FILE - In this Sept. 15, 2009 file photo, a deforested area is seen near Novo Progresso, in Brazil's northern state of Para. The Brazilian Amazon is arguably the world's biggest natural defense against global warming, acting as a "sink," or absorber, of carbon dioxide. Brazilian legislators are pushing to resume debate Tuesday, May 24, 2011 on changes to an environmental law that watchdog groups warn will speed destruction of the Amazon rain forest. (AP Photo/Andre Penner, file)
They watched as their beloved Amazon rain forest fell around them. Instead of staying quiet, as so many people in the lawless region do, environmentalist leader Jose Claudio Ribeiro da Silva and his wife, Maria, fought back.
They reported illegal loggers to police and federal prosecutors. They confronted powerful interests that destroy the forest for the quick economic gains to be made from selling timber, or from clearing land to raise cattle or soybeans.
This week, like so many Amazon activists before them, the Silvas were gunned down.
They were killed Tuesday near the sustainable reserve on government-ceded land were they led about 300 families working the forest in the Amazon state of Para, one of Brazil's most violent and lawless. Federal police said Friday that they were investigating, but had not made any arrests.
Authorities say there is little doubt the couple were assassinated for their work. They faced numerous death threats, nothing was stolen off their bodies and Silva's ear was cut off, likely as proof that he was dead.
Two more names were tacked onto an ever-growing list of more than 1,150 rural activists who have been slain in land conflicts across Brazil in the past 20 years, murders mostly carried out by gunmen hired by loggers, ranchers and farmers to silence those who protest illegal cutting in the forest.
So many die because so few face punishment.
Of all those killings, fewer than 100 cases have gone to court. About 80 hired gunmen have been convicted. Only 15 or so of the people who have ordered killings faced charges. And just one of them one is known to be in prison.
Impunity rules among the 23 million people spread across the vast Amazon because Brazil's judicial system is weak and corruption among local officials is endemic, activists and federal prosecutors say.
It's a big hurdle for the Brazilian government's efforts to preserve a rain forest the size of the U.S. west of the Mississippi River. More than 20 percent of the forest already has been cut down. On the same day that Silva and his wife were slain, Brazil's lower house of Congress passed a bill that would weaken the nation's cornerstone environmental laws, changes that environmentalists fear will lead to more destruction if the measure passes the Senate.
Those on the ground in the Amazon say that until the violence stops, the forest will keep falling, because most people in a position to denounce illegal clearing keep quiet out of fear.
Threats against anyone who stands in the way of those who want to clear the Amazon are so routine, the Catholic Land Pastoral watchdog group keeps a running list of activists whose lives have been threatened.
Silva, who publicly predicted his own death just six months ago, was on the list, along with 124 other environmentalists.
"The impunity for killing us is getting worse by the day," said Leonora Brunetto, a 65-year-old Roman Catholic nun and activist in the Amazon who is on the death-threat list. "We can cry out, denounce what is happening to the forest, but it continues. I see no end to it."
Activists like Brunetto can be guarded by police, if they request it and if the threats against them are deemed real. She briefly took advantage of the protection years ago, but realized she was safer among the poor, small-scale farmers she counsels.
"You have no way of knowing if the policeman who is guarding you today will be bought off tomorrow by the same forces that hire the gunmen who kill Amazon defenders," she said.
Brunetto, like many activists, leads a cloak and dagger life, rarely sleeping in the same place on consecutive nights. She travels furtively, frequently changing from car to truck to car, handed off like a sacred baton from one poor farmer to the next, visiting jungle settlements across Mato Grosso and Para states.
During her decades of work, at least 15 of her close friends have been murdered in the Amazon, Brunetto said.
And, she said, there will be no security until the underlying problem of land titles in the Amazon is settled. The lack of clear ownership in the region drives its violent conflicts -- and much of the deforestation.
A report last year from the environmental watchdog group Imazon said that on average, proper titles are held for only 4 percent of the land in the states that comprise Brazil's Amazon, excluding federally protected zones. Nearly 45 percent of the Amazon lies within protected zones, but even those are encroached upon illegally.
The result is that loggers, for instance, can simply claim huge chunks of land with the power of a gun and authorities have little way of knowing who is responsible for the destruction left behind by clear-cutting of trees.
Two years ago the government started an aggressive campaign to register landowners in the Amazon. In its first year officials registered more than 74,000 plots totaling 20.7 million acres (8.4 million hectares), an area the size of Panama. But that still leaves more than 50 percent of the land unregistered.
While much of the Amazon remains up for grabs, those backed by guns will continue to kill activists who stand in their way, said Edson Souza, a federal prosecutor in Para state.
Souza last year put in prison rancher Vitalmiro Moura, one of the men found guilty of ordering the 2005 slaying of 73-year-old U.S. nun Dorothy Stang. Moura is the only person known to be in jail for ordering an activist killed.
Another rancher convicted of ordering the killing of Stang, who also was shot down in Para state, is free pending an appeal.
"The killing of Silva and his wife was what we call an 'announced death,"' Souza said. "You could see it coming. A couple fighting against illegal logging in this part of the Amazon are targets, sadly. There is too much money involved."
Silva and his wife pioneered the creation of the 54,300-acre (22,000-hectare) sustainable reserve where they were slain. The reserve specializes in the sustainable harvesting of Brazil nuts, which come from huge jungle trees.
Silva filed numerous complaints with local police and prosecutors about loggers illegally entering the reserve and chopping down trees for lucrative lumber.
He and his wife received many death threats, but they pushed on with the project.
Silva's sister Claudelice dos Santos said she has handed over to police a list of names of people she suspects killed the couple.
"We will march in protest against the killings and for the environmental cause," she told a local newspaper. "We are certain they were killed because of their environmental work."
While the killings are meant to spread fear among the activists who work in the Amazon, the nun Brunetto said each death, while unwelcome, strengthens her convictions.
"I'll keep fighting. It won't do to give up," she said. "These events wake more people up, they make people more conscious of what is at stake here."
The Associated Press contributed to this report.