Up the Rio Negro

The dark river that flows into Manaus [1] from the remote reaches of northwestern Amazonas [2] is known as the Rio Negro. Its somber hue is actually more dark reddish-brown than black, yet it is known as a “black” river due to the fact that its waters are filled with rotting vegetation from low-lying forests. The abundance of decaying organic matter results in a high level of acidity.

As a result, its waters don’t have the same fertilizing properties as “white” rivers such as the Solimões. A bonus is that the high acidity kills insect larvae, which results in a low instance of mosquito attacks.