[3] He began his career as a scientist working on renewable energy at the University of Aberdeen and then as a Projects Officer with Central Scotland Countryside Trust.

Author of a number of reports on these topics, he also served as a Specialist Adviser to the UK Parliament's Scottish Affairs Committee Inquiry on land reform 2014–2015.

The campaign has the stated aim of supporting local residents through seeking to democratise companies that are run by a handful of people who are not living on the land involved.

[12] Wightman was one of a group of Scottish politicians (two MSPs, an MP and three MEPs) who instituted proceedings against HM Government to clarify, through a judgment of the European Court of Justice, whether the Article 50 notice that formally started the Brexit process could be revoked unilaterally by the United Kingdom.

[15][16] On 18 December 2020, Wightman announced his resignation from the Scottish Greens following a vote on an amendment to the Forensic Medical Services (Victims of Sexual Offences) (Scotland) Bill,[17] alleging that the party was intolerant to discussion of potential clashes between transgender and women's rights.

He stated in his resignation letter that voting for the amendment (and against the party whip) would have resulted in "complaints and disciplinary action leading to possible suspension, deselection or expulsion".