... 1997 El Niño in Galapagos

A SPECIAL REPORT FROM THE CHARLES DARWIN RESEARCH STATION - 1997 EL NIÑO IN GALAPAGOS

Introduction

This is a report prepared by the Charles Darwin Research Station on the current situation in Galápagos, following the detection of climatic anomalies that have been identified by national and international meteorological agencies as effects of El Niño.

Characterization of the El Niño event

An "El Niño" event occurs when warm ocean currents appear on the Pacific coast of South America during the southern hemisphere summer. The term El Niño (Spanish for "the Christ child") was coined by South American fishermen centuries ago who observed the arrival of these currents at the end of December, near Christmas.

According to observations in recent years, the phenomenon occurs at intervals of 2 to 10 years and is characterized by abnormal conditions in the surface layer of the ocean and in the atmosphere above during a period of 12 to 18 months.

Under normal climatic conditions, the surface temperature of the tropical Pacific Ocean near Australia and Indonesia is about 8 degrees C above the temperature measured during the same period along the coast of South America. Similarly, the sea surface is approximately 50 cm higher in the western than in the eastern Pacific. As a consequence, heavy rains occur in the western Pacific, while in the East, a dry climate and little precipitation predominate.

During an El Niño, there is a weakening of the trade winds that generate normal oceanic circulation. Consequently, masses of warm water gradually begin to move from the coasts of the western Pacific toward the East, reaching the coast of South America about six months later. This displacement is accompanied by a relative cooling of the water in the western Pacific region.

While this is occurring in the ocean, an alteration occurs in the pattern of atmospheric pressure, which decreases over the eastern Pacific and increases over the West. These alterations in atmospheric pressure over great distances produce changes in wind direction and velocity, altering the areas where tropical rains fall. In the ocean, there is a weakening of the equatorial countercurrent that carries cold water from the Peru current (also known as the Humboldt Current) toward the west. The weakening in this cold current favors the transport of warm waters toward the coast of South America.

The presence of unusually warm seawater as well as the atmospheric changes produce an unusual increase in the quantity of precipitation along the coast of South America and in Galápagos, as well as prolonged drought in Southeast Asia and Oceania.

Changes in temperature influence the salinity of seawater, thus altering environmental conditions in marine ecosystems. In coastal ecosystems, the anomaly has important impacts on biological systems that are linked to the sea.

According to the data from the anomalies registered over the long term, after an El Niño event it is highly probable that extreme drought will occur on the coasts of South America.

There are not yet detailed patterns that permit us to predict the intensity of an El Niño event. Historical data show that the event of 1982-83 was totally irregular, because it was not preceded by the atmospheric changes characteristic of El Niño events registered during the previous decades. In the same way, other events have had varied consequences, as for example that of 1977, when during the month of January 85% of the territory of the United States was covered by snow (snow even reached Miami, Florida); also, the phenomenon did not generally occur over several years between 1990 and 1995, the longest period without El Niño in the 130 years of existing observations.

El Niño of 1982-1983 in Galápagos

In 1982 and 1983, the phenomenon of El Niño was so forceful that scientists named it "the event of the century". Broad zones of the Ecuadorian coast suffered serious problems, which included the loss of human life and important economic losses due to floods and landslides.

Galápagos was no exception. In 1983 the meteorological station of the Charles Darwin Research Station registered 201 days with measurable precipitation, and total precipitation for 1983 was 2768.7 mm. This is compared to normal years in which measurable precipitation occurs on about 50 days and total annual precipitation averages 385 mm (based on measurements between 1965 and 1996, excluding values from 1983). Graph 1 displays precipitation data from 1965 through 1996. The notable peak occurred in 1983 during which El Niño reached its greatest intensity.

The mean monthly sea temperature measured by the same station reached 28.6C in the month of March compared to normal years in which the mean temperature of this month is 25.5C (based on measurements between 1965 and 1997, excluding values from March 1983). Graph 2 displays mean annual sea temperatures observed at the Charles Darwin Research Station between 1965 and 1996. The peak observed in 1983 is clearly visible and is the highest mean annual sea temperature observed during 31 years of observations.

Graph 3 displays changes in mean annual air temperature observed at Charles Darwin Research Station. Again, high temperatures peaked in 1983 when the annual mean was 25.7C, compared to an average annual mean of 23.8C in normal years (based on measurements between 1965 and 1996, excluding values from 1983). It is worth mentioning that the highest mean air temperature observed in 1983 occurred in March, reaching 27.8C.

The El Niño of 1982-1983 brought changes that in certain cases can still be observed. The following details some of these changes.

Visitor Sites Some visitor sites in Galápagos National Park became inaccesible due to the exuberant growth of vegetation, the destruction of paths, and the lack of safety at landing sites; additional factors such as the increase in numbers of the stinging little fire ant (Wasmannia auropunctata) will be discussed below. Similarly, some areas of the Galápagos archipelago possessed oceanographic conditions that made navigation difficult, while others enjoyed unusually calm conditions that favored marine transport.

Fauna The fauna of Galápagos was affected in various ways by the El Niño event of 1982-1983. Some birds and marine mammals, as well as marine iguanas, suffered visible decreases in their populations, principally due to the following factors: a) mortality, especially caused by the absence of food and by increased incidence of illness; b) reproductive failure, probably related to the lack of food; and c) displacement to other locations. The effect was particularly notable in the colonies of blue footed boobies (Sula nebouxii) on Española island, in the nesting of waved albatross (Diomedea irrorata) on the same island, in the populations of endemic flightless cormorants (Nannopterum harrisi) and Galápagos penguins (Spheniscus mendiculus), as well as in the populations of marine iguanas (Amblyrhyncus cristatus) throughout the archipelago. On the other hand, populations of land birds exploded; for example, the Galápagos finches reproduced in great numbers due to the abundance of food on land. Table 1 describes how the 1982-83 El Niño event affected the fauna of Galápagos

Effects of the 1982-83 El Niño event on the fauna of Galápagos

1. Marine life

Flightless cormorant (Nannopterum harrisi)
The population of the flightless cormorant suffered a 45% decrease. The impact was most notable on Fernandina island, where more than 100 individuals were found dead. At the visitor site of Punta Espinosa the disappearance of these birds was obvious. By the end of 1983, reproduction had begun again and apparently had stabilized in 1984.

Galápagos penguin (Spheniscus mendiculus) The population of Galápagos penguins suffered a 78% decrease. More than 100 dead individuals were registered in censuses, but scientists also noted a displacement of groups of penguins toward other places in the archipelago. According to the most recent reports from the Darwin Station, the number of penguins still has not reached the population size that existed before the event. For that reason, a repeat of the conditions of the 1982-83 El Niño could have serious repercussions on the current population of the Galápagos penguin.
Waved albatros (Diomedea irrorata) The population of waved albatross on Española island suffered a total reproductive failure in 1983. Of the females present, 15% tried to nest but apparently failed to hatch any chicks. The rains of May and June of 1983 prevented normal incubation. About 60% of the area in which albatross usually nest was made inaccesible by the overgrowth of vegetation. Nevertheless, once conditions improved in July, scientists observed an unusual frequency of albatross mating dances.

Great frigatebird (Fregata minor) The situation of the frigatebird colonies was different on each island. On Genovesa island matings and nesting during March and April 1983 were frequent; in August of the same year, the percentage of nesting had decreased to 6.1%. On Española, however, the percentage nesting was zero, while on Pitt islet 65% of the pairs of frigatebirds were nesting.
Blue-footed booby (Sula nebouxii) The populations of this species of booby diminished considerably. There was an elevated movement of individuals to other locations in the archipelago, but mortality was high and very obvious especially around Fernandina island. By October, 1983, a recuperation in reproductive activity was observed.

Marine iguanas (Amblyrhynchus cristatus) Populations of marine iguanas suffered generalized and conspicuous mortality of 45 to 70%, according to the location. Marine iguanas that survived had an average reduction of 30% in their body weight. These effects derived from the replacement of their habitual food by a species of marine alga that they could not digest. After the most intensive phase of the El Niño event concluded by August, 1983, the populations of marine iguanas recuperated rapidly.

Sea lions (Zalophus californianus and Arctocephalus galapagoensis) Populations of sea lions suffered a general decrease throughout the archipelago for three principal reasons: a) an elevated mortality among juvenile sea lions, especially from abandonment; b) increased incidence of diseases, especially those affecting the skin; c) migration to other locations.

Whales and porpoises In general, a marked absence in whales and porpoises was noted; it was assumed that they migrated to areas where food was more abundant.

Other marine animals Changes occurred in the composition of marine communities and abundance of various species. Although abundance of some species of fish diminished, other species (typical of warmer tropical waters) appeared. There was increased and generalized mortality among corals.

2. Life on land

Darwin's finches (Fringillidae family) The 1982-83 El Niño event gave rise to a considerable and conspicuous increase in the populations of various species of finches throughout the archipelago. The increase occurred because the birds nested more frequently, apparently due to the greater abundance of food. However, the El Niño rains caused many nesting failures and increased predation on chicks, especially by Galápagos mockingbirds (Nesomimus spp.).

Mockingbirds (Nesomimus spp.) As in the case of the finches, populations of mockingbirds increased as a result of the El Niño event. There was increased abundance of food; predation on finch nests was notable. However, the mockingbirds were more susceptible to heavy rains which destroyed mockingbird eggs and killed recently hatched chicks.

Land iguanas (Conolophus spp.) There are no data on the reaction of land iguanas to the El Niño event of 1982-83. However, in the drought years that followed, populations suffered increased mortality.

Giant tortoises (Geochelone elephantopus) The giant tortoises of Galápagos did not suffer notable population impacts. On Santa Cruz island giant tortoises migrated en masse from the highlands toward the lowlands. In the following years, measurements indicated that young tortoises grew more rapidly during the El Niño event than in normal years.

Flora Immediate effects were noted in the vegetation of the Galápagos islands where plant populations exploded in normally arid areas and demonstrated unusually rapid and exuberant growth in the highlands of some islands. Research carried out in the months following the end of the 1982-83 El Niño event showed that the excess rain apparently had produced more effects on the abundance and distribution of various species of plants than on their numbers; the conclusions of these studies indicated that no long-term effects were expected in some species, however, there would be alterations in the type of vegetation in certain ecosystems.

Changes in the vegetation varied according to the life zone and type of plants present. Generally, species of the arid zones reacted with much greater speed to the abundance of rainfall. Especially herbs and climbing plants took advantage of this new resource and expanded very rapidly. Similarly, enhanced germination occurred in seeds that had apparently been dormant in the soil for several months or years. Notable mortality occurred among adult individuals of the giant cacti in the genus Opuntia, as well as large Scalesia trees, which could not support their weight when their roots rotted due to excessive rainfall.

As measured by accelerated growth rates, plants in the most humid zones were less sensitive to increased precipitation than were plants in the arid zone. As in the arid zones, those humid zone species that benefited most from increased precipitation were herbs and climbers. Again, Scalesia was the genus that suffered greatest mortality of adult individuals (over 10 years old).

Introduced organisms During the 1982-83 El Niño event, observers noted increased abundance of introduced organisms that depend on the quantity of precipitation. Most noteworthy was the dispersal of two species of aggressive introduced ants, the little fire ant Wasmannia auropunctata and Tetramorium bicarinatum. The little fire ant demonstrated a particularly elevated rate of expansion, moving north on Santa Cruz island at the rate of approximately 0.5 km per year, compared to a normal rate of expansion of approximately 0.17 km per year (data taken between 1976 and 1982). The number of introduced rats (Rattus rattus and Rattus norvegicus) increased markedly in areas of the islands populated by humans.

Infrastructure of roads The infrastructure of roads was destroyed on various occasions; the highway to Baltra island (crossing Santa Cruz island from south to north) as well as various local roads had to be repaired continuously. The interruption of traffic caused a scarcity of goods in the highlands of the populated islands; similarly, the safety of vehicles that used the highway to Baltra was affected, especially in the section that leads to the farming village of Bellavista.

Generation of electricity Frequent power outages occurred because the generators and transmission lines were not prepared for the great quantity of rain. The uncustomary occurrence of electrical storms was an additional problem.

Public health The general health in the populated area suffered a serious setback. According to published reports, continuous humidity resulted in an unusually high incidence of skin and gastrointestinal diseases. The heavy rains carried sediments that contaminated drinking water supplies of the population centers.

Supplies During the 1982-83 El Niño event, there was a great scarcity of various basic household staples, due both to the impossibility of reliable transport within and among the islands, and to the scarcity of the same products on the continent of South America.

El Niño in 1997

In 1997 various global meteorological and oceanic networks detected climatic and oceanographic anomalies that began to develop in March of 1997. The first warnings were issued during the second half of the year, indicating that a phenomenon was approaching which could surpass what occurred in 1982-83. Subsequent measurements of sea temperatures along the equatorial portion of the Pacific displayed a growing displacement of warm water that was moving toward the western coasts of Central and South America. At midyear the masses of warm water had reached these coasts with temperatures between 3 and 5C above normal. Almost simultaneously came reports of strong rains in Chile and Peru.

In southeast Asia the predictions have been accurate, as the worst droughts in decades have already killed dozens of victims and caused forest fires (whose effects have been felt in various countries and have occasioned warnings to tourists by western governments) and economic upheaval throughout the world.

In the Galápagos islands, the second half of 1997 was marked by abnormal climatic conditions, with patterns more similar to those expected early in the year rather than in July, August, or September. Satellite imagery has displayed an increase by more than 5C in the surface sea temperature of the region. Similarly, the meteorological station of the Charles Darwin Research Station has registered an abnormal increase in the mean monthly sea temperature beginning in May, 1997. Graph 4 displays this increase, compared with a year that was considered to be normal (1965) and with the year previous to the El Niño event of 1983.

The year 1997 has been characterized by stong rains during the first half of the year; Graph 5 displays total monthly precipitation through September, compared with the data for 1965 and 1982. The difference between 1997 and 1982 is noteworthy. Despite the fact that the latter preceded the El Niño event of 1983, the difference in precipitation in April of 1997 and 1982 is almost 400 mm.

The air temperature measured by the Charles Darwin Research Station in 1997 is also various degrees above the normal temperatures observed in previous years. Similar to what is occurring in sea temperatures, 1997 is displaying patterns that differ from those which occurred in the pre-El Niño year of 1982. Graph 6 displays the mean monthly air temperatures for 1965, 1982, and 1997.

It is noteworthy that both the mean sea and air temperatures for the month of September, 1997 are the highest that have been measured in the 32 years during which the Charles Darwin Research Station meteorological station has operated. Similarly, over the same period the April, 1997 precipitation totals have been surpassed only by the rains of April, 1983 (434.2 mm).
Despite the unusual conditions when compared to other years, the climate of Galápagos during the third quarter of 1997 has been relatively stable. The quantity of precipitation has diminished as of July, and temperatures have been pleasant without being exceedingly hot. Although a strong breeze predominates, many boats report that the ocean has remained calmer than is usually expected during this period in normal years. Up-to-date data on wind velocity and direction measured in Puerto Ayora, Santa Cruz island, are available at Charles Darwin Research Station. Although no systematic study has been conducted on the fauna or flora at visitor sites of Galápagos National Park, no observations or reports have indicated any unusual mortality or changes in populations. In brief, the environmental conditions for the third quarter of 1997 are more favorable for tourist visits than in normal years.

Most current predictions indicate that the El Niño event will grow in intensity from October 1997 onward; according to recent predictions (first half of September, 1997), the event will reach its peak between March and May 1998. The duration of this event is not known with any certainty.

It is noteworthy that the different climate models that have predicted the El Niño event of 1997 have been relatively accurate by comparison with predictions in previous years. This probably can be attributed to the great number of meteorological and oceanographic measuring systems that were installed throughout the world after the El Niño event of 1982-83, and to the attention that El Niño has received in recent years. The international scientific community considers that the El Niño event of 1997 has been anticipated with greater precision than any other previous event of this magnitude.

From the point of view of economics, there is fear among the public about visiting the islands during this time. The Charles Darwin Research Station has received a constant stream of inquiries on whether or not visitors should come to Galápagos; inquiries come both from private individuals and companies and organizations involved with tourism in the islands. According to reports of local tour operators and the Galápagos Provincial Chamber of Tourism, up to now they have received a series of cancellations from companies that do not want to risk their reputation when faced with a potentially intense El Niño event in late 1997 or early 1998. On this subject, the Darwin Station considers that if a major event occurs, the conditions for tourism will be distinctive and may repeat the situation that occurred during the El Niño of 1982-83.

Similarly, there is concern about the physical and social effects that the El Niño event may have on the human population of the archipelago. In July of 1997 the Charles Darwin Research Station and Galápagos National Park Service published a document with suggestions on how to deal with the El Niño event; this document is available from the offices of both institutions.

Precautionary actions taken to date

In order to anticipate potential effects of an intense El Niño event in 1997-98, authorities have taken a series of precautions and measures, indicated in Table 2.

Precautionary actions taken to date in response to the El Niño event of 1997-98

Visitor sites in Galápagos National Park The Charles Darwin Research Station has carried out an evaluation of the infrastructure of the most heavily used visitor sites in order to provide Galápagos National Park (GNP) with a basis for establishing a contingency plan. Similarly, authorities of Galápagos National Park conducted a trip to other visitor sites and evaluated potential impacts of the El Niño event on landing and disembarkment of passengers at these sites.

Fauna and flora The Station has produced a proposal for an environmental monitoring plan that would permit possible effects of the El Niño on the fauna and flora of the archipelago to be determined during the event. Funding is urgently being sought in order to carry out this plan.

Introduced organisms Continuous observations on potential dispersal events and on expansion of the range of potentially noxious introduced organisms are included within the monitoring plan indicated in the point above. Similarly, the Darwin Station and Galápagos National Park have advised local authorities on immediate measures that they should take to prevent the proliferation of these organisms, especially rats and ants, in the areas populated by humans.

Infrastructure of roads and supply lines The infrastructure of roads on islands inhabited by humans has been radically improved. Most of the principal roads to airports and villages have been asphalted, therefore major impacts by heavy rains are not expected. Drainages have been built in high-risk sites and the highways possess systems to drain water away. There are three functioning airports and interisland air service operates, which guarantees transport of cargo and passengers in case the environmental conditions prevent traffic by sea.

Safety on board boats The principal tour companies have reported that they have taken additional precautionary measures to guarantee passenger safety in case they face potentially adverse climatic conditions.

Quarantine Advances have been made to install and carry out quarantine systems and programs, both in the airports and seaports and aboard seagoing vessels, in order to avoid dispersal of potentially damaging organisms from the mainland to the islands and among the islands.
Basic services and public health The authorities of the Province of Galápagos have taken preventive measures to improve the systems that provide water, energy and communications. Health authorities have begun campaigns to avoid the proliferation of tropical diseases.

Emergency procedures The civil defense committees of the Province of Galápagos have practiced evacuation drills; the various civilian and military sectors have held frequent planning meetings to face the situation.

Furthermore, it has been proposed that Galápagos National Park and the Charles Darwin Research Station draw up a contingency plan. This plan would include the following points:

1. production of a map of sites at risk of El Niño impacts, with different categories of risk (e.g., sites that are difficult to reach, sites to be closed, etc.);
2. a plan for intensive maintenance of sites at risk of being covered by vegetation or being destroyed by the impacts of the rain and tides;
3. an intensive monitoring plan for the sites most frequently visited;
4. alternate itineraries for tourism in case it is necessary to close one or more visitor sites;
5. a system to regularly provide information to tour operators about the status of the fauna and flora at the most heavily used visitor sites, in order to continuously update the information that tour operators can provide to passengers.

Conclusions

Based on current analyses, the following can be concluded:

1. The Galápagos islands are experiencing the visible effects of an El Niño event since the middle of 1997. However, although the environmental conditions are not typical for this time of year, they have remained stable during the third quarter of 1997 and are favorable for tourism.
2. Most climatic models and current predictions indicate that the El Niño event will intensify greatly during the last quarter of 1997, and will reach its maximum strength between March and May of 1998.
3. If the El Niño event reaches the intensity which has been forecasted, the Galápagos islands will experience impacts that may possibly exceed the intensity of those experienced during the 1982-83 event. These consequences include problems of sanitation, transportation, basic services, quarantine, and social problems, as well as changes in the Galápagos ecosystems.
4. A series of precautionary urgent measures has been implemented to counter the effects of what will probably be a very intense El Niño event.

Bibliography

1. CEPES, ¿Qué es el fenómeno de El Niño-Oscilación del Sur (ENSO)? (What is the phenomenon of El Niño-Southern Oscillation(ENSO)) , from the World Wide Web site http://ekeko.rcp.net.pe/cepes-el-nino/
2. ENN, Environmental News Network, El Niño Special Report, from the World Wide Web site http://www.enn.com/elnino/
3. Estación Científica Charles Darwin, Informe sobre estado de la infraestructura en sitios de visita del Parque Nacional Galápagos, septiembre de 1997, 3 pp. (Charles Darwin Research Station, Report on the status of infrastructure in visitor sites of Galápagos National Park, September, 1997, 3 pp.)
4. NASA/JPL, Press release: Independent NASA satellite measurements confirm El Niño is back and strong. September 16, 1997, received by Internet from news-release@www-onlab.jpl.nasa.gov
5. NOAA, El Niño/Southern Oscillation (ENSO), from the World Wide Web site http://nic.fb4.noaa.gov:80/products/analysismonitoring/ensostuff/index.html
6. NOAA, What is an El Niño?, from the World Wide Web site http://www.pmel.noaa.gov/toga-tao/el-nino-story.html
7. Robinson, G. and Eugenia del Pino (ed.). 1985. El Niño en las Galápagos, El Evento de 1982-1983 (El Niño in the Galápagos, the Event of 1982-1983), Charles Darwin Foundation for the Galápagos Islands, 534 pp.