He is a former co-chair of the party, having held the position from 2003 until standing down in April 2009.
In 2000, he moved to work at Queen's University Belfast.
Barry was Acting Director of the Institute of Governance, Public Policy and Social Research at Queen's University Belfast and is currently Reader in Politics in the School of Politics, International Studies and Philosophy and Assistant Director of the Institute for a Sustainable World.
He has written many books and academic articles on sustainable development, environmental policy and the economics of sustainability. He is co-editor of two academic journals, Environmental Politics and Ecopolitics Online.
By January 2003, he was elected as joint leader of the Green Party in Northern Ireland, alongside Kelly Andrews. He stood unsuccessfully in North Down at the 2003 Assembly election. He also stood in the Holywood ward for the local elections in 2005 and narrowly missed being elected by 60 votes.
He was a prime mover behind the creation of an all-island Green Party, officially launched in December 2006 in advance of the 2007 NI Assembly elections, which saw the Greens get their first Assembly seat in North Down with Brian Wilson.