Who was Alexander von Humboldt?
Alexander von Humboldt (1769–1859) was a Prussian naturalist and explorer who established the idea that nature is an interconnected system — a conception so thoroughly absorbed into modern thinking that its origin is forgotten.
What he did. Between 1799 and 1804 he travelled through Latin America, covering enormous distances and taking measurements obsessively: temperature, pressure, altitude, magnetism, humidity, the blueness of the sky, the composition of rocks and the distribution of plants.
The insight that mattered. Climbing Chimborazo in the Andes, he observed that plant communities changed with altitude in the same sequence as they change with latitude — an ascent through vegetation zones mirroring a journey from the equator to the poles. From this he grasped that climate, geology, vegetation and animal life form a single interconnected system, and that this system behaves comparably in comparable conditions anywhere on Earth.
He invented the isotherm — lines joining points of equal temperature — and the practice of representing global patterns on maps, which is the ancestor of essentially all climate visualisation.
He described human-caused environmental damage remarkably early. Observing the effects of colonial plantation agriculture around Lake Valencia in Venezuela, he identified deforestation as causing falling water levels, soil erosion and local climatic change — and warned about the consequences of the human species interfering with the climate, in terms that read as startlingly modern.
His influence. Cosmos, his attempt to describe the entire physical universe as a unified whole, was an enormous popular success. He was, by a considerable margin, the most famous scientist of his era.
Darwin carried his account on the Beagle and described him as having influenced him more than anyone; Darwin said he would not have joined the voyage or conceived his work without reading Humboldt.
He is commemorated more widely than almost anyone — in ocean currents, mountain ranges, towns, a penguin, a squid, a sea, and lunar features.
Why he faded from public memory is debated: anti-German sentiment following two world wars is frequently cited, along with the fragmentation of science into specialisms, which left no discipline claiming a man who worked across all of them.
He opposed slavery and colonialism explicitly, which was unusual among his contemporaries and cost him support.