'Significant proportion' of New Zealanders under threat of sea level rise

Over 300,000 New Zealanders live below three metres of land elevation, putting them in danger from sea level rises.

As the threat continues to increase, a new paper explores how coastal communities can act now to protect themselves from sea level rising and erosion.

We're already seeing coastal erosion and occasional flooding during king tides and storms - and these are only going to get worse.

"They are happening more often, and we're seeing a shift over time to coastal flooding becoming the dominant coastal risk over erosion due to rising sea levels," says Dr Rob Bell from NIWA.

Hawke's Bay residents have worked with council and iwi to create a strategy extending more than a century.

Using new planning tools, communities are able to take a longer term view and look at how to transition to rising sea levels.

"We must start making transitional changes to transform our coastal communities as seas rise and coastal flooding becomes an unavoidable reality," says Dr Judy Lawrence, one of the researchers involved in the study.

"Moving away from thinking we can continue to stop the sea by using hard structures is a first step. Holding the shoreline has limits, not least being affordability.

"There are adaptation choices, but they will require lead-time to implement."

Dr Bell warns short-term solutions won't help deal with a long-term problem.

"You can elevate houses, you can build seawalls... but all have a limited life-span in terms of their effectiveness," he told Newshub.

"A lot of our exposure is in the first one-metre of sea-level rise. And so a number of our communities are already seeing increasing coastal flooding, increasing coastal erosions."

And while scientists know climate change is affecting sea levels, some of the effects can take decades to manifest, making modelling difficult.

"We know that the sea is rising, and have a good estimate on the range of sea level rise up to about 2050. After that, we are much less certain as we don't know the exact timing of change - including polar ice sheet responses - nor how fast the world will reduce its carbon emissions," Dr Lawrence says.

"So decisions about settlements beside the sea need to be made with precaution and the flexibility to shift pathways."