Manoel Jose Leite, a small-scale organic farmer, is set to pioneer low-carbon agriculture in Brazil's Amazon rainforest, which for decades has been destroyed by expanding agribusiness.

Finding the right balance between agriculture and environmental protection will be one of the major challenges on the agenda of the UN conference on sustainable development, which opens in Rio on Wednesday.

The issue is particularly pressing for leading grain exporter Brazil, 40 percent of whose huge territory is covered by the Amazon rainforest.

"We have learned a lot from the environment. We have some ideas of what reducing CO2 emissions means and we know that we must protect the Amazon," says Leite, who tills land in Brazil's northern Para state.

He arrived in this northern Brazilian city in 1974 when the then-military government encouraged people to settle the region by opening highways such as the Trans-Amazonian, which cuts through Anapu.

"There was only forest. The government wanted to settle the area. The more we cut trees, the better. If I had known then what I know now, it would have been different. I would have protected the forest," the 62-year-old told AFP as he stood by a spring on his land, which once was used for grazing.

Today he protects the environment with native tree reforesting, including planting Amazon rainforest trees such as cocoa, cupuacu and acai.

Leite is about to join a new project financed by Brazil and Norway that will help 2,600 families rehabilitate deforested areas with low-carbon farming, energy production and efficient use of resources.

"We want to show that you can have low carbon farming that reconciles forest preservation, food production and quality of life in the Amazon, where 25 million people live," said Lucimar Souza, of the non-governmental Amazon Environmental Research Institute (IPAM).

Similar projects are proliferating in the region.

"Between the 1992 Earth summit and the Rio+20, we went from unplanned production based on destruction of the forest to an awareness that this model is not sustainable," said Joao Batista, coordinator of the Live, Produce, Preserve Foundation.

Asked what was needed to make this remote region sustainable, Batista replied with a sigh: "a lot", underscoring the need for programs, technology and funding.

The reconversion coincides with a government commitment to combat the massive deforestation that has made Brazil one of the world's top greenhouse gas emitters.

The pace of deforestation peaked in 2004 at 27,000 square kilometers (10,000 square miles) a year.

But last December, the National Institute of Space Research (INPE) said deforestation had dropped to 6,238 square kilometers (2,408 square miles) per year, the lowest level since monitoring began in 1988.

The Brazilian Institute of Environment and Renewable Natural Resources (IBAMA) has taken action to crack down on 50 deforested zones spotted by satellites and to determine whether timber used in Anapu sawmills is legal.

Such action marks a drastic improvement from 2005, when local big landowners ordered the killing of US missionary Dorothy Stang, who was campaigning for sustainable forest projects in the face of large-scale illegal logging.

"With these sporadic actions we have significantly slowed down the deforestation" in recent years, said Eduardo Lameira, the head of a task force equipped with a helicopter and 4x4 vehicles to raid remote areas.

But challenges remain, and Brazil's dilemma was illustrated by the recent implementation of a new forest code, passed after a bruising congressional battle between the powerful agribusiness lobby and environmentalists.

The new code maintains a requirement to protect 80 percent of the forest in rural areas of the Amazon and 35 percent of the Sertao, the arid hinterland of northeastern Brazil.

But it eases restrictions for small landowners who face difficulties in recovering illegally cleared land.

In 1974, Brazil produced 20 million tons of grain, cereals and oilseeds. Today, it produces 160 million and has become a leading exporter of sugar cane, meat, soybean and timber at the cost of large-scale Amazon deforestation.

"Today we know that we cannot produce the way we did 40 years ago. We have enough deforested areas and the technology to use them for more efficient farming which preserves the environment," said Savio Mendoca, an adviser at the Brazilian Agricultural Research Corporation.

The issue will hotly debated at the Rio+20 conference, which will be attended by more 115 world leaders June 20-22, with the aim of charting a course toward a "green" economy that can balance economic growth with poverty eradication and environmental protection.