Scots voters look certain to be asked to return another six MEPs as the likely extension to Brexit means the UK will have to take part in the European elections at the end of May.
The Greens are staging their spring conference in Edinburgh over the next two days and will stage a hustings tomorrow as part of its candidate selection. Mr Harvie is to address delegates this morning.
He will say: “A myth has been allowed to develop that only the far right populists are gaining ground in Europe.
“But while they do pose a serious threat, the truth is that in many European countries it’s the Greens people are turning to for a positive vision of the future.”
Mr Harvie will also tell supporters the party must broaden its appeal as it looks to make gains across Scotland.
“We need to be ready to win more Holyrood seats, building on the gains we made in 2016 and filling in those gaps on the map where three regions of Scotland don’t yet have a Green MSP,” Mr Harvie is expected to say.
“We need to broaden the appeal of Green ideas to every part of our country, because every single one of us is involved in the greatest challenges of our age, and every single one of us is being failed by middle ground politics - or worse, by the idea that something moderate is the only alternative to something toxic.”
The party’s co-convener, Maggie Chapman, is expected to praise the campaigning efforts of young people who walked out of school to demand action on climate change as she addresses delegates this morning.
“We have a huge opportunity to support the school strikes as a social movement,” Ms Chapman will say.
“Our young people are leading the way in challenging the systems and structures of our politics and our economy.
“We must listen to them. The age of individual action is dead. Now is the time for social movements to seize power.”
She will add: “Other parties think that change happens only by winning power and then imposing change on the people.
“But Greens know, because of our roots in participatory democracy and our experiences in communities, that real change is different.
“It is about supporting and being a part of building wider social movements, bringing people in, and working constructively to create change.”