Humboldt's American expedition

In June 1799 the Prussian naturalist Alexander von Humboldt and the French botanist Aime Bonpland sailed from Spain, with the permission of King Charles IV, to explore the Spanish colonies in America. Over five years they traveled through Venezuela, along the Orinoco River, and through Cuba, Colombia, Ecuador, Peru and Mexico, before ending in the United States, where Humboldt met President Jefferson. They measured temperature, air pressure, magnetism and altitude with a trunk of instruments, and gathered a vast collection of plants, animals and rocks.¹²

Linnaeus had given naturalists a way to name and sort species, and Cook's voyages had shown the value of carrying instruments and scientists around the world. Humboldt asked a different question: how do things connect? In 1802 he climbed Chimborazo in Ecuador, then thought the highest mountain in the world, and noticed that plant zones from the foot to the summit resembled the zones from the tropics to the poles. His 1807 diagram of vegetation by altitude, the Naturgemalde, showed climate, height and geography together. He also saw that people alter nature: he linked the shrinking of Lake Valencia in Venezuela to deforestation and irrigation, and he condemned slavery in the colonies.²³

Humboldt spent the next decades publishing about thirty volumes of results and his Personal Narrative, then the five-volume Kosmos from 1845. Charles Darwin carried the Personal Narrative on the Beagle and said it inspired his own voyage. Humboldt's picture of nature as an interconnected web influenced later ecologists, geographers and writers such as Henry David Thoreau and John Muir.¹²