It’s only in the last 20 years that scientists have been able to forecast El Nino, the global weather phenomenon.
But it turns out that people in the Andes mountains of South America have long been using El Nino to plan their
farming calendar. I’m Jim Metzner and this is the Pulse of the Planet, presented by DuPont. For centuries,
villagers in Peru and Bolivia have gone up to a mountaintop on a night in June, close to the time of their winter
solstice. They look at the constellation called the Pleiades, believing that its visibility predicts how much rain will
fall during the growing season four months later, and then they set their planting date accordingly. Mark Cane
of Columbia University helped devise the modern system of forecasting El Nino and recently studied the Andean
farming practice.
“This is a region which experiences drought during the rainy season, the growing season of an El Nino year. So
if you could predict El Nino, you would expect drought in this area. And if it’s an El Nino year, it also turns out
that it will be harder to see this constellation on June 24th.”
That’s because El Nino causes more water vapor in the sky at this time of year. Cane says the Andean farmers
also chose just about the perfect night for predicting future rainfall by stargazing.
“It turns out that this is just about the best time you could pick to make this observation, if what you’re relying
on is a connection between El Nino and how visibility is going to be changed. That link is less strong a month
earlier or a month later.”
So, by checking the visibility of the Pleiades, the farmers of the Andes could get a hint of future weather
patterns.
“They did a marvelous job of using all the information available to them to come up with a system that works.”
Pulse of the Planet is presented by DuPont, bringing you the miracles of science, with additional support
provided by the National Science Foundation. I’m Jim Metzner.