Ecosystem health offers a fresh perspective on the management of natural resources and the environment. While some of the root concepts can surely be traced back to Aldo Leopold and even earlier, it is only in the recent decade that a substantial body of work has emerged on this topic. There is no question that a novel approach which is by its nature cross- disciplinary, bridging the health and biological sciences, will initially raise a number of questions particularly pertaining to the use of metaphors and the validity of the analogy. This volume however goes beyond merely the philosophical dimensions of the subject by covering a number of case studies which have given rise to the development of promising quantitative methods for diagnosis and rehabilitation of ecosystems under stress. The focus of most studies is on regional ecosystems i.e. ecosystems of large scale. As such, the methods and approaches should have wide appeal to government agencies charged with the responsibility of sustainable development of regional ecosystems and natural resources. Health is one of those difficult concepts that everyone thinks they can define, until they come to try. We all have personal knowledge about health and illness and this makes the ecosystem analogy so potentially powerful. Yet it is also clear that the uncritical application of the concept could lead to overly simplistic approaches to analysis and management of ecosystem health.