Key points
- The ocean provides NSW with environmental, social, cultural and economic benefits. These benefits rely on water quality and biodiversity in the ocean.
- Climate change is changing ocean currents and increasing the average sea surface temperature around Australia, which is leading to marine heatwaves and impacts on marine biodiversity. These impacts are expected to intensify.
- The best way to reduce the impacts of climate change on our oceans is to reduce greenhouse gas emissions.
The importance of the ocean in NSW
The NSW coast lies on the western edge of the Pacific Ocean, where the Coral Sea (off the north coast) meets the Tasman Sea (off the south and central coast). This meeting point creates both a coastal biodiversity hotspot and a site of heightened vulnerability to climate change. The ocean provides important environmental, social, cultural and economic benefits to NSW.
Some ocean benefits are tangible and their value can be measured, such as commercial fisheries and marine tourism. Others are intangible, such as the benefits to human health and wellbeing when people experience nature.
The ocean provides many different economic values. Australia conducts 99% of its trade through ports. Ports in Newcastle, Port Kembla and Sydney are a central part of NSW's and Australia's supply chain. Other economic services include seafood from our commercial fishery, aquaculture and marine, as well as cruise ship tourism.
Recreational activities can also provide economic benefits. Such activities include:
- whale watching
- recreational and cultural fishing
- kayaking
- sailing
- scuba diving
- surfing
- relaxing on the beach.
For many people who live in NSW, the ocean provides social and cultural benefits and supports their emotional wellbeing. Our oceans make up part of the cultural fabric of NSW.
The ocean also influences the NSW climate system.
How the ocean is affected by climate change in NSW
Oceans cover more than two-thirds of the Earth’s surface and hold about 96.5% of all water. The Earth’s oceans:
- produce around 50% of the world's oxygen
- absorb around 30% of carbon dioxide emissions
- absorb 93% of the extra heat that comes from greenhouse gas emissions.
The ability of the oceans to absorb extra carbon dioxide and heat is not endless. The heat and carbon dioxide already absorbed are having major effects on ocean temperatures, ocean acidification and sea level rise. These are affecting biodiversity and marine ecosystems, and threatening the ecosystem values and services that the ocean provides. These impacts are projected to intensify as our climate continues to change.
The clearest impact of climate change is the warming of our oceans, particularly of surface layers that are in closest contact with the atmosphere.
Long-term sea surface temperature data show a strong warming trend off south-east Australia over the past 100 years. This is affecting the physical, chemical and biological characteristics of Australia’s marine environment, with impacts including changed marine species distribution along the coast of NSW.
Ocean warming has contributed to longer and more frequent marine heatwaves. The increasing frequency of these heatwaves in NSW – and around Australia – has caused permanent impacts on marine ecosystem health, habitats and species. These impacts include:
- depleting abundance of kelp forests and sea grasses
- increased frequency and severity of coral bleaching
- shifting of some marine species away from the equator towards the north and south poles
- increasing occurrence of disease.
Marine heatwaves also have negative effects on NSW’s commercial fisheries and aquaculture.
The East Australian Current has extended 350 kilometres southward in its range of influence, making the southern waters warmer and saltier. As this continues, it will affect the exchange of water between the open ocean and inshore regions, and alter marine habitats. It will also influence nutrient supply and larval dispersal in inshore regions, affecting some marine species.
As the ocean warms around Australia, it is expected that the upper ocean will become more layered. This could result in a decline in the vertical supply of nutrients to the surface, reducing primary productivity. This will in turn affect marine productivity and fisheries, and marine animals such as turtles, sharks and seabirds.
Ocean warming is leading to fewer tropical cyclones, but they are expected to be more intense. Their frequency is also expected to vary more year to year. More intense tropical cyclones, which track southwards along the Queensland coast and into NSW, erode the coast and disrupt marine trade and international supply chains. Less beach sand as a result of erosion affects recreation, and participation in many community and cultural activities.
More severe tropical cyclones and temperate storms can also damage important ocean ecosystems such as kelp beds and cool water rocky reefs. These ecosystems provide important habitats and food sources for marine wildlife. Kelp beds also produce oxygen and absorb carbon dioxide.
Ocean acidification reduces the ability of calcifying organisms to produce their shells. This may have major ramifications for marine ecosystems, disrupting the food chain and affecting the commercial oyster industry.
As the climate warms, ocean water expands, contributing to rising sea levels. In addition, melting glaciers and ice sheets add water to the oceans, further increasing global mean sea level.
In its Sixth Assessment Report, the Intergovernmental Panel on Climate Change (IPCC) projected that global mean sea level is likely to rise by approximately 0.32 to 0.62 metres by 2100 under a low emissions scenario (SSP1-2.6), and by 0.63 to 1.01 metres under a very high emissions scenario (SSP5-8.5).
Sea-level rise will increase inundation of low-lying coastal and estuarine areas, including impacts on urban areas, stormwater systems and coastal properties. Higher sea levels will also increase coastal erosion and amplify the impacts of storm tides associated with east coast lows and tropical cyclones, leading to greater risks for coastal infrastructure and communities.
The NSW marine estate is home to unique and globally significant marine species including a diverse range of seaweed and cephalopods such as the giant Australian cuttlefish – the largest in the world.
The impacts of climate change are leading to a loss of some marine species in NSW. This is because climate change is altering the conditions that organisms and ecosystems are living in faster than they can adapt to such changes.
Globally, climate change is changing how the biosphere, atmosphere and hydrosphere interact with each other. This in turn affects environmental chemistry and upsets the balance in the oceans’ carbon and nutrient cycles.
Temperature drives the biology in the ocean. As warming reduces the density of water, it can lead to lower concentrations of nutrients in surface waters. This reduces levels of phytoplankton and zooplankton, which in turn reduces the numbers of fish that need this food source to survive.
Temperature also drives changes in the distribution of marine plants and animals, with most species moving towards cooler temperatures at higher latitudes.
Adapting to changes in the ocean in NSW
The most effective way of reducing the impacts of climate change on NSW's ocean is to reduce greenhouse gas emissions and thereby limit the level of climate change.
To help ocean managers consider climate change in their work, guidance is available on the climate-adapted ocean management page.
The NSW Government is taking action on climate change through multiple pathways, including the Climate Change (Net Zero Future) Act 2023, the NSW Climate Change Adaptation Strategy and the NSW Climate Change Adaptation Action Plan 2025–2029.
Related information
National Marine Science Plan 2015-2025 - National Marine Science Committee
Australian Seabed Mapping - AusSeabed
Ocean Decade - United Nations
Integrated Marine Observing System - IMOS
Marine Biodiversity Hub - National Environmental Science Program (NESP)
Marine and ocean - Australian Bureau of Meteorology
Case studies
On the New South Wales South Coast, a project bringing Aboriginal cultural custodians into the bushfire emergency control room is reshaping how decisions are made under pressure.
The Yass Area Network of Landcare Groups is is using the Restore and Renew webtool to guide seed selection for their Climate Ready Revegetation Project.
The Restore and Renew webtool provides simple, science-backed guidance to improve restoration projects across New South Wales. In the Hunter Valley, it is helping to rebuild climate-ready, genetically diverse populations of the River Red Gum.