Galápagos penguins find a cool refuge in a warming world

I’ve often wondered whether the Galápagos are so intensely cherished in the scientific community because of something inherently interesting about the biodiversity there, or whether it’s simply an accident of where the HMS Beagle happened to stop, delivering Charles Darwin onto its shores. Islands are biodiversity wonderlands in general, after all, and there is perhaps as much interesting wildlife to find on California’s Channel Islands or on the Seychelles. But it turns out that there is something unique about the archipelago: it lies precisely on the equator. And despite its location firmly in the center of the tropics, it’s home to a variety of species we typically associate with colder habitats, like penguins and fur seals. And that’s all thanks to a quirk of its geography.

The equatorial undercurrent (EUC) is an invisible undersea river that pushes one thousand times more water from east to west around the globe than the mighty Mississippi River, and it’s found just three hundred feet below the surface of the Pacific Ocean. Blocking its path one thousand kilometers from the coast of Ecuador sit the Galápagos. Once the EUC hits the islands, its cold water is deflected towards the surface. These upwellings, as they’re called, bring along a smorgasbord of nutrients to the sea’s surface, where they get gobbled up by plankton, which get gobbled up by fish, which are themselves then get gobbled up by penguins and other predators. The upwelling is strongest between July and December, which coincides with the penguins’ breeding season. All those fish provide the penguins with the energy necessary for breeding and to feed their newly hatched chicks.

According to research conducted by Woods Hole Oceanographic Institute climate scientist Kristopher Karnauskas and his colleagues and published online this week in the journal Geophysical Research Letters, changes in wind patterns over the past few decades have caused the EUC, and therefore the upwelling, to edge slightly north. And that’s been good news for the penguins there. The Galápagos penguin Spheniscus mendiculus is both the most critically endangered penguin on the planet, and also the most northerly.

In the 1980s, the cold pool, where surface temperatures remain below 22 degrees Celsius (71 degrees Fahrenheit) just barely touched the southernmost ends of Isabela and Fernandina islands. By 2014 it extended across the entire western edges of both islands. It’s perhaps no coincidence that two thirds of the penguins live on the southwestern tip of Isabela, where the surrounding seas are the most frigid and the upwelling the most intense. As the islands have become more habitable for the cold-loving birds, offering better breeding grounds and more feeding opportunities, their populations have increased.

67% of Galapagos penguins live along the stretch of Isabela Island highlighted in green, right along the coldest part of the upwelling just south of the equator.

67% of Galapagos penguins live along the stretch of Isabela Island highlighted in green, right along the coldest part of the upwelling just south of the equator.

At one time, there were some 2000 penguins living on the Galápagos, but a particularly severe El Niño in the early 1980s – a weather pattern associated with unusually warm sea surface temperatures – caused the population to crash to around 500 individuals. Dogs and cats that were introduced to the island further caused problems for the nesting seabirds, and invasive black rats ate up lots of their eggs. But since efforts were made to control those invasive species, the penguins have managed to rebound and in 2014 there were around one thousand of the swimming birds. While the doubling of their population was aided by human intervention, it wouldn’t have been possible without increase in available habitat made possible by the movement of the cold pool. The researchers base their argument on thirty-three years of data on local sea surface temperatures combined with penguin population estimates.

The researchers argue that these continuing trends generate important consequences for conservation initiatives in the area, like reintroduction programs or the establishment of marine protected areas (MPAs). Elizabeth Bay, on Isabela, has already been identified as a possible location for an MPA. This research suggests that the proposal ought to be expanded northward. Since the cold pool will probably continue moving northward, such protections would stand to benefit not just penguins, but also marine iguanas and endangered Galápagos fur seals.

While most scientific and media attention has been placed on the impacts of warming oceans on wildlife, this study is an important reminder that local trends may not always mirror global patterns, even while the latter directly influences the former. “The daunting challenges of understanding the tropical Pacific response to global warming cannot be overemphasized, but the local dynamics and ecological response playing out in the Galápagos is a cautionary tail in understanding other seemingly obvious biophysical interactions,” writes Karnauskas. Indeed, the majority of marine life is predicted to suffer due to the warming and acidification of our planet’s oceans associated with global climate change, but there will undoubtedly also be isolated spots where atmospheric and oceanic conditions combine in just the right way to allow ecosystems to thrive instead. “It’s a timely reminder that nature makes the rules and biology finds the loopholes.” – Jason G. Goldman | 05 August 2015

Source: Karnauskas, K. B., Jenouvrier, S., Brown, C. W., & Murtugudde, R. (2015). Strong sea surface cooling in the eastern equatorial Pacific and implications for Galápagos Penguin conservation. Geophysical Research Letters. DOI: 10.1002/2015GL064456.

Header image: Galapagos penguin via Flickr/Dagget2