Severe marine heatwaves, as well as hotter, more acidic waters are on the rise in the latest stocktake of New Zealand's marine environment.
Our Marine Environment 2022 is the third report by the Ministry for the Environment (MFE) and Stats NZ, and backs up growing research that sea levels are rising fast.
It brings together previous research, including that sea levels are rising twice as fast as previously thought, and new findings to paint a picture of the state of the environment.
The state of the sea
Latest data now shows ocean acidification is up 8.6 percent from data collected between 1998 and 2020.
Marine heatwaves are becoming more frequent and severe, and on average the sea-surface temperature increased by 0.1degC to 0.2degC per decade across the four oceanic regions.
Murky waters are becoming more common, with measurements for visual clarity across the country on the decline.
Coastal water quality is also degrading as it becomes increasingly polluted with faecal contamination and dissolved oxygen.
More sites did have an improvement in the rate of pollution for nutrients like nitrogen and phosphorus.
Between 2006 and 2020, 38 percent of water sites had worsening trends of Enterococci, an indicator of the suitability for recreation.
Plastic pollution is rising steadily, making up 70 percent of litter found along coastlines.
The report confirms previous research that sea levels are rising at fast rates, and in some areas it has doubled in the least 60 years.
Dunedin, Wellington and Lyttelton sea levels rose twice as much in the last 60 years compared with the previous six decades.
Stats NZ recently updated its coastal sea-level rise environmental indicator. It found that relative annual sea levels had risen faster over the last 60 years at four coastal monitoring sites.
Its environmental and agricultural statistics senior manager, Michele Lloyd, said last month that the rate had nearly doubled in the last 60 years compared with the first half of the century.
"Sea levels rose faster over the last 60 years, 1961 to 2020, compared with the previous 60 years, 1901 to 1960, at four main sites with records dating back to the 1890s and 1900s: Auckland, Wellington, Lyttelton and Dunedin.
"The rate of sea level rise has doubled in the last 60 years at three out of the four sites, Wellington, Lyttelton and Dunedin, compared with the mean rate from when records first began through to 1960."
Climate change was one of the main causes of sea-level rise, Stats NZ said. "As greenhouse gas emissions warm the Earth's atmosphere, heat is absorbed by the ocean. The expansion of sea water as it warms, combined with increased sea volume caused by the melting of glaciers and ice sheets, contribute to sea-level rise."
In the latest report, preliminary data suggests extreme wave events are increasing in the east and south of the country, but decreasing on the North Island's west coast and north of the Bay of Plenty.
Despite a decline in commercial trawl and dredge tows, accidental capture of marine species remains a "significant pressure" on some species.
Those in the firing line
MFE's deputy-secretary joint evidence, data and insights Natasha Lewis said when the marine environment was under stress it could affect things important to New Zealanders.
"For example, climate change is causing sea level rise, which impacts coastal communities, sites of cultural and ecological significance, and marine species. Sedimentation and pollution affect water quality, which can threaten biodiversity and public health," she said.
Coastal communities (more than 72,000 people) are currently at risk of coastal flooding, as are almost 50,000 buildings.
Thousands of kilometres of roads and water pipes and $26 billion worth of buildings are vulnerable to sea level rise of 0.6 metres.
Wāhi tapu and marae along the coastlines are also prone to risk.
Marine species and ecosystems are likely to be impacted by the increasingly hot, acidic and rising waters.
For example, in acidic waters shellfish struggle to grow and reproduce, and corals - which support a wide variety of sea life - can die.
Three-quarters of identified taonga species are threatened or close to being threatened by extinction, and most sea and shorebirds are threatened, the report showed.
There was new evidence that rising seas and storm surges were taking out nesting sites for shorebirds.
It comes after global research suggests a rare third year of La Niña conditions is likely. That would bring conditions for flooding in the north and drought in the south of Aotearoa this summer.
