primary productivity and support more than two-thirds of the identified species of vascular plants and more than two-thirds of the planet'S total biodiversity. It is in these tropical regions that the cumulative impacts of large-scale dams will most profoundly affect humanity. McCully has written a superbly detailed and well-crafted account of the ecology, economics, and politics of large dams. There are many good reasons to read this book and to carefully reflect on the story it tells. McCully is no doomsday philoso-