Humboldt’s hog-nosed skunk, the Humboldt penguin, the Humboldt squid, and more than a hundred other animal species; Humboldt’s Lily, Humboldt’s Schomburgkia, and three hundred other plant species; the minerals Humboldtit, Humboldtilith, and Humboldtin; Humboldt Limestone, Humboldt Oolite, the Humboldt Formation, the Humboldt Current; Humboldt Redwoods State Park, Humboldt-Toiyabe National Forest, Parque Nacional Alejandro de Humboldt; Mont Humboldt, Humboldt Mountain, Humboldt Peak, and Humboldt ranges in China, South Africa, and Antarctica; Humboldt Falls, Humboldt Glacier, Humboldt Bay, the Humboldt River, the Humboldt Sink, the Humboldt Salt Marsh; four Humboldt counties and thirteen Humboldt towns in North America alone, the Humboldt crater and Mare Humboldtianum on the moon, and asteroid 54 Alexandra, orbiting the sun.

The Prussian naturalist Alexander von Humboldt (1769–1859) is all around us. Yet he is invisible. “Alexander von Humboldt has been largely forgotten in the English-speaking world,” writes Andrea Wulf in her thrilling new biography. “It is almost as though his ideas have become so manifest that the man behind them has disappeared.” Wulf’s book is as much a history of those ideas as it is of the man. The man may be lost but his ideas have never been more alive.

Humboldt’s legacy appeared certain at the time of his death, when he was the most famous scientist in the world. His funeral in Berlin was the grandest ever accorded to a private German individual; a procession of tens of thousands of mourners followed for a mile behind his hearse, pulled by the king’s horses. American newspapers eulogized him as the “most remarkable man ever born” and lamented the end of the “age of Humboldt.” His portrait hung on the walls of state buildings from London to Bangkok.

A decade later, on the centennial of Humboldt’s birth, parades, concerts, and firework shows were held in Moscow, Alexandria, Buenos Aires, Mexico City, Melbourne, and dozens of American cities. Fifteen thousand marched in Syracuse, President Ulysses Grant joined a huge celebration in Pittsburgh, and 25,000 assembled in Central Park, in the midst of a euphoric citywide bonanza. The New York Times devoted its entire front page to the global festivities.

Times changed. Anti-German sentiment after World War I, the specialization and Balkanization of the sciences, and the passage of time conspired to dilute Humboldt’s public standing, particularly in the United States. He was eclipsed by devoted disciples—among them Charles Lyell, Charles Darwin, Henry David Thoreau, George Perkins Marsh, Ernst Haeckel, and John Muir—who developed his insights in new ways. But times have changed again. In our Anthropocene age Humboldt’s theories read like prophecy. More important, they offer wisdom about the way forward. It is impossible to read The Invention of Nature without contracting Humboldt fever. Wulf makes Humboldtians of us all.

Humboldt was born during the era in which human beings…