Ilha das Cinzas (Island of Cinders) lies between two powerful branches of the Amazon, about six hours by boat from Macapá, the capital of Amapá state, Brazil. The nearest indigenous peoples are more than two days away, driven farther and farther south towards Belo Monte, where a huge, disputed hydroelectric dam is being built at the federal government's instigation.

But here human intervention is in tune with the environment. The forest is intact, the wooden houses stand on stilts, water is filtered and recycled, farming and fishing co-ordinated and controlled. Ilha das Cinzas seems a perfect example of well-integrated human activity.

The story began in the 1920s or 1930s when a handful of families came here to occupy various plots of land, but with no property rights. They were attracted by the potential for logging and the river's well-stocked waters. The community survived and slowly expanded; today there are about 100 families – roughly 350 residents in all.

Initially they derived their main livelihood from catching white prawns in the mangrove swamps. They supplemented their income selling palm hearts and acai berries, which they picked from the tops of palm trees. But by the mid-1990s the village was almost on its knees. The yield from the prawns was increasingly disappointing as reproduction was being hampered by fishing methods. Moreover it was difficult and time-consuming to harvest what the community did catch. To add to their woes, the price of palm hearts fell and the market for acai juice was relatively small. The villagers found out that a company had started operations not far from there, with plans for large-scale exploitation of the timber, threatening the ecosystem's fragile balance. Fortunately it soon folded.

Then the tide turned for the villagers. The Rio Earth Summit of 1992 was already recent history and the idea of sustainable development was beginning to take root. Non-governmental organisations were increasingly active in the field and the Brazilian authorities were keen to catch up. Jorgé Pinto, a member of Fase, an NGO specialising in environmental issues, landed on the island in 1996.

An agricultural engineer, Pinto studied the islanders' farming practice, compared crops and set up a scheme supported by Fase to carry out an expert appraisal. His ideas were well received and at the end of the first year the community decided to change the design of the macapis, the tubular cages used to catch prawn. The gap between the slats was enlarged to a centimetre, enabling baby prawns to slip through, thus improving stocks. Pinto also calculated that with about 120 per family, there were too many macapis. The villagers cut the number to 75 but the prawn yield grew and, with fewer cages to service, the villagers had more time to gather acai berries and harvest timber. The latter activity now complied with guidelines on the size of trees, and the space between them. "Our way of life became very organised," says Francisco, who was born on the island and has a distance-learning degree in financial management.

By the early 2000s acai juice had become a favourite drink for surfers at Ipanema and Malibu, providing the islanders with a basic income. On average each worker harvests two 60kg sacks of berries a day. They take them to market once or twice a week at Santana, the port of Macapá. A sack fetches about $40. "We make a good living," José Neide Maledos, one of the community leaders, admits. "Before 1997 our earnings were less than the minimum wage [$300]. Nowadays, adding up all our activities, we earn about 1,400 reals [$700] a month, more than twice as much."

Decisions are taken collectively and a non-profit organisation has been set up to handle relations with the authorities. In 2007, the islanders were granted the right to use the land they occupy. This ruling does not give them right of ownership but recognises their work and presence on the island. "The right to the land is vital for the people here," says Luiz Carlos Joels, the former head of the ministry in charge of forestry. "They need that right, if only to obtain loans or develop projects. The better established the right, the more residents feel responsible, improving crop yields and environmental protection."

Ilha das Cinzas has become an example for others to follow. In 2011 President Dilma Rousseff presented the community with a prize for the best social and technological innovation. On the nearby island of São João do Jaburu, a few people from Itatupa-Baquia nature reserve – federal government property – have tried to apply similar guidelines. But so far the experiment has not been convincing. The families live further apart and group decisions carry less weight. Which, according to Joels, demonstrates the need to "constantly maintain and encourage collective work".

This article originally appeared in Le Monde