With increases in the number of people travelling, the speed and methods of travel, the types and volume of trade, the ability to move living plants and animals so that more of them survive the journey, and the different modes of transport for hitch-hiking organisms, invasive species have become a global concern. Although there are many ways in which species may invade, this book focuses on ballast water discharge by cargo ships as one of the more significant mechanisms for biotic invasion of coastal and estuarine habitats as well as inland navigable waters. This book provides background on various approaches to ballast water management and reviews currents laws and programs.