What Really Keeps the Amazon Alive?

The biggest rainforest on Earth grows mostly on soil starved of nutrients. So what keeps it alive? The answer runs through a mountain range, an ocean, a desert and the trees themselves: a river that once flowed west until the Andes rose, mud that only some rivers carry, a forest that sends almost as much water back into the sky as the river carries past Óbidos, and phosphorus blown in from a dried-up lake in the Sahara. Chapters 0:00 What really keeps the Amazon alive? 0:24 The river that turned around 1:33 Mud from the mountains 3:16 The forest that makes its own rain 4:55 Fertilizer from the Sahara 7:15 Pull out one part Sources River history: Figueiredo et al. 2009, Geology 37:619; Hoorn et al. 2017, Global and Planetary Change 153:51; BBC News 2006 (Mapes & Coleman, zircon dating); Wesselingh et al. 2006 via Wikipedia (Pebas Formation); Salas-Gismondi et al. 2015, Proc. R. Soc. B 282:20142490 Flow and mud: Wikipedia, Amazon River and List of rivers by discharge; Amazon Waters (Wildlife Conservation Society), after Goulding et al. 2003, Smithsonian Atlas of the Amazon; McClain & Naiman 2008, BioScience 58:325; NASA Earth Observatory (Meeting of the Waters, 2012) The forest's own rain: Baker et al. 2021, Hydrology and Earth System Sciences 25:2279; GRDC station Óbidos; Staal et al. 2018, Nature Climate Change 8:539; Wright et al. 2017, PNAS 114:8481 Soil and phosphorus: Quesada et al. 2010, Biogeosciences 7:1515; Cunha et al. 2022, Nature 608:558 Dust and smoke: Yu et al. 2015, Geophysical Research Letters 42:1984 and NASA (22 Feb 2015); Koren et al. 2006, Environ. Res. Lett. 1:014005; Bristow, Drake & Armitage 2009, Geomorphology 105:50; Barkley et al. 2019, PNAS 116:16216 Tipping point: Lovejoy & Nobre 2018 and 2019, Science Advances; Flores et al. 2024, Nature 626:555 Images: NASA (MODIS, Earth Observatory, ISS, CALIPSO, zircons), Gordon T. Taylor / NOAA Photo Library (diatoms), La Condamine's map of the Amazon, 1744 (all public domain); Carlos Nobre photo: MCTI Brazil, CC BY 2.0; maps: NASA Blue Marble, Natural Earth, HydroBASINS (WWF), AWS Terrain Tiles (SRTM, GMTED, ETOPO1) Notes: cross-sections, the tree, the bathtub and the timeline are schematic and labelled on screen; the dust, smoke and moisture particles show directions, not amounts; the mud is drawn only on the Andes-fed rivers. The CALIPSO numbers (182, 132 and about 28 million tonnes) are separate yearly averages for 2007-2013, so they do not add up. The tipping-point range is a proposal, and the 10-47% figure is a 2024 estimate for 2050. #Amazon #Geography #Rainforest