Amanã was created by decree number 19.021 on August 4, 1998. It covers 2.35 million hectares - about 23,500 square kilometers, roughly the size of Belize - in the north-central part of Amazonas state. To its south and west, across the Japurá River, stretches the 1.12-million-hectare Mamirauá Sustainable Development Reserve, established in 1996 as Brazil's first reserve of this kind. To its east lies the 2.38-million-hectare Jaú National Park, inscribed by UNESCO as a World Heritage Site in 2000. Together, the three protected areas form one of the largest contiguous blocks of protected rainforest on the planet. In 2003, UNESCO expanded its listing to include Mamirauá, Amanã, and the Anavilhanas National Park under a single title: the Central Amazon Conservation Complex. Amanã is the bridge that makes the complex a continuous block.

Most of Amanã is terra firma - the high forest that never floods, growing on well-drained soils that hold century-old canopy trees. Around the lake and along the rivers the forest changes to várzea, which floods with whitewater from the Solimões, and to igapó, which floods with blackwater from tributaries that run clean and dark. Water levels in the lake shift by nine meters between dry and wet seasons. In a few scattered patches grow white-sand forests - campinarana - that hold species adapted to nutrient-poor sand in a basin otherwise known for clay. Within 23,500 square kilometers, Amanã compresses most of the major rainforest types the Amazon contains. From the air, you can see the transitions as subtle shifts in the green canopy, where a dense terra firma gives way to the feathered edge of igapó flooded forest.

The Amazonian manatee is the reserve's flagship endangered species. It is almost impossible to see in the murky water - a large gray shape that surfaces briefly for breath and vanishes. The Amazon river dolphin, the pink boto, fares better visually: it surfaces often and bows its long pink beak into the sun. The golden-backed uakari, a nervous short-tailed monkey with a red face and blond fur, lives in the seasonally flooded forest and moves only when trees offer a bridge. The harpy eagle perches on the high canopy - the most powerful raptor in the Americas, with talons long enough to snatch a sloth or a howler monkey. The arapaima, the giant pirarucu fish, surfaces in the lakes to gulp air. The undulated tinamou - a ground-nesting bird that looks like a plump partridge - follows the same migration rhythm as the manatees, tracking habitat between the dry and wet seasons.

The communities along Amanã Lake created the reserve, not the other way around. The Mamirauá Institute of Sustainable Development had spent years developing a new model of protection in the Mamirauá reserve just across the Japurá River, and the approach had worked: local fishing communities became partners in protecting manatees, arapaima, and the flooded forest they all depended on. When the possibility arose of extending the model, the residents of Amanã were ready. They already understood that the animals they hunted and the fish they caught could not survive unchecked extraction. As of 2011, 3,860 people in 648 households lived in 80 locations inside the reserve and another six on its edge. They farm, fish, hunt, and log - all within management plans that the communities themselves help design. The Mamirauá Institute administers the reserve. The people who live there manage it.

A sustainable development reserve is a distinctively Brazilian legal category, created in the 2000 National System of Conservation Units. Unlike a national park, it allows traditional residents to remain and to continue using the land - sustainably, monitored, and with the full participation of the community in the rules. Brazil has used this category extensively in the Amazon, where strict no-people national parks have often failed because the residents never left and the government never invested in enforcement. Amanã represents the strongest form of the model. Its residents vote on management plans. They catch arapaima under quotas they help set. They patrol for illegal loggers from outside the community. The reserve sits 650 kilometers west of Manaus, deep enough that reaching it requires days of boat travel along the Solimões and Japurá. That distance is its quiet protection. The people who live there are its active one.