New Zealand's buildings, water supplies and population in general have been deemed at "extreme risk" of climate change impacts this century, which could come with 3C of temperature rise and seas nearly 70cm higher.
The Government today released a sweeping national risk assessment, rating for the first time which of 43 areas, across five domains, should be priorities in preparing the country for a warmer and wilder future.
Among 10 urgent areas, the assessment – based on emissions rising at the current rate and resulting in a projected 67cm of sea level rise and 3C of temperature increase by 2090 – found we ourselves to be at "extreme" risk, with threats of people and communities being displaced, and inequities widening.
About 675,500 Kiwis lived in areas already prone to flooding, with a further 72,065 living in the firing line of where some of the most dramatic effects of sea level rise could hit.
People being forced to shift came with more pressure on social services, labour and housing markets, along with broken social bonds and shrunken communities losing essential services.
Buildings, too, were at extreme risk – nearly 50,000 of them were currently exposed to coastal flooding, and at the highest range of warming scenarios, that could rise to nearly 120,000 this century.
The assessment pointed out how the flooding of 800 homes in South Dunedin in 2015 resulted in more than $28 million in insurance claims.
There was similarly extreme risk to water supplies, with droughts like this summer's big dry projected to increase in most regions, and population growth ramping up in many already exposed places: notably Auckland, Bay of Plenty, Northland, Waikato, Greater Wellington, Hawke's Bay and Otago.
The assessment further assigned an extreme risk around governance - council plans, legislation and funding mechanisms weren't fit for adaptation – and to the economic impact on government, directly from lost productivity and covering disaster relief bills.
A rating of "major risk" was assigned to the financial system, from instability caused by extreme weather events, and also to New Zealand's already under-pressure natural environment.
Victoria University climate scientist Professor James Renwick said the report made for "sobering reading".
"Climate change affects everything we depend on, everything we eat and drink, as well as our way of life and livelihoods," he said.
"Rising temperatures, changing rainfall patterns, sea-level rise and increasing extreme events are already affecting Aotearoa New Zealand and will have increasingly damaging effects in future.
"This report takes an appropriately broad view, but recognises there are some fairly fundamental things we just don't know."
For instance, we still had limited knowledge of the effects on natural ecosystems, effects on cultural heritage and spiritual wellbeing for Māori.
"We do not even have consistent national information on the exposure of the built environment to climate hazards, so there is clearly work to do."
In response to the risk assessment, the Government now had two years to come up with a national adaptation plan.
"There is clearly an urgent need for such a plan, but even so, it must be designed carefully."
Renwick noted the report pointed how current governance systems could even end up making the situation worse through "maladaptation".
"We do not want to paint ourselves into any corners by locking in further high-carbon infrastructure or by making ourselves more vulnerable to climate change hazards."
Niwa coastal scientist Dr Rob Bell said New Zealand likely only had a few decades to get proper plans in place to prepare for rising seas.
Bell said scientists were quickly trying to build a clearer picture around several key areas of uncertainty.
They included much sea-level rise would come from melting polar ice sheets, how badly communities could be hit by "flood sandwiches" of higher rainfalls and tides, swollen rivers and storm surges, and how estuaries, lowland rivers and groundwater systems would cope with more saltwater.
Another prominent expert, climate scientist Professor Jim Salinger, said the report was timely in that it demonstrated the need for urgent action now.
"Overall, in my view, it is a wide-ranging and comprehensive assessment of climate change risks over many sectors," Salinger said.
"Essentially the largest risks come from storm surges with sea-level rise, increases in high-intensity rainfall affecting erosion, flooding, property and infrastructure," he said.
"Increases in temperature increase the risk of heatwaves which produce all sorts of impacts on the natural environments and ecology - as instanced by the back-to-back heatwaves of 2017/18 and 2018/19, which destroyed some coastal marine ecosystems, and produced dramatic melting of Southern Alps glaciers."
But Salinger felt there wasn't enough information in the assessment about the knock-on impacts from a melting alpine environment, or from a changing ocean altering marine ecosystems.
"The report also notes that pine forests will grow faster as an advantage: unfortunately in many areas of the South Island wilding pines are regarded as a major pest species invading and destroying sub-alpine ecosystems."
Climate Sigma managing director Belinda Storey said that, up until now, New Zealand had lagged behind other countries for nearly a decade in not having a national risk assessment.
"While the report looks at climate out to 2100, by applying an engineering lens, the assessment could bias the national adaptation plan to solutions that reduce short-term risk only," said Storey, who also oversees Whakahura: Extreme Events and the Emergence of Climate Change Programme.
"The hope is the next iteration of this assessment can shift our focus more to reducing long-term residual risk."
Storey saw the document as key in deciding the path of New Zealand's future, and it was vital that it didn't constrain future assessments.
"By necessity, due to the short timeframe of this assessment, it is only a high-level review of a very complicated issue," she said.
"In particular by naming a 'top ten' of risks it narrows the focus dangerously away from other issues that may not have been fully identified by the authors."
A deeper dig was now needed into long-term implications and into wider social and economic issues.
"In my first read of the assessment it strikes me as light on finance. Finance can be a key lever in adaptation to climate change," she said.
"For example a bank's decision to require higher initial deposits and shorter mortgage periods for flood-prone houses may have more impact than local government's attempt to constrain development in hazardous locations by recording the extent of sea-level rise in district plans."
Climate Change Minister James Shaw many communities were now experiencing life under a changing climate.
"However, that does not mean our goal of preserving a safe climate for the future is not within reach," he said.
"Because it is."
Shaw said the Government had already acted by passing zero carbon legislation, reforming the Emissions Trading Scheme and supporting public institutions to switch to clean energy.
"Cutting our emissions is obviously a huge part of what we need to do to create clean, safe and healthy communities for ourselves, our loved ones and future generations.
"However, the climate is already changing and there will be some effects that we cannot avoid.
"So, in addition to driving the transition to a zero carbon New Zealand, this Government is also working to ensure our communities are made much more resilient to the unavoidable effects of global climate change."
The assessment comes days after a high-level panel recommended the Government introduce an entirely new piece of legislation focused on dealing with climate-driven impacts.
Another new poll, released by insurer IAG, indicated nearly half of Kiwis thought government actions were now good – up from just a third in 2018 – and nearly four in 10 felt New Zealand would be able to hit its emissions reduction targets, despite analyses showing the country is so far falling short.
The majority of respondents also thought they would be personally affected by it – for instance, more than 80 per cent believed the world would see more extreme droughts, floods, storms and water shortages – and nearly two thirds were already taking steps to minimise its impact on them.
But nearly a third were more worried about how climate change would impact them, rather than about their impact on climate change.
Under the Paris accord, New Zealand has pledged to slash emissions by 30 per cent below 2005 levels, and 11 per cent below 1990 levels, by 2030.
Shaw has tasked the recently formed Climate Change Commission to investigate whether those targets – which sit alongside the Government's zero-carbon 2050 goal – are ambitious enough to meet the UN's aspirational target of limiting warming to 1.5C above pre-industrial levels.
Climate change and NZ: Six big trends
• In the last 100 years, our climate has warmed by 1C. If global emissions remain high, temperatures will increase by a further 1C by 2040 and 3C by 2090, with the greatest warming likely to be in the northeast.
• In the last 60 years, sea levels have risen by 2.44mm per year. If global emissions remain high, sea levels will increase by a further 21cm by 2040 and 67cm by 2090.
• Extreme weather events such as storms, heatwaves and heavy rainfall are likely to be more frequent and intense. Large increases in extreme rainfall are expected everywhere in the country.
• The number of frost and snow days are projected to decrease.
• Drought is predicted to increase in frequency and severity, particularly along the eastern side of the Southern Alps.
• Wildfire risk is predicted to increase.