Fame
Rachel Carson, Edward Abbey, Jane Goodall, John Muir, William Seward, Ansel Adams, Theodore Roosevelt, and Henry David Thoreau were all notable conservationists, even if that title wasn't in their job descriptions. You may know some of these folks' names…and you may not.
It's a pretty strong guarantee that all of them did not do their good works in conservation in order to get into classroom study guides or even Wikipedia. Most conservationists do their good deeds for the public in a very private way.