environment

New report details threats to marine environment

The latest report from the Environmental Reporting Series looks at the threats facing marine life and habitats in New Zealand - and there are plenty of worrying signs with only a few causes for hope.

For the first time in three years, the Government has released a comprehensive report examining New Zealand's marine environment.

The report's conclusions are largely dire - species and habitats remain at risk and climate change and pollution are accelerating this process - but there are a handful of silver linings.

Alongside the report, the Ministry for the Environment (MfE) and Stats NZ have updated nine environmental indicators, compiling years of research to paint an up-to-date portrait of ocean life.

Outgoing Stats NZ chief executive Liz MacPherson said in a statement that "New Zealand has one of the largest Exclusive Economic Zones in the world, yet we know less about our coasts and oceans than any other environmental domain".

"It may be challenging, but it is absolutely critical that we continue to extend our knowledge and understanding of our precious marine ecosystems – our oceans, estuaries, coasts, and harbours, and the life within them."

Habitats and species threatened

The report identified four key issues facing New Zealand's marine environment. The first concluded that "our native marine species and habitats are under threat".

While seabirds, fish and marine invertebrates didn't receive an updated statistical investigation, marine mammals did for the first time in six years.

According to the 2019 data, 10 of New Zealand's 45 marine mammal species are threatened with or at risk of extinction. However, another 30 of those 45 are classified as "data deficient", meaning the Government is unable to determine whether they are at risk.

A chart from the new MfE report, showing the status of native marine species. Photo: Supplied.

Just five marine mammal species are considered "not threatened". Despite this gloomy outlook, the situation is improving for some species  - both the southern right whale and the New Zealand sea lion have become less threatened since 2013.

Invasive species a concern

Alongside the examination of native species, the report looked at the impact of non-native species in New Zealand waters. There are now 214 non-native marine species established in New Zealand - up three from MfE's last marine environment report in 2016, and up 21 over the last decade.

When it conducted its 2016 report, the ministry found it had little to no data on the status of biogenic habitats - those created by plants and animals. It commissioned a new study that is summarised in the 2019 report. 

Of the seven key habitats identified, four were thought to be shrinking, one was increasing and the remaining two were stable. However, predictions for the future were somewhat more positive - one was increasing, one was stable or increasing, one was stable, two were stable or decreasing, and the last two were decreasing.

Bryozoan thickets, which provide habitats for other animals and sequester carbon, and beds of large shellfish like mussels or oysters are the two habitats that are decreasing now and expected to continue doing so in the future.

New data on pollution the second issue

One of the most significant findings of the report came from so-called citizen science - data collated and provided by individuals not affiliated with the Government. This data concerned the quantity and type of beach litter.

People working with the Sustainable Coastlines Litter Intelligence programme conducted 44 surveys of beaches around the country in April. They found that plastic makes up three-fifths of all litter. Cigarettes, butts and filters play an outsized role in this figure, representing 11 percent of plastic items collected and 6 percent of all items overall.

Glass and ceramics made up another one-fifth of litter, followed by styrofoam at 6.2 percent, metal at 5.3 percent and wood at 2.1 percent.

This chart from the MFE report shows a breakdown of the types of litter found on New Zealand's beaches.

Alongside litter on beaches, the Government studied water quality. Sedimentation, or the accumulation of sediment, is a particular concern for the ministry, which found that annual rates of sedimentation are almost 200 times what they were for 10,000 years prior to the arrival of Europeans in New Zealand.

For nine out of twelve water quality variables - including phosphorus, turbidity and chlorophyll, more tested sites showed an improving trend than a worsening one. Only ammoniacal nitrogen, dissolved oxygen and total nitrogen were worsening in more places than they were improving.

Fishing also affecting environment

The ministry's third issue examined the ways in which activities at sea affected the marine environment. The new data it produced examined bycatch of protected species and found small trends indicating that the situation was improving. However, a ministry official cautioned that these trends were not necessarily statistically significant.

For seabirds, annual bycatch has almost halved in the 14 years between 2002 and 2016, dropping from 8192 estimated seabird deaths to 4186. However, this remains an issue for particularly vulnerable species like the toroa, or royal albatross, which are long-lived, slow to reproduce and more likely to be killed as bycatch than other seabirds.

In the 2016 fishing year, there were just three observed captures of sea lions, compared to 12 in the 2002 year. Fur seal captures dropped from 125 to 111 over the same period.

Over the decade between 2009 and 2018, one Māui and 29 Hector's dolphins were reported as entangled or potentially entangled, down from four and 60 respectively in the previous decade.

Seabed trawling can also irrevocably damage ecosystems and biogenic habitats, according to the ministry, but this practice has become less common. 

The elephant seal in the room

The report's fourth issue was climate change and its impact on the marine environment. New data on sea-level rise, coastal and ocean acidification, the population of phytoplankton and the frequency of extreme wave events was highlighted in the report.

New Zealand's oceans are warming at an alarming rate, according to the report. The last year that average coastal sea-surface temperatures fell below the long-term average was 2012. By 2100, sea-surface temperatures could have increased by as much as 2.5 degrees Celsius, the ministry said.

As the oceans warm, they lose their ability to absorb carbon dioxide. New Zealand's seas may take up more of the greenhouse gas than our forests, but that ability could decrease by between nine and 15 percent by 2100 due to temperature rise.

Since the ministry's last report on the marine environment in 2016, new data shows  "even faster rates of relative sea-level rise". Globally, mean sea levels have risen more than seven centimetres over the past quarter-century. By 2100, sea levels might have risen by a full metre.

As the seas warm and rise, extreme waves are becoming more common. An extreme wave event is defined as a 12-hour period where wave height equals or exceeds a given figure. In 2017 alone in New Zealand, there were 17 extreme wave events above the eight-metre mark in coastal regions and 16 in oceanic regions.

Extreme wave events are increasingly common according to this chart from MFE's report.

Subantarctic waters off the coast of Otago have seen a 7.1 percent increase in acidity over the past two decades. By 2100, waters around New Zealand could see a 100 percent increase in acidity, according to the Ministry.

As a slight silver lining, there was an increase in the amount of phytoplankton found on New Zealand's east coast and west of Fiordland. In Northland, the Coromandel and Bay of Plenty, phytoplankton populations decreased over the past 20 years.

Phytoplankton represent a broad measure of primary productivity, or the amount of energy created by living organisms. In general, the more phytoplankton in an area, the more and richer the marine life.

Issues combine

The report stresses that the four issues outlined above can't be taken in isolation. The bycatch data could represent a decrease in the amount of accidental birds and marine mammals taken - or it could show that the effects of climate change have decreased the populations of these animals.

As climate change alters habitats, invasive species may take root while native species struggle to adapt. On the other hand, as seas warm, phytoplankton may increase leading to more diverse marine life, at the same time as the ocean struggles to absorb carbon dioxide, accelerating climate change until seas become too warm.

It's difficult to find and analyse data on the cumulative effects of climate change, pollution, human activity at sea and invasive species, which makes it hard to understand the true scope of the issues facing New Zealand's marine environment.

Nonetheless, the report represents an attempt by the ministry to piece out some of what's going on, in order to inform future decisions on how to make a difference.

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