Andrew L. Johnson, 83, of Chadds Ford, a prominent conservationist who helped establish the Brandywine Conservancy and Museum of Art, the Natural Lands Trust, and the North American Land Trust, died Saturday, June 19, after a brief illness.

During a career that spanned decades, Mr. Johnson served as executive director of the Brandywine Conservancy during its formative years from 1970 to 1976, during which he oversaw the renovation of the old mill building that became the Brandywine River Museum.

He was president of the Natural Lands Trust from 1979 to 1988 and went on, in 1992, to found the North American Land Trust. He served as its president until he retired in 2015.

The nonprofit NALT, a Chadds Ford land conservation group that has worked on more than 550 projects in 23 states involving more than 136,000 acres of protected land, was Mr. Johnson’s crowning professional achievement, said Steven Carter, the group’s current president.

“He was a conservation pioneer. He was really on the cutting edge of working with every type of entity out there — government, private parties, other land conservation organizations — trying to put together the best plan for a piece of property to protect the natural resources,” said Carter, who called Mr. Johnson a mentor.

In 1992, after serving as a conservation consultant in New York, Mr. Johnson founded NALT with a mission to permanently conserve and manage open spaces with natural habitats, or agricultural, historic, or scenic value, the organization said in a statement.

“The conservation community has lost a leader, a visionary and a friend,” said Carter.

Mr. Johnson was born July 31, 1937, in Chicago. Because his grandfather was a minister, his family expected him to enter into the ministry, but he found another calling at an early age.

In 1953, while attending a Boy Scout Jamboree in Irvine, Calif., the then-16-year-old encountered organizations dedicated to natural resources and conservation, which became his passion. He forged a lifelong belief in permanent conservation of open spaces along with carefully planned, limited development, according to the NALT. These development projects at times involve tax benefits for property owners, which in some cases has drawn criticism and legal scrutiny.

Mr. Johnson attended Grinnell College in Grinnell, Iowa, where he graduated with a bachelor’s degree in ecology science, and earned a master’s degree in forest science from Yale School of Forestry and Environmental Sciences in New Haven, Conn.

Before beginning his career as a land conservationist, Mr. Johnson served in the Air Force, during which he was stationed in San Antonio, Texas, and Chaumont, France, and was awarded the Air Force Commendation medal and rose to the rank of captain.

After working at the Missouri Botanical Garden in St. Louis, Mr. Johnson moved his young family to Chadds Ford to accept a position at the Tri-County Conservancy of the Brandywine, which is now the Brandywine Conservancy and Museum of Art.

Mr. Johnson’s passion for protecting natural resources and his many years of conservation experience led him to establish NALT.

Andy Pitz, who was hired by Mr. Johnson to work as the director of planning at Natural Lands Trusts in 1986, said he was an innovative thinker when it came to protecting land.

“He was kind of a character and very funny,” Pitz added. “He had a keen sense of business and what would motivate people to do the right, charitable thing. He saw things from a different angle and would come up with creative solutions.”

Mr. Johnson is survived by his wife of 53 years, Elizabeth; his daughter, Kristina Johnson; his son, Eric; two grandchildren; and a sister.

The family is planning a private memorial service. In lieu of flowers, donations may be made to the North American Land Trust, P.O. Box 467, Chadds Ford, Pa. 19317.