Of the indigenous groups that were known to exist in 1900, one-third of these groups are now extinct.
In the late 15th century, the total number of indigenous peoples in the Amazon was calculated to be over 6 million.
Indigenous peoples inhabit a large portion of the Amazon rainforest and their traditional and cultural beliefs have existed for centuries, providing storage for an immense amount of knowledge about the tropical Amazon.
Within Brazil, the indigenous population is estimated to be 310,000. Around 280,000 of these individuals reside within areas specifically designated as preserves. In the late 15th century, the total number of indigenous peoples in the Amazon was calculated to be over 6 million. There are 160 different individual societies within the borders of the Brazilian Amazon that speak 195 different languages.  Despite their traditional settlement of the rainforests within Brazil, their legal and constitutional rights only provide them with about 20 percent of the land within the Brazilian Amazon. In a study by a consortium of US and Brazilian researchers, deforestation rates within indigenous protected areas were inhibited compared to unprotected lands, signifying that indigenous lands could serve as important repositories for threatened species and could be used in conjunction with conservation efforts. 
While not as large as Brazil’s, the indigenous communities of other countries containing tropical rainforests (Bolivia, Ecuador, Peru, Colombia, the Guyanas, Venezuela, and Suriname) all consist of populations with deep and detailed knowledge of the rainforest. Much of this knowledge regards the usage of rainforest species for traditional medicines. The Tisame people of the Bolivian Amazon are typical of this pattern; about 20% of all plants consumed are for medicinal purposes and the Tisame use 47 different local species.  Tropical Botanists often rely on local knowledge to classify and identify native plant species, linking cultural and traditional medicinal uses of Amazon species to the worlds of science and conservation today.
The non-indigenous population of the Amazon is exploding. From the 1960’s until the late 1990’s, this number grew from 2 million to around 20 million.  As the development of infrastructure projects continues within the Amazon rainforest, migration of non-traditional peoples will increase and come into conflict with traditional forest-dwellers, particularly those not protected by reserves. Of the indigenous groups that were known to exist in 1900, one-third of these groups are now extinct.  With the loss of these populations follows devastating losses of cultural diversity, treasure troves of anthropological information, and partners for the future of conservation in the Amazon. 
Despite the moral, historical, and cultural obligations to maintain indigenous lands in the control of indigenous peoples, these cultures face a variety of threats to their existence from the outside world. First contact between isolated indigenous cultures brings with it the mortality of from one-third to one-half the population within the first several years.  While most countries typically have laws prohibiting contact with isolated populations to avoid contact-related death, some countries waive this restriction for developmental purposes. Peru is a notable example of when the ban on contact can be lifted, with a law passed in 2006 and a presidential decree in 2007, both which benefit development over cultural preservation. It comes as no surprise, as nearly 72 percent of the Amazon in Peru are available for oil and natural gas exploration.  Clearly, attention must be paid to this developing issue for the maintenance of cultural diversity, the health and well-being of indigenous people in the Amazon, and the health of the Amazon as a functioning ecosystem.
Written by Dr. Dave Lutz for the Amazon Aid Foundation
7. Napolitano DA, Ryan AS (2007) The dilemma of contact: voluntary isolation and the impacts of gas exploitation on health and rights in the Kugapakori Nahua Reserve, Peruvian Amazon. Environmental Research Letters, 2, 1-12.