What is happening beneath the warming sea?
The sea shapes our identity as New Zealanders. It's warming. Rapidly.
My parents are SCUBA divers. Since I was born I’ve spent early mornings on boats with my dad or afternoons snorkelling while my mum and stepdad dived on Wellington’s south coast.
I’ve lived near water my entire life, including in the tropics where turtles, lionfish, and coral reefs thrive beneath the waves.
We have otherworldly beauty off the shores of New Zealand, too. In Whanganui, kahawai, snapper, eels and all sorts of crustaceans live where the river meets the sea.
Coastlines define us through connection to the moana in te ao Māori, the strong Pacific roots we share with other island nations, and the te ao Pākehā love of summers on the beach. Our oceans nourish us. They provide food and attract tourists from around the world. The sea shapes our identity as New Zealanders.
The coastlines that shape us are changing from all the pollution we are adding to the air. The sea level is rising, yes, but far more is happening under the rising tide. Pollution is causing havoc for the plants and animals that call our seas home.
For most of human history, the Whanganui coast has been mild. Over Christmas, my dad mentioned that it’s not that cold any more.
Dad’s been working off the coast of Whanganui for my entire life. When he started, winter waters hovered around 8°C. People dived in winter with drysuits to protect from the cold.
About 30 years later, winter water is “sub-tropical”. It can sometimes be five degrees warmer than it used to be. His divers don’t use drysuits in winter any more: they’re using their cooler wetsuits. “Otherwise, it's too hot”.
Our coastlines are full of plants and animals that have evolved to enjoy temperatures as they were. Penguins don’t feel freezing in Antarctica because they’ve evolved to feel comfortable at that temperature. It only feels freezing to us because that’s not our home. Imagine if penguins ruled the earth and chilled the average summer day to -10°C like Antarctic summers. It would be hell.
Human pollution is shifting temperatures in the other direction. The more our cars, gas stoves, cow burps, and coal plants pollute the air, the more heat the world absorbs from the sun.
The extra heat isn’t warming everything evenly. Underwater environments are getting hotter far faster than on land. The expert I spoke to confirmed that our oceans have absorbed 90% of the extra heat from climate change.
Our expert told me that our coasts are getting 0.3°C warmer on average every decade. In the context of earth’s entire history, that is scarily fast.
The rapid increase in heat means that sea animals would have to move five kilometres south every year to stay comfortable.
Some sea animals can migrate, but others can’t. Bull kelp forests, for example, are tethered to the sea floor. Our expert told me that when the water gets warm enough, the whole forest dies off and doesn’t grow back. It’s the underwater version of a forest fire.
Rising temperatures are distorting the natural balance of our coastlines. Fish depend on kelp as a home: when the kelp dies off, those fish are more likely to be eaten. New predators might move south to avoid sweltering waters. Algae that might not have thrived in cold coasts might now flourish. Ecosystems are a delicate balance. Heating the ocean with pollution is creating chaos.
My dad has seen the change first-hand. The marine growth has changed around the pipe he maintains off the coast. He’s seen “lots of differently coloured microbes, subtropical plants, and fish.” The blue maomao fish, which you’d normally find in Northland, is increasingly setting up shop on the southwest coast of Whanganui.
Dad has started preparing his crew with shark protection. “I had seen a thresher shark once in 23 years, and the next was this season, just hanging around the top.”
My dad’s experience is backed up by trends we’re seeing across Aotearoa.
Warming temperatures in the Marlborough Sounds have led to heatwaves which killed 40% of their farmed king salmon. Businesses like these that depend on stable temperatures will struggle to survive the future.
Pāua are increasingly under threat in our warming waters. Scientists have found that pāua struggle to grow above the minimum catch size when the water is above 21.5°C. That’s a risk to sea life and human livelihoods.
The worst part is that we have no idea what ecosystems below the waves will look like in warmer water. Our expert said that they couldn’t predict what will thrive off the coast of Wellington or Whanganui. We only know that ecosystems will change.
That uncertainty will bleed into our lives eventually. Will summer beach cricket be bookended by pāua fritters, or will they be too rare to eat? Will the marae be able to offer traditional kaimoana to manuhiri, or switch to new catch? Will visitors from across the globe be able to see Māui dolphins, or will the dolphins have fled south? Human history, traditions, and cultures will feel the chaos of a warming ocean sooner than you think.
When my dad chatted with me about what he’s seen in Whanganui, he said “it’s their home, not ours.” These plants and animals have zero choice in the matter of climate change, but they’re feeling the strongest effects.
New Zealand’s leaders are refusing to quickly build a cheaper, healthier, zero pollution society. The consequences of their inaction are already hitting our ocean neighbours.
We need to ask ourselves whether it’s worth sea creatures shouldering our burden so politicians can procrastinate. Will we wait for our leaders get their act together, or demand the better future our neighbours, above and below water, deserve?
