The amazing diversity of life on the Galapagos Islands is largely due to a phenomenon known as the Humboldt Current. Ocean currents are caused and affected by many different factors, including the gravitational pull of the moon, the earth's rotation, underwater geography, salinity, wind and water temperature. These currents are very important to life on land, as they can affect climate, shipping, fishing and life such as birds or other species that live off of marine animals and fish.

Beginning in Antarctic waters, the Humboldt Current runs north and west along the western coast of South America, bringing cool water from the south to the coasts of Chile, Peru and Ecuador. When it reaches the equator, it takes a sharp westward turn due to the Coriolis effect. It then passes through the Galapagos Islands, bringing with it rich nutrients that have been upwelled in southern seas. These nutrients feed plants and plankton, which in turn form the base of the food chain.

Many visitors to the Galapagos are surprised by the cool water: this is due to the Humboldt Current bringing in cool water. From June to October, the southeast trade winds bring about an increase of the current, making the water in the islands cooler. From November to May, the trade winds are reduced, and although the Humboldt still passes through Galapagos, it does not do so with as much force and the waters around the islands is warmer. The decreased current also allows warmer water from off of Central America to reach the archipelago in these months.

The Humboldt is also responsible for Galapagos' two main seasons: the hot season, which runs from November to May, and the cooler, dry season from June to October. The cooler waters of the Humboldt current are less likely to evaporate and form clouds, which results in less rain.

The most visible effect of the Humboldt Current in Galapagos is the abundant life, both marine and terrestrial. All life in Galapagos is ultimately dependant on the Humboldt current and the nutrients it brings with it every year. Some animals, such as the endemic Galapagos penguin, rely at least partly on the cool water to survive, while others, such as the Galapagos sea lion, feast on the fish that live off of the nutrients brought in from the south. The Humboldt is the most productive marine ecosystem in the world, and is responsible for approximately 20% of the world's fish catch, most of which are species live relatively close to the surface such as sardines and mackerel. The booming fisheries of Peru and Chile rely heavily on the Humboldt Current.

The Humboldt Current is disrupted during el Niño years, as it affects air pressure, decreases trade winds and causes warmer water to move east from the Western Pacific. With the Humboldt weakened, fish move elsewhere to feed and birds, sea lions and other Galapagos animals starve. A typical el Niño year in Galapagos is marked by significantly less wildlife than other years.

The Humboldt Current is named for Prussian scientist, explorer, naturalist and writer Alexander Von Humboldt, who visited Latin America from 1799 to 1804. His observations greatly advanced science at the time and his career was celebrated in Europe. His journeys inspired Charles Darwin, who would make the islands famous when he linked them to his Theory of Evolution.