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INSTAAR Seminar: Sodium biogeochemistry, the hunger for salt, and Amazonian biogeography

Monday, April 10, 2017, 12:10PM - 1:10PM


Robert F. Stallard



SEEC S228 (Sievers room)

4001 Discovery Drive, Boulder, CO

Sodium, in natural waters, comes from sea salt blown inland, desert saline dusts, and bedrock weathering. The extremely mobile sodium ion is typically not retained on soil clays, and unlike other ions needed by animals, sodium is generally not accumulated by plants. Throughout human history, salt (sodium chloride) has had an enormous role in shaping societies primarily through it being an essential nutrient. For example, in English, the word "salary" is derived from the name of an allowance given to Roman soldiers to buy salt. Major historical syntheses of the role of salt in shaping cultures have been published for much of the world; however for South America, such information is in notably short supply.

My own work over the last 40 years, much of it over the last 12, shows that the sodium deficit in western Amazonia is far deeper than previously assumed and that localized abundant sodium, in water and sediments, is typically associated with certain geologic formations and with faults. The sodium cation is often a limiting nutrient for animals and humans across Amazonia, and animal behavior and human activities for surrounding regions is, in part, arrayed about these sodium occurrences. While undertaking these biogeochemical studies, I searched for and found, with the aid of a Swedish colleague, an important ethnographic manuscript synthesizing the human geography of salt for South America that had been lost for 50 years due to the untimely death of its author. This manuscript and recent research helps place the biogeochemical findings into a human context.


Free and open to the public.