Helsinki, Paris, Stockholm, Chicago) and a visiting professorship at the University of Alberta in 1989 followed.
[5] He was honored in 1995 with the Richard Spruce Award by the International Association of Bryologists for excellence in bryology.
[6] Frahm conducted research on numerous topics of bryology and published more than 650 publications.
Frahm noted that the improved air quality in cities has led to an increased number of lichen species colonizing urban areas.
He also demonstrated that the release of ammonia by auto-catalysts causes nitrogen-loving lichens and mosses and nitrogen-emitting plants to settle along roads.