[1] Kappen studied within the biological sciences at Freiburg and Göttingen, and was awarded a doctorate in 1963 for his work on the effects of environmental stress on ferns.
[2] Kappen's first academic post was at the Forest Botanical Institute of the University of Göttingen investigating cold tolerance in fir trees, grape vines, lichens and marine algae.
[1][2] His research involved studying the effects of abiotic stress, especially cold, heat, drought and light on plants.
His research took him to locations around the world including deserts, tropical rainforests and also seven expeditions to polar regions.
These include: In 1999 the Kappen Cliffs in the south edge of Kar Plateau on Scott Coast, Victoria Land, Antarctica were named after him by the New Zealand Geographic Board.