The presence of ENSO Events in South America is felt in two ways: a) through its <I>effects</I> on both the atmosphere and ocean systems, and b) through its <I>impacts</I> on natural ecosystems (both marine and terrestrial) and on societal and economical sectors (like fisheries, health, and agriculture). <P style="line-height: 20px;"> The main effects of El Ni&#241;o/La Ni&#241;a are: Increment/Decrement of sea surface temperature and salinity, Increment/Decrement of sea level and wave activity, Increment/Decrement of air temperature and amount of ultra violet radiation reaching the surface of the earth, and Changes in the rainfall and evaporation patterns. <P style="line-height: 20px;"> It is not easy to make an "average" pattern of ENSO impacts for a variety of reasons: the impacts depend greatly of factors like geographical extent and position of the oceanic anomalies, and intensity and timing of the anomalies; also the influence of social, economic and political structures determines whether climate anomalies caused by ENSO in a particular region will lead to severe societal and economical impacts. <P style="line-height: 20px;"> The scientific community also plays a potential role in the extent of the impacts that ENSO can produce, if scientists can provide information on the impact of the presence of ENSO by identifying and focusing on its precursors, intervention could be taken early enough. There is however, something to be said against that: information can be misleading, target inappropriate at-risk groups, or generate a false sense of security.