Manu National Park

Listen for a moment. Under the hum of insects there is a deeper layer of sound — the drip of water from leaves high above, the slow creak of a branch, a call that rises and falls somewhere out of sight. The air is warm and heavy. It smells of wet soil, rotting fruit and river mud. You are standing in one of the most biologically rich places on Earth, and almost all of it is hidden from you.

This is Manu National Park, in the southeast of Peru. It stretches across parts of the Cusco region and the neighbouring region of Madre de Dios. Peru created the park in 1973. UNESCO named it a biosphere reserve a few years later and then a World Heritage Site in 1987. On a map it looks like a single green block. On the ground, it is something much stranger — a staircase of entirely different worlds.

Here is the first thing most visitors miss. Manu does not sit at one altitude. Its upper edge climbs to cold Andean grassland at roughly four thousand metres, where frost forms at night. Its lower edge drops to lowland Amazon rainforest only a few hundred metres above sea level. Between them lies a long slope of cloud forest. Very few protected areas anywhere cover such a complete vertical journey, from mountain grass to jungle river, inside one boundary.

If you came by road from Cusco, you travelled down that staircase yourself. The route crosses a high pass and then falls away into the clouds. Within a few hours the bare hills give way to dripping forest. Tree ferns appear beside the road. Mosses hang from every branch like green wool. Orchids and bromeliads — plants that grow on other plants rather than in soil — cover the trunks. The temperature rises with every bend.

The cloud forest is the home of a bird that many people come specifically to see. It is the Andean cock-of-the-rock, Peru's national bird. The males are a flaming orange-red with a crest that hides the bill. At dawn they gather in groups and perform for the females. They bob, flap and make loud squawking calls. It is a noisy, almost comical show, and it takes place in the half-light before the mist lifts.

Lower down, the rivers take over. Travel in the lowlands of Manu happens mostly by long wooden boat. The water is brown and fast, heavy with sediment from the Andes. Sandbanks appear and disappear with the seasons. On the beaches you may see the tracks of capybaras — the world's largest rodent, about the size of a large dog — and sometimes the broad, rounded prints of a jaguar that walked there in the night.

Now for the second surprise. The scientific numbers in this park are difficult to believe. Researchers have recorded around a thousand bird species in and around Manu. That is roughly one in ten of all the bird species on the planet, in one protected area. Scientists continue to find insects, frogs and plants here that have never been formally described. Much of the forest canopy, high above your head, has still never been properly studied.

Along the rivers you may also find oxbow lakes. These are curved, quiet lakes that form when a looping river bend gets cut off from the main channel. They are calm and dark, edged with floating plants. Some of them are home to giant otters. These animals can grow to the length of a tall adult. They live in noisy family groups, and they hunt fish together, surfacing with loud snorts and screeches.

Another scene draws people out of bed long before sunrise. In parts of the Manu region, macaws and parrots gather at exposed riverbanks of clay. They land in hundreds, red and blue and green, and they eat the soil itself. Scientists still debate the exact reason. One theory says the clay helps neutralise toxins from the seeds they eat. Another says it supplies salt that is scarce in their diet. Either way, the sound is enormous.

Manu is not an empty wilderness. People have lived in this forest for a very long time. Indigenous communities, including the Matsigenka, have homes inside and around the park. There are also groups living in voluntary isolation, with no regular contact with the outside world. For this reason, the largest part of Manu — its core zone — is closed to tourists. Only researchers and the people who already live there may enter it.

Visitors travel instead through the zones set aside for controlled access, usually with licensed guides and operators. This can feel restrictive at first. But it is one reason the forest here remains so intact. In the late nineteenth century, the rubber boom brought violence and disease to much of this part of the Amazon. Manu's remoteness, and later its protection, helped keep large parts of it far from roads, logging and settlement.

The forest also teaches patience. Animals here are rarely posed in plain view. You might wait an hour and see only leaves. Then a troop of monkeys crosses the canopy in a rush of shaking branches. A guide may point at what looks like bark and show you a resting moth or a frog. The best sightings often come quietly, on foot, in the early morning or just before dark, when the forest is most active.

At night the forest changes again. The birds go quiet and the frogs and insects take over. The sound becomes a thick, constant pulse. Eyes reflect in the beam of a torch — spiders, caimans along the riverbank, perhaps a night monkey in the trees. Even sleeping in a lodge here, with only a screen between you and the forest, you are surrounded by life that never fully stops moving.

So before you move on, pause and look around you once more. Notice how many shades of green you can count. Notice the layers — the ground, the trunks, the vines, the canopy, the sky beyond. Somewhere above you, something is almost certainly watching. As you walk or float away from here, keep listening. In Manu, the forest usually shows itself to those who are quiet enough to hear it.