Climate change: When the seas rise

On the up: Global sea level rise and its socio-economic impact on Aotearoa New Zealand

Professor Nicholas Golledge FRSNZ, Te Herenga Waka — Victoria University of Wellington

"In August 2021, the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) was released across the world. The report was described by United Nations Secretary General António Guterres as “code red for humanity”. Amongst the many hard-hitting headlines in the Summary for Policymakers was the statement that: “It is virtually certain that global mean sea level will continue to rise over the 21st century”.  Critically, however, the data showed that both the rate and magnitude of future sea level rise would be controlled to a large extent by our current and future greenhouse gas emissions. Far from being an inevitability, the future is still firmly in our hands.

Over the past seven years, we’ve been investigating what that means for New Zealand, through grants from the Ministry of Business, Innovation and Employment. Led jointly by Victoria University of Wellington and Earth Sciences New Zealand, our “NZ Searise” and “Our Changing Coast” programmes focus on the extent to which changes in the polar ice sheets influence global mean sea level, and  more specifically, how those global changes combine with vertical land movement around New Zealand to differentially affect our coastal communities.

This is a matter of both urgency and fiscal importance. The 2024 Ministry for the Environment “Coastal hazards and climate change guidance” report estimated building-related costs associated with a 1-in-100 year storm surge event, when combined with one metre of sea level rise, would be around NZ$38 billion. That’s a scenario entirely plausible by the end of the century. And it’s not just buildings. The risks to the necessary infrastructure that connects our societies are similarly substantial; nearly 3,000 km of road, almost 200 km of railways, as well as 14 airfields would all be vulnerable.

The disruption would be enormous. But what about the shorter term, the coming decades? A study in 2024 estimated that insurance companies will start to decrease their asset cover not just by the end of the century, but potentially within the next few years. By 2040, some parts of our major cities would be completely uninsurable, with concomitant social and economic ramifications. And as of August 2025, Tower Insurance, New Zealand’s oldest insurance company, is now including sea-level-related hazards in its risk assessments. This is a world first, but for the 5% of their customers at high risk of sea surge, the news of higher premiums will be most unwelcome.

One of the questions we’re trying to address in our research programmes is 'how we can accurately predict which communities will be most at risk?'. Our land goes up and down over time, even in between earthquakes. In areas such as the Bay of Plenty, or the southwest coast of the South Island, much of the coastline is rising by a few millimetres per year, effectively offsetting the 3 to 4 millimetres per year global sea level rise. But around much of the rest of the country the land is sinking. And this means that the relative rate of sea level rise is much higher than the global average, and the time we have to adapt to those changes is much less than it should be.

From the Far North to the Chatham Islands, we are bringing the physical science of projected ice sheet melt, local vertical land movement measurements, and coastal geological processes together with social science initiatives that directly engage with at-risk communities. Researchers from four New Zealand universities are working together with colleagues in the Public Research Organisations, as well as stakeholders and end users in diverse organisations across the motu, to tackle one of the biggest socio-economic problems that we currently face. But there is still a gap in New Zealand’s approach to adaptation, and in the future we hope that a national climate adaptation platform might be established to facilitate dialogue between policymakers, social and physical scientists, and indigenous and local communities.

With robust information and critical insight, we aim to provide our decision-makers with the information they need to achieve the first pillar of the Government’s 2024 Climate Change Strategy, in which “infrastructure is resilient and communities are well prepared”. Time is short, but with our multi-disciplinary and cross-sector research programmes, we are already well-placed to meet the challenges ahead."

Prof Golledge made the point that applied solutions to sea level rise are only possible because of fundamental research into the processes involved.

Pacific Climate Mobilities: population dynamics, community perspectives and youthful futures

Professor Yvonne Underhill-Sem MNZM (Cook Islands, Niue, Pākehā), Waipapa Taumata Rau | University of Auckland

"Pacific communities are aware of the impacts of climate change and are already discussing options for addressing these impacts. Based on community-based research in 17 communities in 7 countries in the Pacific, staying where they are is the overriding preference. The lands and waters of the Pacific are profoundly important to Pacific communities and, over deep and historical time, this has led to complex relationships between communities. These relationships become important as the pace of change impacting their lands and waters increases, from climate change but also other environmentally damaging activities. However, communities are pragmatic and strategic in considering their options, including engaging in various forms of mobility such as moving for work, education or marriage. Our research showed communities with decision-making processes, it highlighted clear perspectives from women and young people, and it showed that climate mobility was about more than the climate.

In terms of Pacific population dynamics, countries in the Western Pacific have the highest built-in population momentum and PNG alone is estimated to grow to about 15 million in 2050. Compare to Aotearoa (6.3 million) and the other 20 Pacific Island countries and territories (4.5 million) and it is clear that attention is needed to ensure equitable development across the region.

Please see more about this research.