Climate change is a bigger problem than the Brexit deadlock, and governments need to prepare for it, said Clare Bailey of the Green Party of NI.
The South Belfast MLA spoke at its first conference as party leader.
She replaced Steven Agnew in November.
Ms. Bailey said the borders are "of little importance in the face of climate collapse," and she called for the restoration of Stormont to put into effect a policy.
Northern Ireland has not had a functioning decentralized government since January 2017 when institutions collapsed following a scandal for renewable energy.
Ms. Bailey said Brexit had resumed the debate on an Irish border survey, but she focused on questioning another topic altogether.
"Many say they want a so-called new Ireland, while others want to entertain the UK at any cost," said Ms. Bailey.
"For all of us is threatening a new reality – it's called climate collapse.
"Do you want to see changes?"
"A border along the Irish Sea or over the island of Ireland is of little importance given the collapse of the climate.
"We have not returned 12 years to any point unless we radically change our way of life.
"The climate chaos is real and that comes, regardless of constitutional changes."
The Green party in Northern Ireland has two MLAs and a number of councilors.
Ms. Bailey said her focus is on increasing the electoral success of the party in the May general election.
She said the party wanted to reach out to young voters and target those who would have traditionally elected unionists or nationalists but were frustrated with Stormont's storm.
"I do not take for granted that they are coming to the Greens, but we want to see changes," she said.
"We can not always stick to the same thing and expect different results."