As much as $14 billion worth of council infrastructure is threatened by rising seas, prompting an urgent call for Government action.
A new Local Government New Zealand (LGNZ) report has mapped out various sea level rise scenarios, using LiDAR and other topographical data from 62 councils.
The report, developed with engineering consultancy Tonkin + Taylor, showed that $2.7 billion of roading, three waters, and building infrastructure is at risk from as little half a metre rise in sea level.
The value of at risk infrastructure ramped up sharply at each increment of sea level rise, with the data showing that $5.1b worth was at risk at 1 metre of sea level rise, with $7.1b at risk at 1.5m and $14.1b at risk at 3m.
LGNZ president Dave Cull said many councils were already experiencing the impact of sea level rise, most notably in the Bay of Plenty, the West Coast, South Dunedin and Hawke's Bay.
But, until now, there hadn't been an accurate, nationwide understanding of the community-owned infrastructure that was at risk.
"Using sea level rise scenarios that are based on the best local and international scientific advice, our research paints a really stark picture for local communities," he said.
"That's not even factoring in the total value of assets at risk from sea level rise, which skyrockets when you start factoring things that sit on top of this infrastructure, like highways, homes, businesses, office buildings, hospitals, factories and schools."
Cull said this showed the need to ramp adaptation efforts.
"As a small country our efforts in the mitigation space – while necessary – are not going to meaningfully move the dial on global carbon emissions," he said.
"But changes in the climate will definitely impact us, principally in the form of rising sea levels as two-third of all New Zealanders live within 5km of the sea."
The report recommended that central and local government jointly form a national adaptation fund to ensure that costs of adaptation were shared equally, lower socioeconomic households.
A new risk agency would also help councils understand and factor climate change risks into their planning, decision-making and procurement frameworks.
It further recommended a review of what local government services were being currently provided and what could be maintained over the short, medium and long term.
Its other major recommendation was teaming up with owners and users of exposed infrastructure to create a master plan setting out options and priorities for responding to sea level rise.
"Local councils have for many years led the policy debate around climate change adaptation in New Zealand," Cull said.
"We are literally on the front line, and have been engaging with residents, iwi, and businesses who are exposed to rising sea levels, but the threat is too big for us to fight alone."
Insurance Council of New Zealand chief executive Tim Grafton said the risks outlined in the report didn't tell half the story.
"This report should have everyone sitting up and listening," Grafton said.
"It has identified that over $5 billion of local government assets are at risk from a one metre sea-level rise, but we believe the full cost of exposure to central government and private sector property will be in the tens of billions of dollars.
"This is not just an issue for local government; central government has a key role to play too and ultimately carries the economic, social and political risk if adapting to sea-level rise is not well managed.
"Every dollar invested to reduce and adapt to risk now will save many more dollars in future post-disaster losses and help avoid social dislocation."
Climate Change Minister James Shaw said the Government was "acutely aware" of the impacts sea level rise could have on coastal communities.
"This report shows the sheer magnitude of devastation that could be caused by sea level rise. It would destroy critical infrastructure that allows our communities to function and thrive.
"The consequences of that are frightening. Evidence like that contained in LGNZ's report reinforces our resolve around the critical work we are doing to address climate change and limit sea level rise."
The Government intended to push ahead this year with work to establish a National Climate Change Risk Assessment system to help communities deal with the impacts of climate change, he said.
"That work will also incorporate consideration of the very difficult issue of how we spread the financial burden of climate change impacts."
Under present projections, the sea level around New Zealand is expected to rise between 30cm and 100cm this century.
Temperatures could also increase by several degrees by 2100.
Climate change would bring more floods; worsen freshwater problems and put more pressure on rivers and lakes; acidify our oceans; put even more species at risk and bring problems from the rest of the world.
Climate change was also expected to result in more large storms compounding the effects of sea-level rise.