An Evolutionary Test in a Changing Climate
Photos and Article by Kate Berry
Naturalist Charles Darwin once wrote, “It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change.” Today, the warming planet is bringing new evolutionary challenges to the Galápagos archipelago, the birthplace of Darwin’s theory of natural selection. The questions remain, in the era of climate change, will the unique life of the Galápagos survive the greatest evolutionary test yet?
Galápagos Islands, Ecuador – The equatorial sun shimmers across the black sand beach of Fernandina Island, the youngest and most volcanically-active island of Galápagos. The shoreline scuttles with life as hundreds of marine iguanas congregate into a dense mass of scales. Flightless cormorant, a strange product of evolution, dry their under-developed wings after their foraging boats in the frigid, oceanic waters. Ongoing seismic and volcanic activity and the confluence of three ocean currents, has led to the development of unusual and extraordinary life, found nowhere else on the planet. Over a century ago, it was here in the mystical Galápagos islands that Charles Darwin conceived a blueprint for the origin of species. However, not even Darwin could have predicted the evolutionary test that awaited the Galápagos. In an era of climate change, the extraordinary life of Galápagos may be no match for the whims of natural selection.
the Galápagos archipelago, consisting of 19 major islands and lying 960km off the coastline of Ecuador, exists as much in myth as on the map; often being referred to as being a living museum and showcase of evolution. Before they were the Galápagos, they were “Las Encantadas”, meaning “the enchanted ones”—inhospitable, isolated islands inhabited by the most bizarre life. However, even isolation has proven to fail in protecting them from human impact and climate change. As the world’s oceans warm from a changing climate, the Galápagos is a crucible. Not only does the string of islands sit at the intersection of ocean currents, they are in the cross hairs of one of the world’s most destructive weather patterns, the El Niño.
El Niño refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific. Scientists have found in recent years that climate change is not only increasing the frequency of such events, but also their severity. It is no surprise that UNESCO (The United Nations Educational and Cultural Agency) warns the Galápagos is one of the places most vulnerable to the impacts of climate change. Perhaps nowhere else on Earth is the cycle of life and death driven so dramatically by climatic events, with changes in temperature, rainfall, and ocean currents influencing life both on land and in the sea.
As the Earth warms at an unprecedented rate, scientists are racing to understand what the future of these mystical islands will look like. One of the most effective approaches is to take a step back in time nearly 40 years. October 1982 through to July 1983, the Galápagos Islands experienced the strongest El Niño‐Southern Oscillation event yet recorded, with heavy rains and a warm, unproductive ocean. During this period, seabirds stopped laying eggs and abandoned their nests. Large Marine Iguanas perished, while others shrunk their skeleton to survive – something that has not been documented ever in any vertebrate. Eight of every 10 Galapagos Penguins died, and the population of endemic Flightless Cormorants declined by 50%. Nearly all the Sea Lion pups and adult male Fur Seals perished. Storms flattened forests of Scalesia, giant daisy trees, and invasive plants overtook the land. The Galápagos damsel fish was wiped from existence.
The La Niña overturns everything and we witness a cycle analogous to a roller coaster: Deprivation. Recovery. Abundance. Repeat. However, the intensity and regularity of these climatic cycles is rising alongside ocean temperature. Since 1982, the world’s oceans have warmed by at least half a degree Celsius. Thus, in the visible future, human-induced climate change may push environmental conditions to new extremes, and the capacity for populations to respond to these changes remains largely unknown.
Evolution has led the life of the Galápagos in many unusual directions, however now the species must face their greatest evolutionary test yet. Perhaps the best studied example of the impact of the El Niño-Southern Oscillation on natural populations is the Marine Iguana. Marine Iguanas are known to inhabit the shoreline of all the major islands in Galápagos, where they forage almost exclusively on algae from intertidal and subtidal zones. During severe El Niño events, the coastal environment is dominated by algae species that the iguanas cannot digest. On some islands, this has led to extreme undernourishment of iguanas, changes in breeding behaviour, and mortality rates as high as 90%. Scientists discovered that these sea-going lizards also shrank, by reabsorbing their bones, to increase their chance to survive during the El Nino. Stress hormones are thought to trigger this process, but little more is understood about how the iguanas adapt. Nevertheless, this evolutionary mechanism could be central to their survival as El Niño cycles become more frequent.
Other species, such as Galápagos Sea Lions have devised new methods to hunt and changed their diets in response to changing climate. Scientists have observed Sea Lion chasing Yellowfin Tuna into coves and slaughtering them in the shallows; a species of fish that they have not been known to eat. Other animals have fewer options to change their diet. Blue-footed Boobies once lived primarily on Sardines, however, the sardine population plummeted in 1997 forcing the birds to feed on other species of fish. However, during an El Nino, there alternative food sources also disappear and the birds stop breeding. Sadly, this means that the Blue-footed Booby and many other seabirds may not come out of this as victors of climate change.
While warming temperatures threatens the existence of many of the Galápagos’ endemic species, invasive life flourishes. Today, the Galápagos is home to more than 1,430 introduced species, which is considered one of the greatest threats to the archipelago. During the 1997/1998 El Nino, the first frog was introduced to the archipelago, which now threatens to wreak havoc on the invertebrates of the Galápagos. The Fire Ant is another invasive species flourishing from the changing climate, feeding on the eggs of the emblematic Giant Tortoises, and even attacking the eyes and legs of the adults. In the misty highlands of the Galápagos, Chinchona shades and reduces native plants and, by changing plant-community structures, hurts endemic species such as the Galápagos petrel, with the unusual habit of burrowing into the ground to nest. Further, invasive blackberry has spread throughout the remaining forests, smothering the ground and preventing native seedlings from rising and finches from nesting.
So far, the unique life of the Galápagos has managed to hang in the precarious balance. But it seems for many that the increasing threat of climate change will prove to be too great of evolutionary test to win. As such, now more than ever, we must stand together to protect these threatened species and mitigate the effects of climate change on the Galápagos.