Indigenous people living in the Amazon rainforest fear their survival is being threatened, as more and more trees are cut down to make way for farming and agriculture.
They say Brazil’s new president is now allowing deforestation in some of the 700 protected areas for indigenous groups within the Brazilian rainforest – which cover more than a tenth of Brazil’s entire land area.
Around 900,000 indigenous people live there – but that’s a tiny proportion of Brazil’s overall population.
The BBC’s Science editor David Shukman has been to see one group fearing for its future.