[3] He completed postgraduate study at Uppsala University in Sweden where he was awarded a PhD in 1985 for research on the botany of the Maytenus genus of plants in tropical Africa and Arabia.

[4] Demissew has participated in a number of successful collaborative research projects with universities in Europe and Africa including Oslo, Norway with Inger Nordal; Copenhagen, Denmark with Ib Friis; Marburg, Germany: the University of Leicester and Royal Botanic Gardens, Kew, UK; National Museums of Kenya, and South African National Botanical Institute in Cape Town & Pretoria, South Africa.

These projects have addressed floristics, biosystematics, vegetation, evolution in Afro alpine environments and under-utilized indigenous crops.

[8] Demissew has authored and co-authored books and articles in peer reviewed journals[5] on the vegetation and plants of Ethiopia and Africa.

[4] He served as Co-Chair of the Multidisciplinary Expert Panel for the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES).