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Published: 2000-03-20

Former ECHO intern Dale Haskell brought this interesting example of indigenous knowledge to our attention. It is adapted from the website Space Daily.

“For centuries, Andean farmers in Peru and Bolivia have monitored the brightness of the Pleiades stars to determine when to plant potato crops for optimal rainfall.” [Ed: The Pleiades refers to a group of stars that appear to make a small dipper. They are actually part of the constellation Taurus.]

“Now scientists have validated the farmers’ weather forecasting methods. They can demonstrate that atmospheric fluctuations–in particular El Niño–explain the variability in star brightness. El Niño is a weather phenomenon that occurs when tradewinds that normally blow westward across the tropical Pacific Ocean relax, and the warm water in the western Pacific drifts back toward Peru and up the coasts of North and South America, prompting atmospheric changes.

"In a letter to the journal Nature, UC Davis environmental scientists …describe the reasons for the changing brightness using satellite data on cloud amounts and water vapor. Using the data, the scientists link poor visibility of the Pleiades in June, reduced rainfall during the growing season and lower harvests to El Niño warm events.

"When the Pleiades cluster is particularly bright or when it appears to be large, Andean villagers anticipate earlier and more abundant rains and larger harvests, while the opposite is linked with less clear skies. If poor rains are predicted, the farmers postpone potato planting.

"Using the satellite data, the researchers found that thin clouds above the earth’s surface occur more frequently in El Niño years than in La Niña years. These additional clouds in El Niño years block some of the light from the Pleiades. This shift is sufficient to visibly reduce the apparent brightness of the Pleiades in El Niño years.

"In particular, dimmer stars warn observers of a later start to the rainy season and reductions in overall rainfall and harvests. Armed with this forecast, indigenous farmers alter their cropping strategy by planting at a later date.”

Cite as:

ECHO Staff 2000. Farming by the Stars in the Andes. ECHO Development Notes no. 67