In 1901 he became president of the Vienna Zoological-Botanical Society (Zoologisch-Botanische Gesellschaft), and during the same year took part in a scientific expedition to Brazil. In 1919 he was appointed vice-president of the Vienna Academy of Sciences. During his later years (1929–30), he traveled with his son, Friedrich, to eastern and southern Africa.[4]
In 1913 Wettstein edited and distributed the last fascicles (specimens no. 3601-4000) of the famous exsiccata work Flora exsiccata Austro-Hungarica, a museo botanico universitatis vindobonensis edita.[7]