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1. Fish in a trap
In normal times, along the South-American coasts cold-water masses are observed rising up
from the nutrient-salt rich ocean depths: this effect is upwelling. During El Niño episodes, the
warm waters which then bathe the South-American coasts block this rise of nutrients which are
the staple food of plankton. The fish - sardines, herring and pilchards - are deprived of their food
source. They leave these areas and migrate further South seeking cooler waters. Fishing stocks
and catches consequently plummet.
A phenomenon known as “miracle catches” also contributes to exhaustion of the fish stock. It arises as
the El Niño event begins: masses of fish accumulate, trapped in residual pockets of cold water, giving
fishermen some bumper catches.
2. Health effects
In regions whose climate has altered, El Niño-associated variations in temperature and precipitation could
favour the spread of infectious diseases, especially those transmitted by mosquitoes (malaria, dengue, yellow fever)
or rodents (hantavirus).
A correlation has been found between peaks of malaria incidence and El Niño episodes in certain regions
of South-East Asia and East Africa, dengue fever in Thailand and cholera in South America, Bangladesh and
West Africa. For example, flooding in normally dry regions often provokes epidemics of malaria or cholera.
e past 50
d more frequent over th
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El Niño,
in South America.
causing glacier melting
years, is
3. Increased glacier melting
The central Andes are experiencing significant El Niño-induced decrease in
precipitation (from 10 to 25%) and a noticeable rise in temperatures. Fresh snowfalls
are less abundant, and the glacier albedo (the ability of their surface to reflect solar
radiation) is falling. The energy the ice absorbs is therefore greater and glacier
melting increases.
The socio-economic impact of El Niño event of 1997-1998 in figures
More than 110 million people affected in the world. More than 6 million people displaced
following destruction of housing, public facilities, transport and communications by storms
24,000 people victims of fierce winds,
34 billion dollars of direct economic losses.
More than
floods or tidal waves. More than
After L’avenir de l’environnement mondial GEO-3, PNUE, 2002.
es are hit more severely by El Niño’s
People who live in the poorest countri
th are
populations of the countries of the Sou
repercussions than others. The coastal
urces and
r strong dependence on natural reso
particularly vulnerable, owing to thei
ical
ate variability and extreme meteorolog
their limited capacity to face up to clim
170 °
160 °
150 °
events.