Columbus' arrival in the Americas sparked the globalization of animals, plants and microbes. A recent book takes a closer look at how items from the New World, such as potatoes, guano and rubber, quickly and radically transformed the rest of the planet.
Tobacco, potatoes and turkeys came to Europe from America. In exchange, Europeans brought wheat, measles and horses. But who ever thinks about earthworms? Yet they, too, were brought to America by Europeans, and hardly with fewer consequences than those of other, more famous immigrants.
Extinct in large parts of North America since the Ice Age, earthworms began spreading there once again following Christopher Columbus' voyage. Wherever this species appeared in American forests, it changed the landscape, aerating the soil, breaking down fallen foliage and accelerating erosion and nutrient exchange. Earthworms make it easier for some plants to grow, while robbing others of habitat. They take away living space from other bugs, while providing a new source of food for some birds.