Ocean & Biodiversity
Our ocean is warming, rising, and becoming more acidic with climate change.
As an island nation, Aotearoa New Zealand's ocean is 15 times larger than our land. Many of us connect with the ocean in our daily lives - at the beach, swimming, and gathering kai moana (seafood).
But climate change is affecting our ocean, causing acidification, warming and sea-level rise. These changes threaten the plants and animals that live in our ocean, as well as the people and communities who live near it.
The plants and animals in the ocean all depend on each other for food and these connections form what we call a 'food web'.
Energy at the base of food webs comes from the sun. This energy is absorbed by ocean plants and moves up through the food web.
In te ao Māori (Māori worldview), physical and spiritual energies such as mauri, hau, tapu, wairua and hihiri give life to humans as well as te taiao (the environment). This connection between all things means that changes in energy balance in part of a food web will flow through the whole food web, including to humans.
To understand what's going on, let's take a look at how climate change is impacting our ocean - with examples from the base of our food web to the top.
How is climate change affecting our ocean food webs?
Base of the food web
At the base of our ocean food webs are phytoplankton. Phyto means plant, plankton means to drift - so phytoplankton are microscopic drifting plants in our ocean.
Climate change is affecting phytoplankton, with decreases in some regions (shown in lighter green) and increases in others (shown in darker green).
These changes impact how much energy is available for other species, including important kai moana species. If food is not available in the right place or right time for fish, shellfish and other species, their populations will decline.
This shows how climate change is altering the whole ocean food web.
- Explore this map to see how phytoplankton has been changing in our ocean (1997 - 2018).
- For more information see the link below.
Ocean acidification
As we move up the food web, animals that eat phytoplankton are affected by climate change in different ways.
Global oceans have absorbed approximately 25 percent of total human carbon emissions since the start of the industrial revolution.
Our oceans are becoming more acidic as they absorb carbon dioxide from the atmosphere.
Increased acidity means it will be more difficult for shellfish to build their shells. This means they can be more easily damaged and leaves less energy for other things such as reproduction.
This will particularly affect young taonga (treasured) species such as pāua and kuku (green-lipped mussels) that are important for kai moana, as well as for fisheries and aquaculture.
- For more information see the link below.
Ocean warming
The surface of our ocean is warming with climate change.
Plants and animals that find it difficult to move to a new habitat, such as kuku and rimupara (bull kelp), can struggle to survive in changing temperatures.
Animals higher up in the food web that feed on kuku, such as snapper, might have to move to find new habitats with temperatures they need to survive. Whole ecosystems may change as the ocean warms.
Ocean warming also contributes to sea level rise, as warm water expands and takes up more volume. This adds to sea-level rise caused by melting ice sheet and glaciers. As an island nation, Aotearoa is particularly vulnerable to coastal flooding...
- Explore this map and chart to see coastal sea-surface temperature in your local area (2002 - 2018). On the map, red shows stronger warming of up to 0.7 degrees Celsius.
- For more information see the link below.
New Zealand coastal sea surface temperature 1953-2014
Sea-level rise
Annual mean coastal sea-level rise
Climate change is causing our sea-levels to rise and is already leading to more frequent flooding along our coasts.
This is particularly important for native animals higher up the food web, that rely on estuaries, dunes, coastal lakes, and wetlands for their food sources.
Native animals that live and nest in these places will be restricted by the rising sea-level at one side, and the way humans are using land on the other. So as sea-levels rise, their habitats will be 'squeezed'.
This coastal squeeze will particularly affect our shorebirds that make their nests in these areas.
As sea levels continue to rise the flooding will get worse...
Coastal flooding with 10 cm of sea-level rise
With every bit of sea-level rise, we will see changes in the risk of flooding.
Native bird nesting and feeding grounds, such as around Farewell Spit, are at risk.
Farewell Spit is an important habitat for many native shorebirds, including gannets that nest near the sea.
With 10 cm of sea-level rise, a coastal flood predicted to happen '1 in 100 years' could cover the yellow area of the map.
- Explore this map to see what this could look like in your local area.
Coastal flooding with 1 metre of sea-level rise
With 1 metre of sea-level rise, a coastal flood predicted to happen '1 in 100 years' could cover the orange area of the map.
- Explore this map to see what this could look like in your local area
Coastal flooding with 2 metres of sea-level rise
With 2 metres of sea-level rise, a coastal flood predicted to happen '1 in 100 years' could cover the red area of the map.
- Explore this map to see what this could look like in your local area.
- For more information see the link below.
Ocean species are at risk
Here we have highlighted just a few of our many ocean species that are affected by climate change. Many of our ocean species are under threat from fishing and pollution. But climate change is impacting our ocean food web as a whole, which is adding stress to already threatened species. For more information about the challenges facing our ocean species see the link below.
Many of our ocean species at risk are taonga species. In te ao Maori, if the mauri of the ocean is degraded, then the mauri of taonga species and communities that engage with the ocean are also affected.
- Explore the population trend and extinction threat status of our different ocean species by clicking on a species name.
- If you're viewing this page on mobile, click any bubbles to enlarge the graphic.
What's being done to help?
Kuku restoration
We have explored how climate change impacts such as ocean acidification, warming oceans, and sea-level rise are adding stress to our ocean food web.
This is a particular challenge for kuku beds which had already been degraded by enhanced water nutrients and sediment, trawling, dredging, and harvesting.
Now let's hear about how Mātauranga Māori (Māori knowledge) and western science are being combined to restore kuku in Ōhiwa Harbour...
The kuku population at Ōhiwa Harbour fell from 112 million to just 80,000 between 2007 and 2019, according to Professor Kura Paul-Burke.
Local communities and researchers have been taking action to restore these taonga and protect them from the challenges they face.
By 2021 the kuku population had increased to 800,000. Ngāti Awa kaumātua identified areas appropriate for mussel restoration, and by July 2023 mussel beds in these locations were confirmed to have strong kuku populations of 16 million.
Hear Kura Paul-Burke talk with RNZ about kuku restoration:
- For more information see the link below.
Now let's see what else is happening across te taiao with climate change...
