Fighting deforestation of the Amazon for cattle raising and farming is one of the great rallying cries of the world's conservationists.

And, while soybean growing's impact on the vast jungle has eased since a moratorium imposed in 2006, Brazil's huge soybean industry is still indirectly responsible for the felling of trees.

The mechanism goes like this: soybean growers take over land that has already been deforested, worked and worn out by cattle ranchers. The ranchers then move on to burn down fresh areas of Amazon.

Brazil is the world's second largest producer and exporter of soybean, after the United States.

Back in 2006, amid pressure from conservationists, the country's main soybean exporters stopped buying crops grown on deforested land.

This stemmed from a campaign launched by Greenpeace at the request of customers like Carrefour and McDonald's.

"This drastically reduced our industry's impact on the Amazon," said Bernardo Machado Pires, head of environmental affairs at the Brazilian Association of Vegetable Oil Industries (Abiove).

The moratorium is being observed by huge multinationals such as Bunge, Cargill or ADM, and involves 90 percent of Brazil's reported soybean exports, mainly to Europe and the United States.

"Soybean continues to spread in the Amazon but the moratorium has slowed its frantic expansion," said Michael Becker, a conservationist at WWF Brasil.

Areas that were deforested after 2006 and used to grow soybean increased 57 percent from 2011 to 2012, compared to more than 350 percent between 2008 and 2009.

Satellite images and pictures taken from aircraft by the National Institute of Space Research (INPE) show that such land now covers 18,400 hectares.

Persistent deforestation of the Amazon to grow soybean stems from the fact that some buyers, mainly Chinese, have not signed the moratorium.

Still, Brazil has imposed tough penalties on companies that produce soybeans on illegally cleared land or buy from it.

Indirect deforestation

"This agreement shows that consumers no longer tolerate deforestation of the Amazon, but it does not control the indirect impact of soybeans on the jungle," said Marcio Astrini, coordinator of Greenpeace Brazil's Amazon protection campaign.

He said growing is often done in places that had been used for cattle raising, which just goes elsewhere and ranchers burn down more trees.

Geographer Mariana Soares Domingues of the University of Sao Paulo, studies the process in the arboricultural state of Mato Grosso.

"Cattle ranchers burn down fresh jungle, plant grass from airplanes and then bring in cattle," she said.

"After a few years these pastures have been worn out, the cattle raising operations move on to deforest some place else and soybean growing takes over on these abandoned plots of land," she added.

"The soybean industry has an indirect responsibility," said Pires, of Abiove. "It buys land that has already been cleared, which is easier to plant, and the cattle raising moves to areas that are less expensive, in other words, the jungle. Thus are the dynamics of agriculture in these regions," he said.

INPE says that 2008 cattle grazed on 62 percent of deforested Amazon land.

Expanding into other territories

Soybean production in Brazil doubled from 2001 to 2012 and is spreading relentlessly into new areas.

"Direct pressure on the Amazon is easing but the expansion is coming at the expense of ecosystems like the Cerrado," said Becker of WWF, referring to a sprawling woodland savanna ecosystem in central Brazil.

The Cerrado accounted for more than 60 percent of the record soybean harvest posted in 2012-13. Brasil is now close to overtaking the United States as the world's top soybean producer this year.

Deforesting the Cerrado, and thus drying it out, would be hugely detrimental because it feeds huge rivers basins like Amazon and the Parana", said the geographer, Soares Domingues.

New forestry laws passed last year implicitly encourage the exploitation of the Cerrado: farmers can now grow on 65 percent of their land, compared to 50 percent before.

"Soybeans have a major impact on the Cerrado but our European customers worry about the Amazon and the native peoples. The market is not yet asking us to protect this ecosystem," said Pires, referring to the Cerrado.

Ecologists say Brazil, the world's fifth largest farmer producer, can increase production without felling a single tree.

"The country has 60 million hectares of former pasture or abandoned land. They could be turned into productive land and thus double the amount of farm land," said Astrini, of Greenpeace.

The soybean industry accounts for nearly 2 percent of Brazil's GDP and wields more and more influence on economic and political decision making.