It protects an area of contact between Amazon rainforest in the north and Cerrado semi-deciduous forest in the south.

On 20 April 2005 the state legislative assembly reduced the area to 102,000 hectares (250,000 acres).

[4] 38% of the ESEC is covered by pioneer formations and 62% by mature forest, including open submontane Amazon rainforest in the north, seasonal semi-deciduous Cerrado forest in the south and the contact zone between these biomes.

[3] The unit is threatened by illegal logging, land clearance for agriculture, indiscriminate hunting and fires.

[5] A 2014 study of ten protected areas in Mato Grosso, Rondônia and Pará whose size had been reduced since creation, including the Rio Ronuro Ecological Station, concluded that the reduction in area had caused the deforestation process to accelerate.