Harper joined the Ecology Party's Scottish branch in 1985. At the time, the branch only had 35 members, and its AGM that year was held in his flat. He was elected unopposed as its convenor and secretary, and remained a leading figure as it became first the UK-wide Green Party, then the independent Scottish Green Party. He stood, unsuccessfully, as a Green candidate for Edinburgh Pentlands in the 1997 United Kingdom general election.
Scottish Parliament
Harper stood for election at the first ever Scottish Parliament election in 1999, and was elected as an additional member for the Lothians region, becoming the first ever elected Green Party parliamentarian in British political history. In an emotional speech, he promised to be a critical voice on the environment in the newly created devolved Parliament. He criticised the Scottish Executive's decision to split ministerial responsibility for the environment in 2001. He served as his party's sole representative in the first Parliament until the 2003 election, when the Scottish Green Party won another 6 seats in the regional lists. Harper was sworn in by giving the formal affirmation, also adding: "On behalf of the Scottish Green Party I wish to affirm that our priority will be to serve the people of Scotland who are sovereign in this land." He was the party's spokesman on education and young people. In 2004, he was a member of the Scottish Parliament team in the TV general knowledge show . He and fellow team members Richard Baker, Jamie Stone who was captain, and Stewart Stevenson beat a Welsh Assembly team by 110 points to 75. In January 2007, The Scotsman reported that Harper was being considered for the next Presiding Officer of the Scottish Parliament. Harper stated that he did not know of this story, but said "it would be an honour even to be considered". Following the 2007 elections to the Scottish Parliament, Harper was returned as a list MSP for the Lothians, this time one of only two Green Party members elected. After an agreement with the Scottish National Party, the party with the largest mandate from the election, the Green MSPs including Harper voted for Alex Salmond to become First Minister of Scotland but the Greens declined to enter a formal coalition with the Scottish National Party. As part of the deal, fellow Green MSP Patrick Harvie was nominated to head the Holyrood Transport, Infrastructure and Climate Change Committee. In 2009, Harper and Harvie voted to reject an SNP government budget. He did not seek re-election in 2011.
After Parliament
In 2011 his autobiography was published, written with journalist Fred Bridgland. In September 2014, Harper became chairman of the Scottish Wildlife Trust. He remained in that role for three years. At the beginning of December 2013, Harper announced that he would "absolutely vote no" in the 2014 referendum on Scottish independence, going on to say that he would be happy to help the Better Together campaign and that there was a "significant minority" of Greens who were opposed to independence.
