The Sundarbans is the only mangrove forest on Earth with tigers in it, and they swim. It covers roughly 10,000 square kilometres of tangled trees and hidden creeks, split between Bangladesh and India. This is the delta where the Ganges, Brahmaputra and Meghna empty into the Bay of Bengal, so the forest stands on shifting silt rather than solid ground. Twice a day the tide climbs and drowns half of it. When the water falls back, thousands of pencil-thin breathing roots stand up out of the exposed mud, which is how the trees get air into waterlogged soil. Around two hundred tigers still live here, along with spotted deer, saltwater crocodiles up to six metres long and the rare Ganges river dolphin. The name may come from the sundari tree that grows out of the brackish mud, or simply from sundarban, beautiful forest in Bengali.
You can only enter by boat. A launch threads the narrow channels for two or three days, and the scene changes at every bend — dense green walls, mudflats printed with pugmarks, kingfishers going off like sparks over the water. At dawn a low mist sits on the creeks and sound carries a long way. By dusk the light turns warm on the flats where deer come down to feed. Tigers here do kill people, and the fishermen and woodcutters who work these creeks know it. The same trees that hide the tiger protect everyone inland: this wall of mangrove blunts the cyclones and storm surges that come in off the Bay of Bengal. Rising seas and creeping salt are now pushing at the forest from both sides. Access is by permit, and every boat carries a forest department guard.