Global climate change challenges ecologists to synthesize what we know to solve a problem with deep historical roots in our discipline. In ecology, the question, "How do terrestrial ecosystems interact with the other earth systems to produce planetary change?" has sufficient depth to be the focal challenge. This central question is sharpened further as the changes that we may be manifesting upon our planet's systems of land, sea, air and ice can have potential consequences for the future of human civilization. This book provides the depth of the history of global ecology and reviews the breadth of the ideas being studied today. Each chapter starts with a brief narrative about a scientist whose work traces forward into today's issues in global ecosystems. The discussions are framed in a growing realization that we may be altering the way our planet functions almost before we have gained the necessary knowledge of how it works at all.