Lynton Keith Caldwell, who helped shape the nation’s environmental policy requiring environmental impact studies for major projects, died Tuesday at his Bloomington, Ind., home. He was 92.

Caldwell, a professor emeritus at Indiana University, helped write the National Environmental Policy Act of 1969. His draft resolution, much of which was incorporated into the act, required environmental impact studies for all major federal projects that would significantly affect the environment.

“At the time, that was a novel idea,” said Christian Freitag, executive director of the Sycamore Land Trust, a land preservation group that Caldwell helped create.

Caldwell studied history, government and political science at Harvard University and the University of Chicago in the late 1930s and early 1940s. He taught at Syracuse University, the University of California at Berkeley and IU.

In the early 1960s, Caldwell began studying how humans relate to their environment a “revelation,” he later called it which became his life’s work.

He was a key player in creating IU’s School of Public and Environmental Affairs.

Astrid Merget, dean of the school, said Caldwell’s passion for his work never faded.

“He was a conscience,” Merget said. “He was a relentless watchdog … His mind was always forward-looking.”

Caldwell is survived by his wife of 65 years, Helen, and two children, Edwin Lee Caldwell, of Bloomington, and Elaine Caldwell Emmi, of Salt Lake City.

Emmi said her father made life an adventure.

“What I got from him was a way of looking at the world, and I’ve spent a lot of my life working on environmental policy, too,” she said.