Speaking at Dynamic Earth in Edinburgh, Mr Harvie said his party’s past frustrations at a lack of progress over climate change, the economy and a “failed social fabric” could be turned into action as a result of the co-operation agreement with the SNP.
Mr Harvie and fellow co-leader Lorna Slater were given ministerial office as part of the power-sharing agreement signed in August.
“On the streets and the doorsteps, our work creates an urgent call for change, just as we’ve always done for nearly 50 years of our movement’s history, 30 for our own party’s history,” he said.
“In Parliament, we’re bringing constructive challenge into politics and bringing a voice to the communities we represent, just as we’ve done since 1999.
“And now, in Government, we’re turning rhetoric into action.
“Now, more than ever, thanks to the hard work of our members and campaigners, the Scottish Greens are working for Scotland.
“And now, more than ever, Scotland needs us.”
Mr Harvie said Green MSPs are putting inequality “at the heart of the recovery strategy”.
Ms Slater stressed the importance of the party’s policy decisions, saying: “As we meet this weekend we can do so with more than just hope – we can do it with the knowledge that the policies we discuss can change the lives of people across our country.
“The agreement that we negotiated will deliver real and positive change for our climate and our communities.”
Ms Slater also attacked the UK Government and Prime Minister in her speech, claiming their actions are pushing people towards supporting Scottish independence.
She said: “Very soon, the eyes of the world will be on Scotland for Cop26.
“What will they see? The Prime Minister has said he does not want the Scottish Government to be involved in case they see it as an advert for independence.
“Every day that Boris Johnson and his colleagues stand in Downing Street is an advert for Scottish independence.”
Scotland “can do so much better than this”, Ms Slater continued.
“With the full powers of independence, we can take a different path, we can build a better society.
“We can build our circular economy and invest in people, we can be a European leader in renewable energy.
“We can build a Scotland that works with our friends and neighbours, a Scotland that stands in solidarity with people living under oppression, and a Scotland that welcomes refugees and extends the hand of friendship around the world.
“It won’t always be easy, there will be difficult moments, but there always is when history is being made.”
Mr Harvie took his own swipe at the UK Government, branding them “extremists”.
He said the UK Government is “desperate to look inwards, savagely cutting international development funding, ignoring climate science and undermining Scotland’s Parliament”.
“Conference, we look at these horrors and we know we must defend our homes from these extremists,” he said.
“That’s true whether our home means our planet, our country or the roof over our heads.”