The uncontacted Ayoreo are forced to live on the run from the bulldozers constantly clearing their forest.
The study by the University of Maryland found that "Paraguay's Chaco woodlands ... are experiencing rapid deforestation in the development of cattle ranches. The result is the highest rate of deforestation in the world."
Dramatic satellite images (see right, second image) show the astonishing extent of forest destruction in the Chaco between 1990 and 2013 - and also that the area claimed by the Ayoreo (red outline) is one of the last remaining patches of forest left.
Forest essential to physical and cultural survival
Like many indigenous peoples around the world, the Indians depend on the forest for their survival and have protected it over thousands of years.
Paraguay's Environment Ministry recently caused outrage last year by granting Brazil-owned ranching companies Yaguarete Pora S.A. and Carlos Casado S.A. (a subsidiary of Spanish construction company Grupo San José) licenses to clear the Ayoreo's forest - despite it being within a UNESCO biosphere reserve.
The licenses were in violation of both national and international law and put the lives of the uncontacted Indians in extreme danger. Ayureo people told Survival:
"Our relatives came out of the forest in 2004 because they were under pressure from the ranchers, because they had no peace. If the bulldozers start to make a lot of noise, our uncontacted relatives will be forced to hide where there isn't any food and they will suffer.
"We want to continue using the forest, and for the ranchers to stop harassing our relatives who remain there."
Life on the run from bulldozers
The uncontacted Ayoreo are forced to live on the run from the bulldozers constantly clearing their forest. Any contact with the ranchers could kill them as they lack immunity to diseases brought in by outsiders.
In an urgent appeal to the UN's Special Rapporteur for indigenous peoples, the Ayoreo organization OPIT said that for the Ayoreo and their uncontacted relatives, "protecting the forest and their territories constitutes life itself.
"Yaguarete and Carlos Casado's ranching projects on the ancestral land of the Ayoreo-Totobiegosode would obliterate and devastate their forest system with all its natural resources."
Stephen Corry, Director of Survival International, said: "For how much longer will Paraguay boast two UNESCO biosphere reserves? With the world's highest rate of deforestation, the Chaco won't last forever: with it, the country's only uncontacted tribe will be obliterated.
"The government must stop Brazilian ranchers destroying its people's heritage before it's too late for the Chaco, and too late for the Ayoreo."