It's war in many ecosystems around the world as invasive and native species battle for primacy. Facing the increased exchange of ship ballast water among worldwide ports, biologists are grappling with a rate and scale of alien takeovers unprecedented in history. In this Bio Bulletin, see the mussels and crayfish that are stressing the vast freshwater network of the Great Lakes region, and learn what researchers are doing to give native populations a leg up.
