Coastal floods will become increasingly commonplace in New Zealand over the next 80 years, new global research suggests, brought on by climate change and extreme sea level rises.
The Melbourne University research paper, published recently in Nature's Scientific Reports journal, shows coastal flooding around the world has the potential to threaten hundreds of millions of people and take a colossal toll on the global economy.
Major risk areas have been noted in every continent, with northwest Europe the most exposed region in the world - although existing flood defences already provide protection there.
However, there are also "hotspots in Australia, New Zealand, China, India, South-East Asia, southeastern Africa, and North America," according to report co-author Professor Ian Young.
Our west coast is the portion of New Zealand's shoreline most threatened by coastal flooding, a map shows.
"The increase of extreme sea levels around New Zealand will rise from 1.5 to 2.5 metres to 2.5 to 5 metres," lead author Ebru Kirezci told Newshub.
"Particularly on the western coast - these parts are going to see some increases in extreme seas. The increase in extreme sea [levels] may pose a potential for coastal flooding."
The study shows the years between now and 2100 will see an increased flood risk for 48 percent of the world's land area, with 225 million people likely to be threatened by extreme sea level rise.
The economic risk posed by coastal floods totals a barely conceivable US$14.2 trillion (NZ$21.43 trillion) - one-fifth of the world's gross domestic product (GDP) - based on a climate scenario where global carbon dioxide emissions continue to rise at the same rate.
"A warming climate is driving sea-level rise because water expands as it warms, and glaciers are melting. Climate change is also increasing the frequency of extreme seas, which will further increase the risk of flooding," Kirezci said.
"What the data and our model is saying is that compared with now, what we see as a one-in-100-year extreme flood event will be 10 times more frequent because of climate change.”
'It's a wake-up call': How the world and NZ should react
When asked about the specific threat to New Zealand, Kirezci said it required further investigation - but Prof Young said the research acts as a "wake-up call" for governments across the globe.
"This is critical research from a policy point of view because it provides politicians with a credible estimate of the risks and costs we are facing, and a basis for taking action," he said.
Prof Young believes the study's results should "inform policy at a global and local government-level", enabling more flood defences to be built to safeguard coastal life and infrastructure.
"Our research shows that large parts of communities residing in low-lying coastal areas are at risk of being devastated so we need urgent action," Kirezci added.
"Vulnerable areas need to start building coastal defences, we need to increase our preparedness, and we need to be following strategies to mitigate climate change."
However, Kirezci admits any positive climate action is likely to be too little, too late.
"There's more research required," she told Newshub.
"But still, sea level rises are already happening and will continue to happen no matter what we do."