Prof Ayensu obtained his M.Sc. in 1963 from George Washington University and a PhD in 1966 from the University of London. He then became Scientist-in-charge of the Smithsonian biological survey at Smithsonian Institution (US).
His research interests focus on tropical biology and ecology, economic botany, comparative anatomy and phylogeny of flowering plants, behaviour of fruit-eating bats, biomedical research of medicinal plants, development of low carbon growth plants and development of biomass plantations for bio energy.
He has investigated major World Bank Development Projects such as the Chad-Cameroon Oil Pipeline, Petroleum Sector Management Capacity Building, China Western Poverty Reduction and Brazil Land Reform Poverty Alleviation. He has served as Director and Senior Scientist at the Smithsonian Institution and Senior Advisor to the President on Strategic Planning and Policy Development at the African Development Bank.
He served as Chairman of Africa Practice, the Council for Scientific and Industrial Research (CSIR) in Ghana, etc. He was a member of the Board of Trustees of (1) the UN University for Peace, (2) the management of intellectual property rights in health research and development (MIHR, UK), and of the Energy Commission at the World Bank for the development of the West African gas pipeline. He is a founding Fellow of The African Academy of Sciences, and a member of TWAS.