Among its findings are that New Zealand’s oceans are warming faster than the global average, marine heatwaves are becoming more frequent and intense, the risk of invasive species and marine disease is increasing with climate change, and wetlands, dunes and native vegetation are being degraded.
Coastal homes and infrastructure at increasing risk of damage
The report found that in 2023, about 219,000 homes worth $180b were located in coastal inundation and inland flood zones.
An estimated 1300 homes – worth $900 million at current property prices – are set to experience greater than 20% damage in one or more extreme events between 2026 and 2060.
It gives the example of major erosion for Southland’s Bluecliff residents, where between 5 and 30m of erosion occurred along the shore of the Waiau River estuarine lagoon after a storm on September 21, 2023.
It points out that thousands of kilometres of roads, water pipes, and buildings worth a combined value of $26.18b were assessed in 2019 as being vulnerable if sea levels rise by 0.6m.
Under current climate conditions, about 288 landfills may be exposed to coastal flooding, and this increases to 379 with a sea-level rise of 0.4m, the report said.
Monitoring work of the seapods along the Tauranga harbour. Photo / Tauranga City Council
It found that over the next 20 years, New Zealanders are expected to build up to 76% more seawalls and similar coastal protection structures, in an effort to try to stop erosion and sea level rise.
“We can build some resilience for our coastal communities with seawalls, levees and other engineering options. But these options can have an environmental cost as coastal habitats and ecosystems are trapped between rising seas and built structures,” the report said.
Warming seas affecting industry
The report found that warming seas and ocean acidification are affecting the fisheries and aquaculture industries, which contribute $1.1b to GDP, and support more than 14,000 jobs.
New Zealand’s oceans are warming 34% faster than the global average warming rate, because of changes in atmospheric circulation and ocean currents.
Marine heatwaves, which the report finds will become more frequent, intense and long-lasting with climate change, have caused substantial decreases in fish catch and large losses in farmed salmon and mussels.
The report said warmer seas change the migration of fish populations and may reduce the growth rate of flat oysters and blue cod.
Warming seas and ocean acidification are affecting fisheries and aquaculture, impacting $1.1 billion GDP and 14,000 jobs. Photo / Getty Images
While warmer seas might increase certain types of fish – such as snapper and trevally – it is also likely to increase fish and shellfish diseases – such as “milky white flesh syndrome” in snapper.
Increasing sea-surface temperatures, and ocean acidification, are likely to increase toxic algal blooms, which accumulate in shellfish and fish and can also make people seriously ill.
Culturally important sites under threat
The report also outlined how significant cultural and archaeological sites are vulnerable to climate change, which could affect New Zealand’s cultural identity, connection to the environment and tourism industry.
It said marae and urupā (burial sites) were at risk of damage from extreme weather and that throughout the country, 191 marae are within 1km of the coast. That put cultural identity – through the passing on of knowledge and tikanga – at risk.
Nearly 2000 archaeological sites along the coastal zone are highly vulnerable to erosion from sea-level rise, and 1564 are at risk of flooding from the sea.
Over 120 public conservation sites and parts of 21 walking tracks are vulnerable to erosion, the report found. That includes four Great Walks – the Abel Tasman, Heaphy, Queen Charlotte and Rakiura tracks.
Some experiences for New Zealanders and international visitors could be lost altogether without action on climate change, the report said.
– RNZ