Caldwell was the internationally acclaimed author or coauthor of fifteen books and more than 250 scholarly articles, which may be found in at least 19 different languages.

[1] He served on many boards and advisory committees, as a consultant on environmental policy issues worldwide, and received numerous honors and awards.

By the time of his retirement, further appointments, research and lecture tours and vacations had enabled him to visit nearly one hundred countries around the world as well as every state in the union.

Although not a natural scientist, as part of his work towards establishing interdisciplinary study in universities and achieving a greater merging of the two worlds of science and public policy, he became deeply involved in national and international environmental affairs and worked closely with several important scientific bodies serving, among many appointments, on the Sea Grant Program of the National Oceanic and Atmospheric Administration (NOAA), the first Environmental Advisory Board of the United States Army Corps of Engineers, the Pacific Science Congress, the President’s National Commission on Materials Policy, the Science Advisory Board for the Great Lakes of the International Joint Commission, as chair of the first Commission on Environmental Policy, Law and Administration for the International Union for the Conservation of Nature and Natural Resources (IUCN), and as advisor to the UNESCO Man and the Biosphere Program (MAB), and the UNESCO working program for the environmental education and training of engineers.

[4] During the 1960s Caldwell was virtually a lone voice in attempting to establish policies for the environment because such a holistic and interdisciplinary approach to solving environmental problems did not then exist.

[10] In drafting A National Policy on the Environment in 1968[11] as consultant to Senator Henry Jackson, the head of the powerful Senate Interior and Insular Affairs Committee, Caldwell realized that more was needed than a mere a policy statement: an “action-forcing mechanism” would be necessary to secure federal agency compliance with the Act’s requirements.

The origin of the requirement for preparation of an environmental impact statement (EIS) has been attributed to Caldwell,[12][13] whose testimony at the Senate hearing in April 1969 laid the groundwork for inclusion of provisions requiring an evaluation of the effects of all major federal projects significantly affecting the quality of the human environment.

[20] Shortly after his death in 2006, the Caldwell Center for Culture and Ecology was established in Bloomington, IN to provide environmental education for youth and adults.