Johnston, known to his friends as Dave, was commemorated by both his fellow scientists and by the government. Known for his diligent and particular nature, he was called "an exemplary scientist" by a USGS dedication paper, which also described him as "unaffectedly genuine, with an infectious curiosity and enthusiasm". He was quick to "dissipate cynicism" and believed that "careful evaluation and interpretation" was the best approach to his work. An obituary notice for Johnston stated that at the time of his death he had been "among the leading young volcanologists in the world" and that his "enthusiasm and warmth" would be "missed at least as much as his scientific strength". Following the eruption, Harry Glicken and other geologists at the USGS dedicated their work to Johnston.