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Mongabay.com is considered a leading source of information on tropical forests by some of the world's top ecologists and conservationists. TROPICAL RAINFORESTS: Disappearing Opportunities

El Niño: A Preview of Global Warming?



In 1997-98, the world got another taste of what global warming might entail. A disruption of the ocean-atmosphere system in the tropical Pacific, El Niño causes worldwide effects in weather with major impacts on agriculture, fisheries, economics, and social conditions.

El Niño, or more accurately, the El Niño-Southern Oscillation effect (ENSO), is characterized by a change in Pacific tradewinds and the warming of the tropical Pacific. Under normal conditions, a strong trade wind blows East to West along the Equator in the Pacific causing a rise of water level of 1.5 to 3 feet (0.5-1 m) in the Western Pacific near Southeast Asia. The difference in water temperature between the East Pacific (the coast of Peru) and West Pacific (the coast of Indonesia) is about 8 degrees Celsius. With El Niño, the winds pushing water to the west weaken and some of the water piled up in the West slumps back to the East. The return of warm water from the East means that less of the nutrient rich cold water usually brought up from the ocean depths along the coast of Peru, is brought to the shallows. The water temperature in the Eastern Pacific increases, further decreasing the Westerly trade winds feeding the El Niño conditions. El Niño is eventually reversed by the return of cooler water brought by a slow moving wave created by El Niño. This wave moves Westward, reflects off Southeast Asia, and returns to cancel out the warmth of the East Pacific. El Niño causes shifts in tropical rainfall which affects wind pattern worldwide, causing abnormalities in weather conditions. These changes in weather are poorly understood and scientists are unable to predict the strength or the exact nature of the effects, but based on the strong El Niño of 1982-83, some of the effects can be expected to include:

South America: Flooding in Peru and Ecuador, drought in the South. In the past, there have been terrible mudslides, made worse by deforestation, in Peru which have caused extensive failures in infrastructure. The falling nutrient levels of the ocean causes anchovy harvests to decrease off the coast of Peru, causing a rise in food prices. Anchovies are an important ingredient in chicken and livestock feed and guano from birds that feed on anchovies is a major source of fertilizer for U.S. farmers. The increased production costs translates to higher grocery store prices in grains, bread, milk, eggs, and meat. Overall, El Niño has a tremendous cost in South America; Peru alone anticipates more than $1.2 billion in damages. El Niño also creates dry conditions in much of the Amazon Basin worsening annual fires set by developers and peasants.
Southeast Asia/West Pacific: Much of the western Pacific was affected by drought conditions, exacerbating serious wildfires in Indonesia that lead to airport closings and hospitalizations. In 1982-83, extensive wildfires in Borneo burned more than 9 million acres (3.6 million ha) of rainforest and croplands. In 1997-98 the fires burned again sending a dense haze over six Asian countries. China, in the midst of its worst drought in 50 years (the Yellow river ran dry in September 1997), can expect drought conditions to worsen resulting in lower grain and cotton yields.
Australia/Papua New Guinea: Drought and fires endangered lives and the grain harvest in Australia. Papua New Guinea suffered a serious drought: rivers and dams dried up, and mining operations ceased. Coffee production fell 50% and bushfires raged out of control destroying other important crops and rainforest. People in the highlands are deserted villages in search of food and hundreds starved to death.
United States: El Niño cost the United States $1.3 billion in 1982-1983, and will probably be even more costly in 1997. California experienced a flurry of powerful storms resulting in flooding and extensive storm damage, but Southern California may be cleansed of some of its smog and blessed with good surfing. El Niño created a lower pressure area off the California coast resulting in the inflow of tropical precipitation. The Eastern United States probably can expect a wet winter, but a decline in hurricanes. The midwest could experience a warm winter and the South may have a very wet winter.
Africa: El Niño is expected to cause drought and famine in Southern and Western Africa. Agricultural production in South Africa is anticipated to decline creating economic crisis and social unrest.
Ecological Effects: El Niño has a poorly studied, but tremendous and obvious impact on natural systems. In 1982-83, low tides and the movement of warm water to the east caused severe bleaching and death of 70 to 95 percent of the corals from Colombia to Costa Rica. In 1998 Greenpeace and the Great Barrier Reef Marine Authority reported 25% of the coral on the Great Barrier Reef of Australia was severely bleached, while 60% of the reef was affected by bleaching. Researchers have observed changes in migratory patterns of birds, whales, and fish, and people in Washington are catching marlin and other tropical fish for the first time in recorded history. The dry conditions in the tropics, combined with forest degradation and fragmentation, are tinder for giant forest fires.

While evidence of El Niño/La Niña events extends back thousands of years, many scientists believe that El Niño may be attributable to global warming, though the connection is still elusive. It is clear though, that five out of the first seven years of the 1990s have been classified as having El Niño conditions, whereas prior El Niño events happened every 3 to 7 years. It is possible that the increased thermal energy in the atmospheric system causes the normal variations of the El Niño phenomena to be exaggerated and accelerated.


Continued: Extinction


Other pages in this section:

Consequences of Deforestation
Erosion
Loss of Renewable Resources
Atmospheric Role
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References
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Loss of Species, Disease
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