The major El Niño that has been brewing in the Pacific Ocean since 2014 has been parching parts of the Peruvian Andes, flooding neighborhoods in Paraguay’s capital and giving scientists an unprecedented opportunity to study the interplay of climate change and weather in a warming world.
But the region’s countries generally are coping better with the consequences than they have in the past, experts say.
“My impression is that most countries are better prepared than they were in 1997 and for sure than they were in 1982,” the last major El Niño years, says Walter Baethgen, who heads the regional and sectorial research program in Latin America for Columbia University’s International Research Institute for Climate and Society.
“There are better institutions, people understand better the expected impacts of El Niño [and] they have emergency systems in place,” Baethgen says. “I think in general people believe that it is better to use a risk-management approach [instead of] a crisis-management approach.”
Nevertheless, the impacts take their toll.
In Peru, where the mass of warm water that signals an El Niño has brought hard times to the country’s anchovy fishery, drought in the southern highlands is threatening crops. In Lima, a city of 10 million people that sprawls across a desert, officials are mulling steps to conserve water as reduced rainfall in the Andes Mountains diminishes rivers that the capital counts on as its water supply.
El Niño has also brought even drier conditions to northeastern Brazil, which was already in the grip of a long drought. Farther south, El Niño triggered the opposite effect, dumping rain that caused the Uruguay, Paraguay and Paraná rivers to overflow their banks, displacing some 150,000 people, many of them in the Asunción, Paraguay, neighborhoods known as the Bañados, which flood seasonally even in a normal year.
El Niño—named for the Christ child because it usually appears around December—brings warm ocean water from the western Pacific to the South American coast, a huge flow aided by a lull in westward-blowing trade winds.
Although the conditions occur every few years, they tend to make headlines every decade or so, when a particularly strong El Niño, such as the current one, occurs. That happened in 1982-83 and again in 1997-98. This time, sea-surface temperatures in the central Pacific Ocean began to rise in 2014, then dropped again. That happened several times before the “classic” signs finally appeared in 2015, signaling El Niño conditions that will persist into the first half of this year.
To Rodney Martínez, who heads the International Center for Research on the El Niño Phenomenon (Ciifen) in Guayaquil, Ecuador, that makes this one of the longest El Niños on record.
Meteorologist José Marengo, a senior scientist at Brazil’s National Center for Early Warning and Monitoring of Natural Disasters (Cemaden), disagrees, tracing the onset to 2015.
Once the full-blown El Niño took hold in 2015, however, it generally followed the classic pattern. Scientists predicted the drought in the Peruvian highlands, where farmers around Arequipa are watching crops dry up. Scientists also foresaw the reduced rainfall over already-parched northeastern Brazil and the heavy precipitation that fell in the River Plate basin.
Flooding forced more than 150,000 people from their homes in northern Argentina, southern Paraguay, parts of Uruguay and Rio Grande do Sul in Brazil.
In early January, water levels at Asunción rose to more than 25 feet (7.6 meters), some 10 feet (3.1 meters) above flood stage.
The Paraguayan Health Ministry declared an alert for mosquito-borne diseases, including dengue, chikungunya and zika, a virus new to the region that has spread rapidly in recent months. The zika virus is transmitted by the Aedes aegipti mosquito—the same one that carries dengue and chikungunya. It might be linked to cases of microcephaly—an abnormally small head and brain—in newborns and temporary paralysis in adults, although scientists are unsure of the connection.
Spared so far have been northern Peru and southern Ecuador, where past El Niño events have caused heavy rains and flooding. A high-pressure system over that region has kept precipitation away, although Martínez says that system is weakening and precipitation could follow.
Lessons from the past, combined with more precise forecasts and earlier warning, gave countries more time to prepare for the impacts of this El Niño than they had before the last two such events. Scientists will also be on the lookout for La Niña—the name given to colder-than-normal Pacific Ocean temperatures that have their own global impact, creating drier conditions on the western coast of South America and boosting precipitation in northern Brazil.
“People tend to think that in El Niño or La Niña years, you have more disasters than in non El Niño or La Niña years,” Baethgen says, adding studies have found that the number of disasters worldwide actually is not greater in those years. “What does change is that you have a better chance of predicting what can happen in various regions of the world,” he says.
Operators of the Salto Grande hydroelectric dam on the Uruguay River, for example, knew that they would have to manage a large flow of water because of heavy rains. In Peru, flood-control measures were taken after the 1997-98 El Niño, especially in the north, although that area has been spared so far this time.
El Niño’s warm waters disrupt the cold Humboldt Current that typically flows northward along the coast of Peru and is home to one of the world’s richest fisheries. Peru is known especially for the anchovies that sustain its huge fishmeal industry as well as marine wildlife, including sea lions, cormorants, pelicans, boobies and penguins.
The warmer water forces the anchovies to go deeper or move south in search of colder water.
Peru responded last year by limiting the anchovy catch, but commercial fishermen lobbied for an expanded season. Many of the fish caught late in the season reportedly were juveniles, says zoologist Patricia Majluf, a former vice minister of fisheries who now heads the Peru office of the nonprofit marine advocacy group Oceana.
That raises concerns about how quickly the population will be able to recover once water temperatures return to normal, she says.
Seabirds that nest on rocky headlands and islands are also suffering, according to marine biologist Carlos Zavalaga, who is monitoring birds and water temperatures at 16 sites along the coast.
In normal years, huge colonies of guanay cormorants (Phalacrocorax bougainvillii) nest on several dozen islands and headlands here, along with smaller numbers of pelicans and boobies. The birds build nests from their own droppings, and over time the accumulated guano can reach a depth of several meters. The residue, natural fertilizer which once sparked a war over islands where it abounds, is harvested on a rotating schedule and sold. This year, however, the cormorants are nesting and reproducing on only three of the 16 islands Zavalaga is monitoring, and numbers have plummeted at the other sites. The same thing happened during the major El Niño events in 1982-83 and 1997-98, but this is the first time a researcher has watched so closely.
“This is something that has never been done before,” Zavalaga says of his weekly report on bird populations and sea surface temperatures, which he posts on a blog.
He is also experimenting with aerial photos taken from drones to calculate the number of birds on the islands. Those records traditionally have been kept by guards on the islands, who count the birds in one area and extrapolate to estimate the total. He hopes the aerial count will be more precise.
Researchers are not sure where the birds go, Zavalaga says. Some probably migrate, while others die. He is watching to see whether the deep-diving cormorants fare better than boobies, which are shallower divers, and pelicans, which mainly fish on the surface.
Majluf also expects high mortality among Peru’s sea lions and fur seals. Only about 20% of the populations of the two species remained by the end of the 1997-98 El Niño, and they did not begin to recover until 2006, when limits on anchovy fishing left more fish in the sea for other wildlife, she says.
Dramatic improvements in communication and technology in Latin America since the 1990s make the current mega-Niño a golden opportunity for other kinds of research as well.
Some scientists have their eyes on the Amazon forest, which is still recovering from major droughts in 2005 and 2010. Covering more than 8 million square kilometers (3.09 million square miles), the Amazon is too large for El Niño to have a uniform impact, so tracking regional effects is important. In addition, the Pacific Ocean’s El Niño affects precipitation over parts of the basin, while sea surface temperatures in the north tropical Atlantic Ocean, off Brazil, affect rainfall in other parts.
Serious large-scale drought is not in the forecast for the basin, though there could be changes in rainfall in some areas, researchers say. Dry spells in areas already hit by drought could make forests more vulnerable to damage when fires set by farmers to clear fields or pastures escape control and burn the edges of woodlands.
Deforestation for agriculture or roads creates more forest edges, which dry out more readily than the denser vegetation deeper inside the forest, making them even more vulnerable to drought and fire in a vicious circle of increasing woodland degradation.
Data gathered last year and this year could shed more light on the “teleconnection” or relationship between ocean temperatures in the Pacific and the Atlantic and how they combine to affect precipitation patterns across the Amazon, Martínez says.
Scientists are also looking at the relationship between El Niño and climate change in a warming world. The El Niño year of 1998 was the warmest on record at the time, and 2015, another El Niño year, was also among the warmest years recorded.
“Each El Niño is different,” Marengo says. “The question is what could happen with El Niño and climate change. There is not agreement among the [climate] models. Some predict more El Niños, while others predict a big event that could last more than two years.”
Scientists are also studying the relationship between El Niño—whose full name, El Niño Southern Oscillation, refers to ocean temperatures that fluctuate on a relatively short term—and the Pacific Decadal Oscillation, during which the ocean temperature fluctuations occur over several decades.
A network of monitoring stations was set up in the Pacific Ocean after the 1982-83 El Niño and expanded after the 1997-98 event to track sea surface temperatures, wind and other data. That information is helping scientists to explore the connections between climate and weather.
But more research is needed to relate those data to impacts around the region, Martínez and Marengo say. There is still a shortage of scientific studies, especially in critical countries such as Peru and Ecuador, which bear the brunt of the warm currents in El Niño years.
And there is the question of what comes next. El Niño conditions will continue for several more months, and it is still too early to tell whether it will be followed by cooler but stable temperatures, or by a La Niña.
- Barbara Fraser