New Zealand's sea levels are rising, oceans are becoming more acidic, and marine heatwaves are becoming "more frequent and severe", a new report says.
The Ministry for the Environment and Stats NZ on Thursday released their Our Marine Environment 2022 report detailing the pressures on New Zealand's marine environment, its current state, and the impact that's having on the undersea ecosystem and coastal communities.
The report is published every three years and outlines key environmental indicators and the findings of peer-reviewed studies to paint a picture of our marine environment.
While the report makes the point that New Zealand has one of the largest exclusive economic zones in the world "with a diverse range of coastal and marine environments, habitats and species", these are "under pressure from climate change" and "degradation" from human activity.
"Efforts are being made to protect and restore New Zealand’s marine environment," it says. "However, Our Marine Environment 2022 shows us that whilst some aspects of the environment display improving trends, others continue to be at risk."
The increase in greenhouse gas emissions from human activities "continue to drive increased ocean acidification, sea-level rise and sea-surface temperatures", the report says, while commercial and recreational fishing, the introduction of non-indigenous species and coastal development are also having an impact.
Ocean acidity has increased 8.6 percent in the subantarctic surface water off the coast of Otago between 1998 and 2020, which the report says can have an impact on marine life.
"Ocean acidification may directly and indirectly affect a large number of marine mammals, as some species that have a narrow habitat tolerance struggle to adapt as they get nearer their biological limits.
"Increased acidity means shellfish may have to use more energy to grow their shells, which leaves less for tissue growth and reproduction… Many molluscs affected by ocean acidification are taonga species such as pāua and green-lipped mussels.
"Organisms such as deep-water corals form important biogenic habitats but are particularly susceptible to ocean acidification, which has negative impacts for the associated ecosystems."
The report notes the annual average coastal sea levels have risen at all six monitoring sites around New Zealand based on 2020 data.
"Sea levels are continuing to rise," the report says. "The annual mean coastal sea-level rise recorded between 1961 and 2020 was greater than between 1901 and 1960 at four long-term monitoring sites around Aotearoa."
The average sea-surface temperature has also risen by 0.1C to 0.2C per decade across New Zealand's four ocean regions between 1981 and 2018. The rise in coastal waters was an average of 0.2C per decade.
"Short-term and regional-scale variability in sea-surface temperature (or warming and cooling) has resulted in increasingly warmer summers and ongoing marine heatwaves, which are becoming more frequent and severe."
Ongoing sea-level rise and the potential for more frequent and intense extreme waves or storms "pose significant risks to the extent and health of coastal species and ecosystems, including the intertidal zone, estuaries, dunes, coastal lakes, and wetlands".
The report says sea level rise and storm surges have led to a loss of nesting sites for some shorebirds, while increased erosion and wave exposure "can impact seaweeds and animals".
"Increasing sea-surface temperatures can affect the growth and reproduction of some marine species, including plankton and snapper, which can affect the wider food web.
"Marine heatwaves can also disrupt species – for example, bull kelp suffered losses in Kaikōura and Lyttleton during the 2017/18 marine heatwave in Aotearoa."
Infrastructure on the coast is also at risk, the report says.
"Many communities are affected by climate change, with over 72,000 people and 49,700 buildings currently at risk from coastal flooding... Such events disrupt communities and damage buildings, which can impact the financial, physical, and mental health of individuals and communities."
Wāhi tapu and marae are also prone to erosion. The report says this will require "an adaption of tikanga practices and, in some cases, reburial or relocations".
"Many sites of importance for ecological, archaeological, and recreational purposes are in low-lying coastal areas at risk from coastal inundation with rising sea level, including 420 archaeological sites on Public Conservation Land."
Monitoring of coastal and estuarine water quality and sediment show "variable trends", with some improving. Marine habitats also continue to change, the report says, although high monitoring costs, particularly in remote and deep waters, mean officials have limited knowledge.
However, it's clear that "since human settlement, the condition of marine habitats has significantly declined, which in turn affects ecosystems and species".
"Many marine bird and identified taonga species are threatened with extinction or at risk of becoming threatened."
Professor Craig Steven from NIWA said the report "highlights some of the challenges coming from changing climate – things like marine heatwaves, acidifying oceans, sea level rise and damaging storms".
"These compound with more direct human impacts that come from plastics, fishing, and from our rivers. All of this affects the resilience of our biodiverse marine systems. Traditional knowledge practices, tikanga and kaimoana are central themes in the report, and they are being directly affected by these same pressures."
Environment Minister David Parker said the report painted a "sobering picture".
"Our Government is already taking action to address the range of pressures on the marine environment," he said.
"Water quality in coastal areas seems to be improving, with some areas showing reductions in the level of nutrients that can lead to harmful algal blooms.
"While improvements will take time, we expect these positive trends to continue as local councils implement the National Policy Statement on Freshwater Management, which we introduced in 2020."
He said the Government's Emissions Reduction Plan "is contributing to global efforts to limit temperature rise", while the National Adaptation Plan "sets out how Aotearoa New Zealand can adapt and build resilience to the impacts on our marine environment".
The Government's also banned single-use plastic bags and is phasing out other plastics, a common type of litter on beaches, he said.
Green Party spokesperson for oceans and fisheries Eugenie Sage said the Government should be doing more to protect our oceans.
"The report tells a decades-long story of government neglect when it comes to the health of our oceans," she said.
"Successive governments have allowed big industry to exploit our oceans for short-term economic gain. This has led to overfishing, trawling of the seafloor, excessive plastic pollution, and dirty fishing practices killing birds and other marine species.
"Worse still, the report’s over reliance on old data shows that government-after-government has known for decades the harm being done to our oceans. Had these warnings been heeded at any point in the last two decades, the health of our oceans would be very different. We'd be better off in numerous ways. But, as this report makes clear, that is not what has happened."
