Two key demands are being made of ecology: that the discipline increasingly be a predictive one; and that ecologists be prepared to consider large-scale systems. These systems become simple or complex based on the level and type of explanation required, and a strict and consistent epistemology is needed in light of new insights into the nature of complexity. T.F.H. Allen and Thomas W. Hoekstra argue that complex systems analysis requires ecologists to distinguish models and to recognize that models must invoke a scale and point of view. Toward a Unified Ecology offers a strategy to attain a unity that brings basic ecology to bear on ecological management. Beginning with hierarchy theory as a basic premise, the book goes on to explain that the conventional "levels"--Ecosystems, landscapes, communities, populations, organisms--are not levels in themselves but criteria for observation. The authors assert that the essential character of ecology's subdisciplines is scale-dependent. Putting scale back into systems of well-defined type captures the richness of the connections in the material ecological system. Allen and Hoekstra present a conceptual framework for a more coherent view of ecology, showing how to link the various parts of ecology into a natural whole.