The Amazon basin was once a westward-flowing river system before the Andes mountains formed.

Countries & Cities · Published 29 September 2026 Swipe more like this →

In short: Spanning 7 million square kilometers, the Amazon basin is the world's most biodiverse region. While it is famous for its dense rainforest and vast river network, this landscape is a dynamic product of geological shifts, Saharan dust, and a complex web of indigenous cultures and migratory fish populations.

The Amazon basin covers about 35.5 percent of South America, stretching across eight countries and French Guiana. Geologically, the system once drained toward the Pacific Ocean, but the rise of the Andes Mountains forced a reversal, directing the flow eastward into the Atlantic. Today, the basin is defined by its extreme biodiversity, supported by ten million tonnes of Saharan dust that crosses the Atlantic annually to fertilize the lush flora.

Life in the basin is defined by the rhythm of the water. During the wet season, rivers flood the surrounding forests, creating unique habitats for thousands of species. The basin is home to over 2,500 described fish species—more than any other river system on Earth—with roughly 45 percent being endemic. These fish have adapted to diverse conditions, from dark, deep river channels to land-based survival strategies, such as the splash tetra, which lays eggs on plants above the water.

Human presence in the basin is sparse, with most of the 1.5 million inhabitants concentrated in cities like Manaus and Belém. Beyond these urban centers, roughly 400 tribal groups maintain distinct cultures and languages, though many are critically endangered. The economy relies heavily on fishing, which provides over 200,000 jobs. However, overharvesting of migratory species and the expansion of cattle ranches and soybean fields pose significant threats to the basin's delicate ecological balance.

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