What El Niño means for the Galápagos

Map of annual sea surface temperature and distribution of penguins at the Galapagos (map from climate.gov, adapted from original in Karnauskas, et al., 2015.)
Annual average sea surface temperature from 1982-2014 and penguin distribution (black lines). Nearly 70% of Galápagos penguins live where waters are coldest. Map from climate.gov, adapted from the original map by Karnauskas, et al., 2015.

During our strangely warm and “yo-yo” winter it’s interesting to realize we’re not the only ones affected by this year’s El Niño.  The Galápagos Islands in the Pacific Ocean, 620 miles west of South America, are having a much wilder time of it.

Though located on the equator the Galápagos have a cooler and drier climate than you’d expect because of an important ocean current and the prevailing wind.

The Equatorial Undercurrent (also known as the Cromwell Current) is a wide river of cool water moving west to east from Indonesia to South America, 300 feet below the surface.  Because the Trade Winds blow east to west they push surface water away from the archipelago’s western shore.  When the Equatorial Undercurrent reaches the islands it wells up to fill the surface void and effectively lowers sea surface temperatures west of the islands (see map above).

Cold water is good.  It supports more phytoplankton (tiny chlorophyll-producing organisms) than warm water and that supports the entire food chain all the way up to seabirds, mammals and unusual reptiles:  blue-footed and red-footed boobies, Galápagos penguins, Galápagos fur seals and marine iguanas to name a few.

As proof that cold water is good, the map above shows that Galápagos penguins live where the water’s cold. That’s where the fish are.

Galápagos Penguin, Galápagos Islands, Ecuador (photo from Wikimedia Commons)
Galápagos Penguin, Galápagos Islands, Ecuador (photo from Wikimedia Commons)

El Niño changes everything.  The trade winds subside or change direction, the undercurrent no longer wells up and sea surface temperatures rise. The warmth causes a drop in nutrients and the entire food chain suffers.  Fish populations drop.  Seabirds, mammals and, yes, penguins starve.

This year’s El Niño began forming in mid 2014 and was even then so intense that seabirds were starving off the coast of Chile in June 2014.  (see photo on the ABA Blog)

However, something good does comes of El Niño.  In the Galápagos there’s a population boom among land-based birds.  There, the rainy season is the breeding season and El Niño brings rain, sometimes quite a lot of it.  During the strong El Niño of 1982-83, cactus and Fortis finches (Darwin’s finches) bred like crazy, increasing their populations by 400%.

While immensely bad for some species, it’s very good for others.

That’s what El Niño means for the Galápagos.

 

(map from Climate.gov blog, El Niño and the Galápagos. Photo of Galápagos penguin from Wikimedia Commons.  Click on the images to see the originals.)

For more information see these sources:
* The Beak Of The Finch by Jonathan Weiner, especially pages 100-104.
* Climate.gov Blog:  El Niño and the Galápagos by Kris Karnauskas.
* Climate of the Galápagos Islands by Chris Ader, University of Maryland

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