Bwindi Impenetrable Forest is exactly what its name says. Ferns, vines and moss-hung trees weave into a wall so thick that little daylight reaches the ground, and the name comes from a local word for darkness. It drapes the steep ridges of the Albertine Rift in southwestern Uganda, hard against the borders of Congo and Rwanda. Almost half the world's surviving mountain gorillas live in it — around 459 of the fewer than 1,100 left alive. This is one of Africa's oldest rainforests, growing here for roughly 25,000 years. While ice-age droughts stripped woodland off much of the continent, these slopes stayed wet, and much that could not survive elsewhere ended up here. Over 350 bird species, more than 200 butterflies and some 160 kinds of tree crowd its 320 square kilometres, which climb from 1,160 metres to above 2,600.
Reaching a gorilla family is hard-won. With a guide and trackers you climb slick, near-vertical paths through undergrowth that closes over your head, sometimes for six hours. Then you part a screen of leaves and a silverback of more than 200 kilograms is watching you with a calm, level gaze while juveniles wrestle in the branches. You get one hour, and it goes fast. Only about 160 permits are issued a day across the whole forest, and the limits worked: the gorilla count rose from roughly 400 in 2011 to 459 by 2018. That recovery carried a human cost, because the Batwa who lived in these woods for millennia were evicted when the park was created in 1991. Beyond the gorillas, the trees hide chimpanzees, forest elephants and birds found almost nowhere outside the Albertine Rift. Rain falls most months, the paths are mud, and nobody comes back clean.