On Sunset Beach in Port Waikato, two beachfront properties have been condemned after erosion of the sand dunes made them uninhabitable.

Cost to replace buildings affected by rising seas expected to exceed $19 billion

Replacing the buildings around New Zealand waiting to be lost to rising seas could exceed $19 billion, reports say.

Surf life saving clubs are already considering their options, but if the sea level rises by 1.5 metres, as expected by 2100, more than 6000 kilometres of drinking water, wastewater and stormwater pipes and 2000 kilometres of roads are also at risk, the recently released Our Marine Environment report says.

Climate change author Neville Peat, who published Invading Seas last year, said it was time to act.

"Councils need to be looking in more detail than what they have been up until now."

"The risks are pretty scary when you look at Napier, Christchurch and Dunedin, you can see some pretty scary numbers in terms of residences and treatment plants, substations at risk ... the numbers get up in to the thousands."

The expected increase in king tides would only increase that risk, he said.

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