Zebra mussels, for example, were not the only, or even the greatest, threat to native clams in the Great Lakes. Besides disrupting the local ecosystems, the mussels filtered water and became a new source of food for native fish and fowl. One surprising statistic is that since the introduction of European species to the Americas four hundred years ago, biodiversity has actually increased by 18 percent. As Shah puts it, “Nature transgresses borders all the time.”
