Robert Haxall “Bobby” Johnson, a conservationist and real estate appraiser, died of chronic obstructive pulmonary disease complications July 30 at his Brooklandville home. He was 76.

Born in Baltimore, he was the son of Josephine Dixon Johnson, a nurse, and Dr. Robert Wilkinson Johnson III, a plastic surgeon.

As a child, he was fascinated by the animals he found on his family’s Brooklandville property.

He went on to graduate from Gilman School and earned a mathematics degree from Harvard University in Cambridge, Massachusetts. He also pursued a doctorate in herpetology from the Johns Hopkins University and taught briefly at Case Western Reserve University in Cleveland, Ohio.

Mr. Johnson became a real estate appraiser and worked for the old Colliers Pinkard and AGM Financial Services.

“Bobby was not simply an appraiser, but a professional who brought an extremely unique analytic capability to the way he tackled assignments that distinguished him within the profession,” said Walter D. “Wally” Pinkard, a friend.

A colleague at AGM, Brian LaChapelle, said: “Bob could read an inches-thick appraisal report as if he were a professor. He was a mathematician first but he was also keen on grammar.”

Mr. Johnson became interested in the ecology of the Jones Falls Valley and the streams within it.

“My father often wore paint-covered clothing,” said a daughter, Jesse Randol. “He was a passionate naturalist, conservationist and lover of learning.

Mr. Johnson joined the education department at the Maryland Zoo in Baltimore and was a co-founder of the Irvine Nature Center in Owings Mills.

“Bobby was a force for nature before it was fashionable,” said Brooks Paternotte, the Irvine Center’s director. “He saw the importance of watersheds and how they were important to the ecosystems and health of community.”

He was a past president of the Jones Falls Watershed Association and worked to create Blue Water Baltimore from other smaller organizations and sat on its board.

“That exercise of merging the organizations into Blue Water Baltimore took patience and was no small feat,” said Alice Volpitta, Baltimore Harbor Waterkeeper for Blue Water Baltimore. “Bobby was funny, hilarious and kind. The first time I met him in 2014 Bobby was the first one to make me feel like I was at home again. He made me feel welcome at Blue Water.

“It was his dream to have Blue Water Baltimore exist in the first place,” said Ms. Volpitta.

“My father loved sharing the wonder of the natural world with anyone who would listen, hosting frog catching sessions, night walks and nature hikes identifying local trees and plants by their common and scientific names,” said a daughter, Jesse Randol.

A memorial service will be held at 10 a.m. Sept. 14 in the Vollmer Center at Cylburn Arboretum at 4915 Greenspring Avenue.

Survivors include two daughters, Jesse Randol, of Bedford, New York, and Katherine Johnson, of Timonium; three sons, Marshall Johnson, of Philadelphia, Nicholas Johnson, of Brooklandville, and Thomas Johnson, of Baltimore; two brothers, Pearce Johnson, of Charlottesville, Virginia, and Brock Johnson, of Brooklandville; a sister, Jody Johnson, of Brooklandville; and four grandchildren.