On a recent visit to Rio de Janeiro, I was the lunch guest of Israel Klabin, a Brazilian industrialist who is also a leading environmentalist. (He is also a friend of mine.) Klabin has had a long career of public service, including stints as mayor of Rio de Janeiro and as an organizer of the 1992 Earth Summit. As president of Brazil’s Foundation for Sustainable Development, Klabin is now actively involved in preparations for the Rio + 20 Earth Summit that is scheduled for June, 2012. Klabin was upset about proposed changes to Brazil’s “Forest Code,” which the country’s Congress passed last month. (The vote was 410 to 63.) A consortium of agribusiness groups had lobbied heavily for the bill; so had Brazil’s Communist Party. Klabin characterized it as an environmental “catastrophe.”

The bill proposes, among other things, an official amnesty on all illegal forest destruction before 2008, a relaxation on logging restrictions, and giving Brazil’s individual states greater authority to set conservation goals. Klabin hoped some of the bill’s provisions could be amended in the Senate, where it will be debated next. Nonetheless, its approval is anticipated. The mere prospect of its approval seems, meanwhile, to have inspired a “go-for-it” attitude among farmers, ranchers, and loggers in the Amazon. In March and April, there was a five-hundred-per-cent increase in wilderness-burning and clear-cutting over the same period last year.

Brazil’s new President, Dilma Rousseff, a pro-development technocrat who took office on January 1st, will have the final word. So far, she has said she would oppose the bill’s amnesty provision, though others are potentially even more calamitous. (In an e-mail this week, Klabin wrote, “The overall potential of the new rules could range from 17 to 28 billion tons of emissions of CO 2 , depending on the scenarios. The impact would be tremendous.”)

To judge from current political trends, Brazil’s conservationists should be prepared for a bitter battle. On June 1st, just a week after the forest bill’s passage, Rousseff’s administration approved the Belo Monte Dam project. The three-year, seventeen-billion dollar project involves the construction of a mega-dam on the Xingu River, a major tributary of the Amazon and one of South America’s great wild rivers. When it is completed, in 2015, Belo Monte will be the world’s third largest dam, flooding an estimated hundred and twenty thousand acres of rainforest in the Amazonian state of Pará, including part of the traditional homeland of the Kayapo Indians. The dam’s construction has been held up for decades due to the opposition of environmentalists, the Kayapo themselves, and other indigenous groups. Belo Monte’s advocates say a mere twenty thousand people will be affected and that they will be financially compensated. Belo Monte, they say, is necessary to safeguard Brazil’s “national sovereignty” by providing enough energy to meet the demands of its booming economy, which grew last year at the rate of 7.5 per cent.

With development fever spreading in Brazil, it seems to be open season not only on the Amazon’s forests but also on those people who try to protect them. On May 24th, the day the bill was being debated, news broke that a pair of assassins on a motorbike had ambushed Jose Claudio Ribeiro da Silva, an environmental activist, and his wife, Maria, and killed them. In the trademark style of contracted executions, the killers gave Ze Claudio, as he was known, and his wife coup de grace bullets to their heads and then removed an ear from each of them. Ze Claudio was a charismatic and outspoken opponent of land-grabbing ranchers and charcoal burners; last November, in a speech he made at a TEDx conference held in Manaus, he spoke of receiving death threats. When a legislator announced the news of the murders in Congress and called for an investigation, a round of booing erupted from the agribusiness-backed “ruralistas.”

Three days later, in Rondonia, another front-line Amazonian state, Adelino Ramos, another prominent environmental activist, was shot dead in front of his wife and children. The next day, a few miles from where Ze Claudio and his wife were murdered, a young man named Eremilton Pereira dos Santos was gunned down, execution-style. His relatives said that he may have witnessed Ze Claudio’s killing. On June 9th, in the latest such incident, another peasant activist was murdered in Pará.

“It is all part of a sadly familiar pattern,” Scott Wallace, author of a forthcoming book, “The Unconquered,” about the Amazon’s last uncontacted tribes, wrote to me in an e-mail:

The murder is in the same vein as many of the others that have taken place in the Amazon, and in the state of Pará in particular, over the past twenty years. You have bald-faced criminal types muscling into public land, cutting the trees, clearing the forest as though it’s theirs…. If they are not the local mayors, councilmen, or state legislators, they’re close friends with them and contribute generously to their electoral campaigns…. The crimes are rarely prosecuted. That’s why so much of rainforest devastation proceeds hand in hand with lawlessness.

In 2005, the Ohio-born nun Dorothy Stang, a champion of rainforest conservation, was also murdered in Pará, a contract hit ordered by local ranchers and loggers. Brazil’s Pastoral Land Commission has announced that Ze Claudio, his wife, and Adelino Ramos had all been on its list of activists who were thought to be in danger. It said that an additional hundred and twenty-five activists were regarded as potential targets for assassination. A few days ago, after a series of high-level emergency ministerial meetings, the government sent a unit of sixty élite police officers to Pará to protect some of the threatened activists. But Pará is known in Brazil as the “state without law,” for its lack of judicial follow-through on criminal offenses. Of the hundreds of homicides registered in the state, very few suspects have ever been apprehended.

The Brazilian journalist Felipe Milanez, who was a friend of Ze Claudio and his wife Maria, and who has been following up the police inquiry into their murders, wrote me to say that a local rancher is a focus of a police investigation. “We hope they are going to do their job,” he said. “But we don’t know if they will yet.”

Another Brazilian friend of mine, Jose Junior, a founder of a favela-based N.G.O., Afro-Reggae, was recently in Pará. By coincidence, he was to have interviewed Ze Claudio the day of his assassination, and he attended the wake of Eremilton Pereira dos Santos a few days later. Junior, who grew up in one of Rio’s toughest favelas, wrote, “Never in my life have I been to a wake like that, where the mourners were too afraid to cry.”

Still image from Jose Claudio Ribeiro da Silva’s TEDx talk.