The reserve is in the
Guiana Shield, with rocks that date to over 2 billion years ago. The terrain is very rugged, with hills and plateaus dissected by streams. Soil is mostly
oxisol, with low natural fertility and low to medium vulnerability to erosion. In the Jari River Basin as a whole, which includes the reserve, deforestation is just 0.48%. Vegetation in the reserve is mainly terra firme forest, with small patches of other types of vegetation. There is some flooded forest in narrow strips along watercourses. Quick surveys of flora have identified 398 plant species in 78 families. Emergent trees of around in height have been observed. Some tree trunks have diameters over . There is great diversity of fauna, including rare and endangered such as the
giant anteater,
giant otter and
jaguar. 41 mammal species have been recorded from 36 genera, including 8 primates. Of small mammals the most common are
Proechimys spiny rat species and the
brown four-eyed opossum (
Metachirus nudicaudatus). 41 species of bats have been found; the
flat-faced fruit-eating bat (
Artibeus planirostris) is the most common. At least 164 species of fish are present, and there are almost certainly many more. A total of 376 bird species in 61 families have been listed. The bird population in the north of the reserve seems to have been affected by
garimpo mining. 54 species of amphibians have been recorded and 67 of reptiles. Two of the amphibians and one lizard were previously unknown. The threatened poisonous frog
Atelopus spumarius has been reported. Potential threats identified by a technical mission of the Guiana Shield Facility in April 2008 included logging, mining, road building, human settlements and agricultural development. Illegal small-scale mining, mostly in the northeast, causes water pollution with mercury, a major problem. Mining is mainly concentrated along the rivers and near the
BR-210 highway to the northeast of the reserve. As of 2013 the harvest of Brazil nuts was declining, perhaps due to poor regeneration and over-harvesting by the growing human population. The hydroelectric plant at Santo Antônio do Cachoeira which was completed in 2014 will cause pressures on the environment. ==Economy==