We’ve all seen the images. Monsoons and floods and fierce winds that claim hundreds of lives and destroy thousands of homes — the disastrous legacy of El Niño.
But scientists around the world are collecting evidence showing that what we see is only a small part of what we get. Like the tip of the proverbial iceberg, the atmospheric disruptions brought on by the periodic warming of the waters of the central Pacific Ocean bring far more serious consequences than what we see on the surface.
Feared for decades by fishermen of Peru because of its devastating impact on fish populations along their coast, El Niño escaped close scrutiny by scientists until relatively recently. But in 1982-83 an estimated 85 percent of the sea birds in Peru were killed and horrendous storms raged along the coast of California — that really caught their attention.
That was followed by several lesser El Niño events, which occur every 3.7 years, but the 1997-98 El Niño moved the phenomenon onto center stage. Scientists knew well in advance that it was coming, and that it would be really big. Their research, much of which is still being analyzed, has led to some startling conclusions.
Scientists at several institutions, including Cornell University, have uncovered compelling evidence that the number of cholera cases in Bangladesh rises dramatically almost precisely 11 months after the waters of the equatorial Pacific begin to warm thousands of miles away.
Experts have long suspected they would find some upsurge in cholera because warmer waters enhance the growth of a pathogenic microorganism, Vibrio cholerae, that carries the disease. One of the leaders in the field is Rita Colwell, professor of cell and molecular biology at the University of Maryland and director of the National Science Foundation.
But a direct connection eluded them until the researchers came across a hospital in Bangladesh, one of the poorest and most densely populated nations on the planet, that had tested all incoming patients for cholera since January of 1980. That was just the data needed by Stephen P. Ellner, a biomathematician at Cornell.
Ellner created a computer model, into which he pumped all kinds of data, such as flooding from the snowmelt in the Himalayas, to see if a pattern emerged that could be linked to El Niño. What they found was quite startling. The number of cholera cases at the hospital peaked every 3.7 years, exactly the same frequency as the occurrences of El Niño.
But there was a twist. The peaks came 11 months after the beginning of the El Niño.
Further research offered tantalizing clues. It takes six months for the warmer waters to reach the shores of Bangladesh, and it takes another five months for the population of the deadly microorganisms to peak in the warmer waters. Bingo. That’s 11 months, matching the increase in the level of the disease precisely with the beginning of the El Niño.
As the researchers themselves point out, that’s only one test, and similar results will have to be found in other areas before the findings can be fully embraced by the scientific community. But it suggests very strongly that there is a link between El Niño and cholera, making the phenomenon far more deadly than had been thought.
The finding is particularly disturbing because many scientists believe El Niño’s intensity will get even worse if the planet continues its current warming trend.
Problems Pile On
Incidentally, Bangladesh seems to get the worst of everything these days. Bangladesh, much of which is barely above sea level, is frequently devastated by monsoons, especially during an El Niño. And the World Health Organization warned recently that the country’s drinking water is so contaminated with naturally-occurring arsenic that Bangladesh is “grappling with the largest mass poisoning of a population in history.”
The organization warned in a recent report that 35 to 77 million people of the country’s total population of 125 million are at risk from arsenic in their drinking water, which can cause cancer and other deadly diseases. Allan H. Smith, professor of epidemiology at the University of California at Berkeley and author of the organization’s report, labeled it a potential epidemic that could make disasters like the meltdown of the Chernobyl nuclear plant pale by comparison.
So Bangladesh has more to worry about than El Niño, as deadly as that may be.
Meanwhile, other researchers are finding that El Niño strikes right at the heart of the marine ecosystem, which supplies so much of the world with its basic food resources.
Scientists at Scripps Institution of Oceanography at the University of California, San Diego, have confirmed what many expected, that the warmer waters of El Niño reduce the population of phytoplankton, the tiny plant-like organisms that form the bottom of the food chain upon which all other marine organisms depend.
Thinning a Food Source
By analyzing high-resolution satellite images, Mati Kahru and Greg Mitchell of Scripps found the warmer waters of an El Niño, which are lower in nutrients, severely reduces the amount of phytoplankton. It also causes the resource to be distributed more evenly, wiping out the concentrations upon which so many different types of fish feed.
Deprived of that resource, millions of fish move north or south in search of food, where many of them die because the water is too cold for them to survive, or they starve.
The forced migration can also have a ripple effect. Scientists have found that mackerel migrated farther north than usual, feeding on juvenile salmon and thus further depleting this important and troubled resource.
Other scientists have found evidence of the ripple effect even in sea birds. Bird feces are rich in guano, a natural fertilizer that is essential for agriculture. During a strong El Niño, many sea birds migrate to the wrong areas and die, but the scale of this problem is not yet understood.
There is also much evidence that El Niño is contributing to the death of coral reefs around the world, depriving marine creatures of a nutrient-rich habitat. Pollution and scavenging also play a role in this, as in many other cases of resource destruction.
The growing body of evidence doesn’t mean the world is coming to an end. But it does remind us, once again, of the complexity of the world in which we live.
We can’t shut off El Niño. So we better learn how to live with it.
Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.