts “indisputable sovereignty” over waters within its borders, including claiming the right to divert as much as it wishes. In this way, water is not merely a resource for China, but a strategic instrument.

The havoc caused downstream by China’s 11 giant dams on the Mekong – which sustains Thailand, Laos, Cambodia and Vietnam – has not deterred it from building more on that river. Against this backdrop, China’s colossal Brahmaputra project threatens to accelerate environmental degradation on the Tibetan Plateau, which is warming at twice the global average rate. That degradation could, in turn, disrupt Asian monsoons, weather and climate patterns.

With its towering height rising into the troposphere, the Tibetan Plateau profoundly shapes these patterns, influencing even the Northern Hemisphere’s atmospheric general circulation – the vast system of winds that transports warm air from the equator toward higher latitudes, helping to define different climate zones.

Tibet’s environmental fragility already has planetary implications, including accelerating biodiversity loss. Faster glacial retreat and permafrost thaw threaten to undermine the plateau’s role as Asia’s “water tower.”

Besides destabilizing a delicate Himalayan ecosystem, China’s super-dam – located on a geologic fault line – stands out as the world’s riskiest megaproject. It represents a potential water bomb for millions downstream. The Brahmaputra is a lifeline for northeastern India and for Bangladesh, the world’s most densely populated major country, and the super-dam will disrupt natural river flows, threatening food and water security for millions downstream.

In an era of increasing water stress and climate volatility, China can now deploy water as an instrument of coercion. The new dam will hand Beijing a potent new lever against India, its strategic rival. Should bilateral tensions with India rise, China could regulate or disrupt flows – whether by withholding water during the dry season, releasing excess water in flood season, or altering ecosystems. Even without hostile intent, unilateral control of river flow introduces long-term uncertainties for downstream communities, infrastructure planning and disaster management.

Yet India, in the absence of credible diplomatic options, has responded to China’s acknowledgment with restraint, voicing “concern” while stressing the “need for utmost transparency.” Other powers, meanwhile, have remained conspicuously silent, wary of offending Beijing. Such silence may appear low-risk today, but as the world’s largest dam rises in the fragile Himalayas, inaction carries long-term costs – not just for Asia’s water security, but also for the planet’s ecological balance.

The international community ignored warnings about the Three Gorges Dam until its consequences became undeniable. It should not repeat that mistake. By averting its gaze now, the world risks not only destabilizing South Asia’s water and food security but also undermining the environmental stability of an entire continent – with ripple effects that will be felt worldwide.

Brahma Chellaney is a geostrategist and the author of nine books, including the award-winning Water: Asia’s New Battleground.