Ecologists sounded the alarm. The Amazon rainforest is disappearing at the fastest rate in nearly a decade. But the outcry left many Brazilians suspicious.
They say the protesters don't really care about saving the world's largest wilderness -- they want to steal it from Brazil.
Sprawling over 4.1 million km2, the Amazon covers nearly 60 percent of Brazil. Largely unexplored, it contains one-fifth of the world's fresh water, oil, diamonds, gold and untold other mineral and biological riches.
Last year, the Brazilian Amazon lost an area of 26,130km2 of rainforest, an area slightly smaller than Belgium. Environmentalists estimate as much as 20 percent of the jungle has already been cut down by ranchers, loggers, farmers and developers.
But the idea that the Amazon is important for the world's climate, its biodiversity and a global heritage is seen as a smoke screen -- the rainforest belongs to Brazil, and anyone who says differently has ulterior motives.
"I am also convinced that the international attention to the recent news of deforestation has much more to do with the internationalization of the Amazon than with preservation of the rainforest," General Claudio Barbosa de Figueiredo, head of the Brazilian military's Amazon Military Command, said at a seminar entitled, "The Amazon Brazilians Don't Know."
To outsiders, fear of an invasion by a more powerful country such as the US seems farfetched. Indeed, in other countries that have Amazon rainforest within their borders -- Colombia, Venezuela, Peru, Ecuador, Suriname and French and British Guyana -- people tend to fear more that Brazil will try to seize the entire rainforest.
But in Brazil, a recent poll sponsored by Renctas, a group that combats animal trafficking, found that 75 percent of the people believe their country runs a real risk of being invaded by a foreign power that covets the country's vast natural riches.
"The strategic axis of confrontation has shifted from East-West to North-South," Figueiredo said. "In other words, the rich countries of the North are confronting the countries that want to develop in the South to impede this in every possible way."
Figueiredo explained that Brazil's generals have developed a strategy of "resistance" to deter a superior military power by employing guerrilla tactics in the Amazon.
"There are military planners seriously engaged in this policy of resistance. When I ask them who the superior power might be, they say `the United States' or `the G-8,'" said Celso Castro, a history professor at the Getulio Vargas Foundation, at a seminar. "Most of my students believe foreign invasion is a real threat, too."
In recent years, the government has spent US$1.4 billion on a sophisticated radar system to monitor air traffic over the Amazon region and has bulked up troop strength along its porous jungle borders.
The conspiracy theorists say groups defending the environment or Indian rights are merely fronts for interests to steal the region's riches and undermine national sovereignty. Foreign military aircraft cruising in or near Brazilian airspace are said to be attempting to map the region's vast mineral wealth.
Many Brazilians believe that grade school children in the US are taught the Amazon is part of an "international reserve."
"That's what people are raised to believe here. Most people believe in one form or another that foreigners want to steal the rainforest," said Philip Fearnside, a research professor for 29 years at the National Institute for Research of the Amazon, in the jungle city of Manaus.