After graduating with his BA in 1952 from Clark University, Ahmadjian served for two years in the United States Army in the Combat Medical Corps during the Korean War.
Upon his return to civilian life, Ahmadjian continued his studies at Clark, receiving his MA in 1956, and then went on to achieve his PhD from Harvard University in 1960.
In 1995, he published an invited letter in BioScience stating that lichens were the dominant organism in 8% of terrestrial habitats on Earth, attributing this statistic to Douglas W. Larson.
A 2024 study by Drotos et al. traced the origins of this statistic, revealing it to be an unevidenced estimate that proliferated through scientific literature without critical evaluation.
The study found 76 academic articles and 37 popular media items repeating variations of this claim, highlighting the importance of rigorous citation practices in scientific communication.