Indiscriminate logging and deforestation to make way for cattle made the south-eastern portion of this state the most devastated area of the Amazon.
The availability of cheap land in the Amazon meant farmers tended to abandon areas after a few years of production.
"It's cheaper to open up the forest for fresh land than to recover pastures," says Paulo Barreto, senior researcher at a non-governmental organisation, the Amazon Institute for Mankind and the Environment (Imazon).
"This is the mindset that we need urgently to change."
One major problem is that the Amazon soil is actually sandy and rather poor. The vegetation is lush only because it feeds itself with all the organic matter provided by dead plants and animals.
Once this cycle is broken by agriculture, the soil turns to sand in a few years and farmers burn another bit of forest.
This is the technique Indians used for centuries in the jungle, but not on the industrial scale of today.
"The change is slow, but it's coming," says farmer Mauro Lucio Costa.
Mauro Lucio Costa says more farmers are trying to practice sustainability
Still an exception in the Amazon, his 4,500 hectare (11,000 acre) farm boasts productivity some four times higher than the Amazon average, while retaining 80% of the native forest on the land.
Mr Costa says that when he started to develop sustainable practices in his farm - such as reforesting and researching better varieties of pasture - other farmers said he was "crazy" for investing in technology in a sector dominated by intensive farming.
"But that was almost 10 years ago," he says.
"Fortunately today I see more and more farmers adhering to these principles, but it will take some time for this to be felt in practical terms."
Farmers say they desperately need credit if they are to modernise their production processes.
The situation is even more dramatic among the small landowners who usually do not have any capital for investment.
"Three years ago the banks said we should invest in producing black pepper because there was some problem with the plantations in Asia and there would be a huge increase in demand," says Marusan Moreira.
"I took a loan and planted a lot of pepper but then the price dropped and the bank did not want to give me more money to hold on."
Marusan Moreira tried planting pepper, but prices dropped
Mr Moreira says he had to sell the few cattle he owned to stick with the pepper, trusting that the prices would go up again.
"But they didn't and now I have nothing. I had to stop working because the more I produced, the more I lost," he said.
Now Mr Moreira needs to register his land under a new government scheme to grant ownership rights to people who have occupied land in the Amazon to get access to credit facilities.
However, environmentalists fear that giving more money without the proper safeguards could lead to more destruction of the jungle.
Patricia Baiao, Amazon programme director for Conservation International, an NGO, says that the region needs "a customised model" of economic development.
"Sustainable extraction of wood and collection of forest goods for cosmetics and pharmaceutical industries are the kind of activities that could get incentives," she says.
A group of carpenters in the city of Rondon do Para - listed by the Brazilian government among the 15 most deforested areas in the Amazon - have set such an example, using leftovers from the region's saw mills for their furniture.
Usually wood buyers are very strict about what they want from the mills.
Any little imperfection in a piece of wood - a spot or a vein in another colour - is enough for it to be discarded for use as charcoal.
Gilberto Fernandes makes furniture from rejected cuts of wood
"I found out that thousands of these little pieces of wood were discarded by a big company that buys this material to produce for cutlery handles," says carpenter Gilberto Fernandes.
Now he uses them to produce furniture in his backyard carpentry but bureaucracy is a problem.
"I have not yet managed to properly register my company with the government to be able to send my furniture to other states. This is what would allow me to really develop my business."
Quite a few farmers who have devastated the jungle for decades - be it for wood or for opening up new spaces - are now trying to come up with sustainable activities.
John Weaver Davis Jr on how his father spotted a market for wood
One is American John Weaver Davis Junior, who came with his missionary father from Texas in the early 1960s to establish a farm and agricultural mission in Brazil.
Mr Davis's father, who was killed in a land dispute a few years after arriving in Brazil, sought out markets for Brazilian hardwood in Europe and the US.
After decades of wood extraction, less than half of the property - originally 100,000 hectares (250,000 acres) is still covered by jungle.
"We don't regret anything because that is what we had to do to sustain our family and it was a viable activity in its time," says Mr Davis.
Now he says it is time to focus on the forest and is trying to get public financing to grow the fibre rich curaua plant.
"This is a traditional plant whose fibres the Indians have always used for hammocks, clothes and bow strings," he says.
"Now we know it can replace fibreglass in many industrial applications. And the most important thing is that this is a plant that asks for a forest because in the shade it grows much better."
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