This current drives the surface water away from the equator, and draws water up from below. Winds also cause warm surface water to accumulate on the western side of the Pacific. As a result, nutrient-rich water rises from deeper levels to replace the surface water that has drifted away. These nutrients are responsible for supporting the large fish population commonly found in these areas.
Fish then die off or move elsewhere, such as southward off Chile or north toward California.
One of the main areas of the globe most seriously affected is Australia. The fluctuations of climate and other environmental effects also operate on a large scale. The 1982-1983 severely affected over half the continent, an area 25 times the size of England and Wales. The lack of major mountain ranges inland also contributes to the large scale fluctuations. Many Australian droughts, and extensive wet periods, tend to last about 12 months.