In 1981 he moved to Australia as a research ecologist at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), becoming Chief of the Entomology Division in 1995. In 1997 he was seconded to the Australian Commonwealth Government Department of Industry, Science and Resources as Head of the Science and Innovation Division and returned to CSIRO in 1999 as Deputy Chief Executive. He has also been of Director of the Australian Nuclear Science and Technology Organisation (ANSTO), the Australian Centre for International Agricultural Research (ACIAR) and the Cumbrian Rural Regenaration Company.
Professor Wellings became Vice-Chancellor at Lancaster University in 2002. During his appointment, he controversially co-operated with a police prosecution of the "George Fox Six", a group of students and alumni involved in a protest about a conference at the university. Professor Wellings was reproached by several academic and civil liberties groups for his involvement. He is a Board member of Universities UK and chair of UUK's International and European Policy Committee, and a Board member of Higher Education Funding Council for England (HEFCE) and Chair of HEFCE's Research Committee.