[11] List of the major tributaries of the Içá–Putumayo (from the mouth upwards):[12] In the late 19th century, the Içá was navigated by the French explorer Jules Crevaux (1847–1882).

[13] Arana's production network mainly relied on the labor of enslaved indigenous people, who suffered from widespread human rights abuses.

[14] In response to Hardenburg's exposé, the British government sent the consul Roger Casement (who had previously publicized Belgian atrocities in the rubber business of the Congo Free State) to investigate the matter; between 1910 and 1911, Casement subsequently wrote a series of condemnatory reports criticizing the atrocities of the PAC, for which he received a knighthood.

[15] Casement's reports later formed much of the basis for the 1987 book Shamanism, Colonialism, and the Wild Man by the anthropologist Michael Taussig, which analyzed how the acts of terror committed by British capitalists along the Putumayo River in Colombia had created a distinct "space of death."

[16] In November 2019, scientists from the Field Museum worked with partners from Colombia and Peru to perform a three-week "rapid inventory" of almost 7 million acres around the Putumayo, one of the few Amazonian rivers that remains undammed, documenting 1,706 species.