He stressed that global temperature variations were the primary cause of profound environmental changes, and that a study of fossil pollen would produce a wealth of information about palaeoenvironments.[2] In this regard he worked at several sites in southern and eastern Africa with J. Desmond Clark, extending the scope of his research to include the Sahara and Namib deserts and the sub-Antarctic islands of Prince Edward and Marion. In 1965 he arranged the first major research expedition to these islands made up of an international team of 35 specialists who studied palynology, glacial geology, vulcanology, limnology, mineral cycling and bio-energetics. The results were published in a 1971 monograph.