Jack S. McCormick, 50, an ecologist, author and president of an environmental consulting firm, died Monday at his home in Bethesda following a heart attack.

Before coming to this area about 1976, Mr. McCormick had worked as a botonist and naturalist in Indiana and consultant on ecology to the American Museum of Natural History in New York City, where he designed the museum's hall of North American forests.

He also taught ecology at Ohio State University and the University of Pennsylvania and was chairman of the department of ecology and land management at the Academy of Natural Sciences of Philadelphia before establishing his own consulting firm in 1971.

The firm, Jack McCormick & Associates Inc. of Devon, Pa., was acquired by Wapora Inc. of Chevy Chase, Md., in 1976. Mr. McCormick remained as president of the former company while serving on the staff of Wapora.

Mr. McCormick was born in Indianapolis. In 1951, he graduated with a bachelor's degree in botany from Butler University there, then earned a doctorate in ecology from Rutgers University in New Jersey in 1955.

He was the author of several books, including "The Life of the Forest." He also wrote more than 100 scientific papers in his field and wrote or was the coauthor of environmental reports on the wetlands of Maryland, the New Jersey coastal zone and the Hackensack meadowlands of New Jersey. He also wrote a study of the Alaska wetlands for the Army Corps of Engineers.

Mr. McCormick was a member of the American Association for the Advancement of Science, the Ecological Society of America, and the Torrey Botany Club.

He is survived by his wife, the former Janet Pickens, of the home in Bethesda; a son, James R., of Berwyn, Pa.; a daughter, Wendy Lynn, of Chadds Ford, Pa., and his parents, James A. and Betty Sovern McCormick, of Indianapolis.