The emergence of modern agriculture demonstrates this dramatically. It all began with discoveries by two Germans. World traveler Alexander von Humboldt was the first to take an interest in the indigenous people who broke stinking chunks off the rocky cliffs where birds perched along the Peruvian coast. Chemist Justus von Liebig then recognized that the resulting powder, thanks to its high nitrogen and phosphorus content, made an excellent fertilizer.
Guano, as the local people called this substance made of hardened bird droppings, soon became one of the most significant imported products in the up-and-coming continent of Europe. Mann calculates that the total value of natural fertilizer exports from Peru would equal $15 billion (€11 billion) in today's terms.
This time, the Chinese were among the ones who suffered, forced to labor amid the ammonia stench of the guano. A total of around 100,000 Chinese people were enticed to far-away South America under the lure of false promises.
Just as Europe's agriculture became dependent on a natural product from South America, so did its industry, as rubber -- whether in the form of car tires, cable insulation or sealing rings for pipes -- became an indispensable part of modern technology.
Tapped from the bark of the rubber tree, natural rubber was shipped across the Atlantic in ever greater quantities. No matter how rapidly Brazil's rubber exports increased, demand grew even more quickly and prices continued to climb.
But a sudden end to the boom came when South American leaf blight, a fungus, decimated nearly all of South America's rubber plantations. Thailand, Indonesia and Malaysia now became rubber-producing superpowers, replacing Brazil, Venezuela and Suriname. This was possible because of a British man named Henry Wickham, who became something of a hero of the "Columbian Exchange" when he smuggled Brazilian rubber tree seeds out of the country in 1876.
Just how easily a second Wickham could come along -- this time spreading not the rubber tree, but its leaf blight, around the world -- became clear to Mann during a research trip, when he found himself standing in the middle of an Asian rubber plantation, wearing the same boots he had worn just months before on a tromp through the Brazilian rainforest. What if a few spores of the fungus were still stuck to his boots?
At some point the Columbian Exchange will come full circle, Mann writes, and then the world will have another problem.
Translated from the German by Ella Ornstein