Hundreds of people have been killed while defending the environment and land rights around the world, international monitors said in a report released Tuesday, highlighting what they called a culture of impunity surrounding the deaths.

At least 908 people were killed in 35 countries from 2002 to 2013 during disputes over industrial logging, mining, and land rights – with Latin America and Asia-Pacific being particularly hard-hit – according to the study from Global Witness, a London-based nongovernmental organization that says it works to expose economic networks behind conflict, corruption and environmental destruction.

Only 10 people have ever been convicted over the hundreds of deaths, the report said.

The rate of such deaths has risen sharply – with an average of two activists killed each week – over the past four years as competition for the world’s natural resources has accelerated, Global Witness said in the report titled “Deadly Environment.”

“There can be few starker or more obvious symptoms of the global environmental crisis than a dramatic upturn in the killings of ordinary people defending rights to their land or environment,” said Oliver Courtney, a senior campaigner for Global Witness.

“This rapidly worsening problem is going largely unnoticed, and those responsible almost always get away with it,” Courtney said.

The report's release followed a dire warning by the U.N. Intergovernmental Panel on Climate Change, which said global warming is driving humanity toward unprecedented risk due to factors such as food and water insecurity. Global Witness said this puts environmental activists in more danger than ever before.

Land rights are central to the violence, as “companies and governments routinely strike secretive deals for large chunks of land and forests to grow cash crops,” the report said. When residents refuse to give up their land rights to mining operations and the timber trade, they are often forced from their homes, or worse, it said.

The study ranked Brazil as the most dangerous place to be an environmentalist, with at least 448 killings recorded.

One case that especially shocked the country and the global environmental movement involved the 2011 killings of environmentalists Jose Claudio Ribeira da Silva and his wife, Maria do Espirito Santo da Silva.

“The couple had denounced the encroachment of illegal loggers in the reserve and had previously received threats against their lives,” the report said.

Masked men gunned down the couple near a sustainable reserve where they had worked for decades producing nuts and natural oils. The killers tore off one of Jose Claudio’s ears as proof of his execution.