Thomas G. Siccama, a professor in the Practice of Forest Ecology at the Yale School of Forestry & Environmental Studies (F&ES) for 40 years, died on Friday, Oct. 3, while in hospice care. He was 78.

Siccama joined the Yale faculty in 1967. A prominent field naturalist, he published over 120 papers and was considered an expert on forest ecosystems of the northeastern U.S.

For many F&ES students, Siccama’s lessons in the field solidified their appreciation and understanding of the natural world. His crash course on plant identification in the School’s summer orientation was an essential part of the F&ES experience. He received the School’s top teaching and advising award four times.

“Tom was someone who was extremely passionate about what did,” F&ES Communications Director said Kevin Dennehy said. “He loved the natural world and always saw opportunities to teach and to change the way people see the world.”

Siccama studied terrestrial ecosystems, specifically how trace elements cycle through soils. From the start of his Yale career, Siccama was involved with the Hubbard Brook Ecosystem Study, a major research project based in the White Mountain National Forest of New Hampshire. The research ultimately lead to the federal government banning lead gasoline.

Siccama was born in Rahway, N.J. He graduated from the University of Vermont, from which he earned a B.S., M.S., and Ph.D. He is survived by his wife, daughter, granddaughter, son-in-law, sister-in-law, and brother-in-law.