Qualla: Amazon Basin

Amazon Basin: Introduction

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit عبدالرحمن فراولو, CC0. The river used to run the wrong way. For tens of millions of years the waters of what is now the Amazon basin drained west, toward the Pacific, until the Andes rose and shut the door. Trapped water pooled into vast inland wetlands, then found a new exit to the east, and the continent's plumbing reversed. What resulted is a drainage basin of about seven million square kilometers, roughly 35.5 percent of South America, shared by Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname, Venezuela and French Guiana. Almost all of it drains, eventually, past the same handful of river towns.

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Image: عبدالرحمن فراولو | CC0

Amazon Basin: From Six Thousand Meters to Sea Level

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Public domain. The system begins as snowmelt and rain in the Peruvian Andes, gathering into the Maranon and the Apurimac, with the highest ground in the whole watershed standing at Yerupaja, 6,635 meters up. From there the water has about 6,400 kilometers to travel before it reaches the Atlanti...

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Image: Public domain

Amazon Basin: Dust From Another Desert

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Mário Oliveira - MTUR, Public domain. Rainforest soils are famously poor. Heat and rain strip nutrients out of the ground almost as fast as they arrive, which is why so much of the basin's living matter is held in the trees rather than the earth beneath them. Some of what replaces the losses comes from a very long wa...

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Image: Mário Oliveira - MTUR | Public domain

Amazon Basin: Counting the Uncountable

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit SOK, CC BY-SA 4.0. About 2,500 fish species are known from the basin, and researchers estimate more than a thousand more remain undescribed. Roughly 45 percent of the known species live nowhere else. Two orders dominate: characins account for some 43 percent of species, catfishes another 39 percent...

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Image: SOK | CC BY-SA 4.0

Amazon Basin: The Year Has Two Halves

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Julia Sumangil, CC BY-SA 4.0. Amazonians do not divide the year into hot and cold. They divide it into high water and low. When the rivers rise, they push out into the surrounding forest, submerging trunks to head height and turning woodland into a flooded canopy that fish swim through, feeding on fruit and s...

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Image: Julia Sumangil | CC BY-SA 4.0

Amazon Basin: Not an Empty Forest

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Limongi, Public domain. The old story held that the Amazon was too infertile to support large societies before Europeans arrived. Archaeology has taken that story apart. Patches of terra preta, dark anthropogenic soil built up over centuries of composting and low-temperature burning, turn up across the ...

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Image: Limongi | Public domain

Amazon Basin: The Ledger Tips

Thu, 16 Apr 2026 00:00:00 GMT

Photo credit Wellerson Santana, CC BY-SA 4.0. Amazon vegetation holds roughly 56.8 billion tonnes of carbon above ground, and the forest has long been counted as one of the planet's great carbon sinks. That accounting has begun to fail. Over the two decades to 2021, the Brazilian Amazon released about 13 percent more carbon ...

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Image: Wellerson Santana | CC BY-SA 4.0