Chinese Premier Li Qiang called it a “project of the century,” as he stood alongside high-ranking officials to announce the construction of the 1.2 trillion yuan (about $168 billion) infrastructure project along the lower reaches of the Yarlung Tsangpo river in July. The state-run Xinhua News Agency hailed the world’s biggest planned hydropower dam as a “low-carbon development … a safe project that prioritizes ecological protection.”

But the sheer scale of the dam carries immediate and long-lasting consequences for planetary health. Environmentalists say the Yarlung Tsangpo creates unique hydrothermal conditions when it collides with the eastern Himalayas, resulting in the world’s northernmost tropical rainforest, home to diverse large cats and ungulates, as well as some of Asia’s largest and ancient trees. Many new species are still being discovered in the area, including the white-cheeked macaque, found around 2014.