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The Changing Climate, ENSO, and it’s Effects on the Wildlife of the Galápagos Islands

Figure 1: Bartolomé Island at sunset. (Author)

Claire Louise Smythe

Professor Bill Durham - Sophomore College: Evolution and

Conservation in Galápagos

Stanford University

15 October 2018

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Abstract:

The Galápagos are known for their incredibly unique biodiversity and fascinating

modifications endemic species have developed to fit harsh living conditions. A contribution to

these harsh conditions is the El Niño Southern Oscillation, which brings two events to the

Galápagos, El Niño and La Niña. These weather events can drastically influence the populations

of these species and have raised concern in the scientific community as these islands are seen as

the best example of evolution sciences. Two hypothesis have emerged from this issue. The first

hypothesis is El Niño and La Niña are becoming more frequent over time with increasing

intensity due to rising global temperatures. The second hypothesis is that these extreme ENSO

occurrences will increase such that Galápagos species will no longer recover their populations

and be pushed into extinction. This report studies how climate change alters the frequency and

intensity of these ENSO events and what effect this change will have on the Galápagos. Points

are also offered on the future actions necessary to protect these vulnerable species from

extinction and a discussion on the current status of these species, as well as the importance of

preserving these species.

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Introduction

A beach with sand made of coral chunks. A Swallow-tailed Gull screeching and flapping

at a Nazca Booby invading their nest while you watch from six feet away. A tortoise munching

peacefully on a green field while another wallows in a shallow pond. A swarm of Golden Rays

gliding beneath your flippers. Each of these memories came from the Galápagos Archipelago,

where tourists, researchers, and residents alike marvel every day at the incredible species that

make these islands their home. The Galápagos Islands are unique in their formations and

locations, and the species on the islands have unique adaptations not seen anywhere else in the

world. In other words, the endemic species of the Galápagos are fascinating.

Figure 2: A tourist watches a marine iguana crawl across the sand. (Samuel Price).

Each island has a collection of species who have adapted to the surrounding environment.

One of the main threats to species’ survival in the Galápagos is ENSO, El Niño Southern

Oscillation. It is a cycle of two weather phenomenons, El Niño and La Niña. Due to rising global

temperatures, scientists believe that ENSO will undergo serious change, since it is altered by

pressure and temperature differences across the Pacific Ocean. There are two hypothesis that

have emerged from this theory. The first hypothesis is due to rising global temperatures, EN and

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LN events are becoming more frequent with increasing intensity. The second hypothesis is that

these changing ENSO events are harming Galápagos species enough that their populations are

dropping to extremely low numbers and threatening extinction. ENSO mechanisms, general

climate change, and ENSO’s affect on the world will be evaluated and linked to the previously

mentioned theory to provide background for the evidence to support the hypotheses.

Figure 3: A tourist stands on a cliff overlooking the Pacific Ocean. (Maisam Pyarali)

Climate Change:

Climate change as a global occurrence has been tracked as global temperature increases

over the last few centuries. There have been numerous direct reactions caused by the thickening

of the atmosphere from CO2 emissions and other greenhouse gasses. Temperatures on land and

sea temperatures have both risen in the last century, ice caps are smaller than previous years,

evidence of decreased snow cover and shorter freezing of lakes, and the rising of the sea level are

all noted changes (Trenberth et al. 2007). Scientists are still unsure of the full extent of the

effects climate change will have on the earth, but an increase in sea surface temperatures and

land temperatures could have a direct relationship on the SOI across the Pacific Ocean.

Additionally, climate change has affected parts of the globe differently. Sea surface temperatures

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have been increasing at a slower rate than land surface temperatures, which changes the pressure

ratio across the Pacific ocean (Trenberth et al. 2007).

Figure 4: Graph of increasing global temperature anomalies. (Lindsey et al. 2018)

What is ENSO?:

ENSO, El Niño Southern Oscillation, includes both the El Niño and La Niña phenomena.

One of these phenomena is caused when the difference in atmospheric pressure is great enough

that winds shift to change the movement of the different ocean waters. This pressure difference is

defined by the Southern Oscillation Index, SOI. When the SOI is greater than positive 1 it is an

La Niña year, and below negative 1 it is an El Niño year (National Centers for Environmental

Information (NCEI), (2018).). These differences in pressure create wind, which will shift from

high-pressure and high temperature areas to low-pressure and low temperature areas. During the

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ENSO cycle, EN and LN create extreme weather events. During La Niña events, there are

extreme droughts on the land masses on the eastern parts of the Pacific ocean, and cyclones and

heavy flooding on the western landmasses. There is also evidence that a strong La Niña creates

extreme hurricanes in the Atlantic (Cai et al, 2015). La Niña occurs mainly after the heat

discharge of the El Niño events. The reemergence of the cold currents are expedited after an

extreme El Niño with westward and poleward surface currents and increasing easterly winds

(Cai et al, 2015).

Figure 5: El Niño wind patterns (Thomson Higher Education, 2007)

EN and LN Around the World:

The El Niño Southern Oscillation affects weather events and tropical storms around the

world. ENSO affects tropical storms around the world because the shifts in wind and pressure

cause changes in other areas. Tropical storms have seen an increase in the last 45 years, in both

intensity and frequency. Hurricanes level 4 and 5 have increased 75% with the North Pacific,

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Southwest Pacific, and Indian Ocean being most affected (Trenberth et al. 2007). Additionally,

storms in the North Atlantic have also increased (Trenberth et al. 2007). The past three years,

2015, 2016, and 2017, have been some of the warmest years on record, and these increased

temperatures usually occur in the absence of an El Niño occurrence that year (Lindsey, 2018). La

Niña events drop global temperatures (Lindsey, 2018). During El Niño years, hurricane

frequency in the Atlantic drops but increases typhoon occurrences in the Northwestern Pacific

(Trenberth et al. 2007).

EN and LN and the Galápagos (El Niño and La Niña side by side):

El Niño brings heavy rainfall and warm currents from the southwest Pacific to the

islands, which destroy marine food sources for many Galápagos species. La Niña acts like an

opposite event to El Niño, restoring cold currents and causing drought in the islands.

Figure 6: Marine Iguanas on Española Island, September 15, 2018 (Author)

Marine Iguanas are one example of a species severely impacted by El Niño. Their diet

consists of the algae that lives on the rocks deep underwater. This algae depends on the cold

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Cromwell current to deliver nutrients to ensure flourishing algae populations. When El Niño

brings warm water to overpower the Cromwell current, the algae population almost disappears

and the iguanas begin to starve. Over the course of an El Niño, which usually lasts over a year,

marine iguanas who cannot survive the extreme fasting will die out (Durham, Marine Iguanas

2018).

Studies on Climate Change Effects on ENSO:

ENSO events have been carefully tracked in the past seventy years, and interest in

studying ENSO increased after the severe 1982-83 El Niño that had devastating effects.

Numerous attempts have been made to model ENSO and apply predictive temperatures to track

how EN and LN will change with increasing global temperatures.

The research team lead by Wenju Cai ran two studies on ENSO, one study on El Niño

and its relationship with climate change and one

study on La Niña. They argued that two separate

research projects were needed because the two

events behave differently and not in perfect

opposition, as seen in Figure 8 (Cai et al, 2015).

They used similar procedures for their analysis.

The group used climate modeling and ENSO

simulations to track how EN and LN will change

over time, and to determine if that change is Figure 7: Relationship between two

already occurring. The group noted that components (Cai et al. 2015)

extreme LN events occur after EN events.

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They defined an extreme EN and LN as an anomaly where the first and second

components, wind stress vector and sea surface temperatures, are greater than 1 standard

deviation. They used empirical orthogonal function analysis to create these components and

arrange the data in scatter plots. Where the data fell over the threshold of 1 for both values, it was

classified as an extreme event.

Figure 8: Oscillation Index Over Time (Golden Gate Weather Services, 2018)

After applying this analysis, it was concluded that the occurrence of an extreme LN event

was increasing over time. Using a threshold of 1.75 standard deviations, the likelihood of an

extreme LN event increased from once every 23 years to once every 13 years (Cai et al. 2015). It

was also noted that 75% of extreme LN events occurred after extreme EN events.

They used a control set of data 1900-1999 and a climate change set of data 2000-2099 to

compare the ENSO events. The data was plotted for the control data using temperature and the

Niño4 index. They used the Niño4 index because the behavior was identical in comparing the

intensity of the events. When a standard deviation of 1.75 was applied to the Niño4 data, the LN

events of 1988-89 and 1998-99 were noted as extreme. When the same process was applied to

predict future LN events, there was a clear increase in extreme LN events. Rainfall was also

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compared between the control and the climate change model and in the western parts of the

Pacific there was an increased amount of rain predicted due to LN events in the future.

Figure 9: Scatterplots of Control and Climate Change data (Cai et al, 2015)

Hypothesis 2: How Galápagos Species Respond to ENSO

There are many species on the Galápagos islands that are negatively impacted by the warm

currents brought by El Niño. My second hypothesis is as El Niño events increase in intensity and

frequency, the species will have difficulty in recovering.

Two species drastically affected by the EN event are the Galápagos Penguin, Spheniscus

mendiculus, and the Flightless Cormorant, Phalacrocorax harrisi. The IUCN lists the Galápagos

Penguin as endangered and the Flightless Cormorant as vulnerable, and it was noted for both

species that future El Niño events could devastate their population and ability to recover (IUCN).

These two species depend on the health of the marine ecosystem surrounding the Galápagos

islands. As a result, when the warmer waters during EN events engulf the area, food is scarce as

fish migrate to cooler water or die as a result of the lack of nutritional algae (Durham, Marine

Iguanas, 2018).

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Figure 10: Flightless Cormorant (Tui De Roy)

It is noted that there is some recovery after each EN event during LN when the colder

waters return and marine food sources are abundant for the penguins and cormorants, but there is

concern that over time, these species will not be able to recover from extreme El Niño events if

they increase in frequency.

The graph in Figure 12 describes the population trends of the Flightless Cormorants and

the Galápagos Penguin in relation to EN and LN events. Over time, the populations are

fluctuating, but the amplitude of the population never surpasses the old population numbers

decades before (Durham, Penguins and Cormorants, 2018). These trends are concerning because

it indicates that the cormorants and penguins are already struggling to recover in these current

conditions.

La Niña restores the cold currents to the islands, but if

both ENSO events increase, then La Niña events will last longer

and deprive the islands of water, which will provide additional

stress on the recovering species. As noted in Figure 12, both the

penguins and cormorants are struggling to restore population

numbers.

Figure 11: Galápagos Penguin (Tui De Roy)

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Figure 12: Population change over time due to ENSO events. (Durham, Cormorants and

Penguins, 2018)

Other Species Affected By ENSO:

The Cormorants and Penguins are two examples of species that are negatively affected by

El Niño. However, EN has an island-wide effect. The waved albatross, Diomedea irrorata, had a

60% egg desertion during the 1982-83 El Niño and the fur seal pups, Arctocephalus

galapagoensis, all died except for one (Merlen). The ICUN has compiled a list of the species

located in the Galápagos and determined the probability of extinction. The data was complied

into a Venn Diagram in figure X to compare the factors of extinction and El Niño.

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Figure 13: A Compilation of Endangered species from El Niño and outside influences. (Author)

The species in the endangered circle are those that are listed in the ICUN as endangered

and the species in the “Decline from El Niño” have been listed with El Niño as a serious

influence on population survival, usually based on the eradication of food sources (Holmgren et

al. 2001). The combined circles are those who are both seriously endangered and seriously

affected by El Niño events and therefore need the most attention. This diagram is not complete,

but contains many of the most popular and well known species in the Galápagos.

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Figures 14 and 15: Left: The Waved Albatross, (Author) Right: Galápagos Sea Lion Pup. (Author)

During an El Niño there is a pattern in the islands’ response to EN and LN. During EN

years, shrub cover increases dramatically and can allow plants to recover from long LN droughts

(Holmgren et al. 2001). Different species are more populous based on food production. During

wet years, plant-eating species are more common while scavengers are more likely to survive

drier years (Holmgren et al. 2001). The effect of the EN and LN rotation can have long term

effects on the food chain, where bottom-up population decrease can effect even the most stable

of species in the Galápagos, like the Galápagos hawk. Darwin’s finches do best during the EN

years, proving that EN does not have a negative effect on every species in the Galápagos

(Holmgren et al. 2001).

Figure 16: A small tree finch. (Bill Durham)

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Conclusions:

This predictive information is important because it will allow conservationists and

scientists to better protect potentially vulnerable species. By knowing the species most at risk

under increasing ENSO events, resources can be spent to create a protection plan for these

species. The Galápagos are often seen as an important location for understanding how evolution

and the design for reproductive fitness happens over time. The unique ecosystems and location of

the island creates highly traceable adaptations that have helped scientists further understand how

evolution changes species over time. As such, it is in the best interest of those interested in

studying evolution to promote the continued survival of these unique species. This effort should

not be one solely undertaken by researchers however. The Galápagos Islands are seen as the

birthplace of evolutionary thought, and the preservation of a location is argued by many to be

important for the studies of future generations. Even while many of these species are negatively

affected by natural phenomena, human impact still has a detrimental effect on many species

around the globe, and continuing global warming will change how these species reproduce and

evolve. One may argue that there is no real benefit to preserving creatures that have no direct

influence on human resources, however as a global community with the resources to preserve

these threatened species, one should not remain passive.

Acknowledgements:

I would like to thank Bill Durham for providing an incredible education on the

ecosystems of the Galápagos. I would also like to thank the SCAs Caroline and Neil for assisting

me in the presentation and compilation of this research. Lastly I would like to thank Stanford

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Travel Study and my fellow Sophomore College classmates for creating an unforgettable

experience to one of the most fascinating places on Earth.

Citations:

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Cai, W. et al. Increasing frequency of extreme La Niña events under greenhouse warming. Nature Clim. Change 5, 132–137 (2015).

De Roy, Tui. Flightless Cormorant with nesting material in beak. (n.d.). [image].

De Roy, Tui. Galápagos Penguin Braying. (n.d.) [image].

Durham, Bill. “Beautiful on the Inside (Marine Iguanas).” Presented 4 September 2018.

Durham, Bill. “Challenged As Never Before (Galapagos Cormorants and Penguins).” Presented 8 September 2018.

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