Of Brazil's 2 million acres (850 million hectares) of land, about 1,400 acres (550 hectares) contain native forests, two-thirds of which are in the Amazon.
Sugarcane is not well suited for rain forest climates, Lacerda said, and the government is deliberately avoiding the expansion of sugarcane farms in the region.
But, he said, there is concern that higher-priced crops like sugarcane will displace soy and cattle farming in the Cerrado—driving those operations into the forests, which would have to be flattened to make way for the farms.
(Related photos: human encroachment in the Amazon.)
"This displacement effect is not hypothetical," Lacerda added. "São Paulo used to be one of the most important cattle regions in Brazil. Now sugarcane has replaced it and pushed cattle to other places in the Cerrado and Amazon."
A more direct worry for the Amazon is palm trees grown for their nuts' oil—another source of biological energy, Lacerda said.
"The potential to convert Amazon habitat in order to produce palm oil is huge," he said, noting that palm plantations have been among the biggest causes of the devastation of the rain forest in the Southeast Asian islands of Borneo and Sumatra.
(Related news: "Orangutan Habitat May Be Gone in 15 Years, UN Report Says" [February 7, 2007].)
"We want the government to have a plan for the displacement effect that sugarcane plantations will cause and for the arrival of palm cultivation in these areas."
Sugarcane industry officials, however, say deforestation concerns are overblown.
Carvalho Macedo of Brazil's National Sugarcane Agro-Industry Union says wildlands will not have to be plowed under, because Brazil has 200 million acres (809,000 hectares) of pasturelands available to absorb sugarcane growth.
"You don't need more than 5 percent of that land to reach production levels imagined for ten years from now," Macedo said.
Macedo said Brazil's current sugarcane production takes place on roughly 14.8 million acres (6 million hectares)—less than one percent of the country's total land dedicated to farming.
São Paulo state environment secretary Goldemberg writes in Science that "worldwide, some 49 million acres (20 million hectares) are used for growing sugarcane, mostly for sugar production.
"A simple calculation shows that expanding the Brazilian ethanol program by a factor of ten [in Brazil and other countries] would supply enough ethanol to replace 10 percent of the gasoline used in the world.
"This land area is a small fraction of the more than 1 billion hectares [2.5 billion acres] of primary crops already harvested on the planet."
In addition to deforestation issues, green groups have cited problems with localized air pollution around sugarcane fields, since farmers have traditionally burned the fields after canes are harvested.
Another concern is that wastewater from sugar mills pollute water supplies.
Antonio Luiz Lima de Queiroz, a specialist with São Paulo state's environmental agency, says the organization is addressing the problem.
"Our laws say that mills can never put water in the river that is worse than what the river has," he said.
Buchanan of Conservation International agrees that "there have been significant improvements in some sugar operations in São Paulo state.
"But there is room for broader adoption of these applications."
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