former student Patrick Kangas. Kangas and his student, David Blersch, made significant contributions to the design of the waste water recycling system on the station. Odum's students have furthered his work at institutions around the world, most notably Mark Brown at the University of Florida, David Tilley and Patrick Kangas at the University of Maryland, Daniel Campbell at the United States Environmental Protection Agency, Enrique Ortega at the UNICAMP in Brazil, and Sergio Ulgiati at the University of Siena. Work done at these institutions continues to evolve and propagate the Odum's concept of emergy. His former students Bill Mitsch, Robert Costanza, and Karin Limburg are some former students who have been recognized internationally for their contributions to ecological engineering, ecological economics, ecosystem science, wetland ecology, estuarine ecology, ecological modeling, and related fields. Work: an overview Odum left a large legacy in many fields associated with ecology, systems, and energetics. He studied ecosystems all over the world, and pioneered the study of several areas, some of which are now distinct fields of research. According to Hall (1995, p.ix), Odum published one of the first significant papers in each of the following areas: Ecological modeling (Odum 1960a) Ecological engineering (Odum et al. 1963) Ecological economics (Odum 1971) Estuarine ecology (Odum and Hoskins 1958) Tropical ecosystems ecology (Odum and Pidgeon 1970) General systems theory Odum's contributions to these and other areas are summarized below. Odum also wrote on radiation ecology, systems ecology, unified science, and the microcosm. He was one of the first to discuss the use of ecosystems for life-support function in space travel. Some have suggested that Odum was technocratic in orientation, while others believe that he sided with those calling for "new values". Ecological modeling A new integrative approach in ecology In his 1950 Ph.D. thesis, Odum gave a novel definition of ecology as the study of large entities (ecosystems) at the "natural level of integration". In the traditional role of an ecologist, one of Odum's doctoral aims was to recognize and classify large cyclic entities (ecosystems). However, another one of his aims was to make predictive generalizations about ecosystems, such as the whole world for example. For Odum, as a large entity, the world constituted a revolving cycle with high stability. It was the presence of stability, which Odum believed enabled him to talk about the teleology of such systems. While he was writing his thesis, Odum felt that