The Rio Juruá area, which makes up about a third of the small northwestern Brazilian state of Acre, straddling the Peruvian border has been discovered to have a higher level of biodiversity than any other comparable region on earth, including all other areas in the Amazon rainforests. Researchers from the University of Chicago and Tulane University in the US and from the Brazilian city of Belem’s main museum believe that 8,000 mainly indigenous inhabitants, spread throughout the area in isolated, small settlements, which have been there for generations, are a principal cause of such great biodiversity.

The researchers say that inhabitants, with their small-scale impact on the environment through hunting and movement, including building of paths and tracks, have helped break the dominance of certain species, allowing others to flourish. “Long term settlement has altered at least 10% of the present composition of the rainforest,” said Tulane’s researcher William Balee, adding that when population grows at an uncontrolled rate, it has the reverse effect on biodiversity, with a 20% loss of species. Another factor which has been cited for the biodiversity is the area’s cooler and more humid weather conditions than are found elsewhere in the Amazon.

Researchers have, until now, discovered the following number of species in the Rio Juruá basin, but say that there could be many more:

  • 616 species of birds, including two previously unknown to science;
  • 16 species of monkey;
  • 140 frog species;
  • 50 reptile species;
  • 1,620 butterfly species, including the biggest in the world, with a 30cm wing span;
  • 300 spider species;
  • 64 varieties of bee; and
  • 103 bat species, including one with a one metre wing span, the largest in the Americas.

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