The ocean and climate change

The ocean provides crucial protection against the full effects of climate change, removing carbon from the atmosphere, absorbing heat from carbon emissions, and protecting our coasts from erosion and storm damage. We must protect this superhero.

Absorbing and storing carbon

The ocean captures and stores around 25% of the CO2 we release into the atmosphere and absorbs 90% of the heat produced by emissions – which is crucial in these times of ever-increasing CO2 levels.

Marine habitats like seagrass meadows, kelp forests, coral reefs, and seaweed are vital carbon stores, much like forests on land. Even more so, in fact, with seagrass meadows alone estimated to absorb and store 35 times more CO2 than rainforests. Seaweed absorbs carbon more effectively and produces more oxygen than trees, storing an estimated 175 million tonnes of carbon each year.

We also know that the offshore environment in deep water sands and muds is the biggest store of carbon in the UK environment – with up to £1 billion worth of carbon storage in our deep-sea areas.

By removing carbon from the atmosphere and keeping it locked down, the ocean and its habitats help lower CO2 levels and protect us from rising temperatures, slowing down climate change and preventing us from experiencing its full impacts.

Coastal protection

Seagrass beds, coral reefs, mangrove and kelp forests also prevent and reduce coastal erosion – something which is on the rise due to climate change. By lessening the impact of waves and strong currents, these ocean superheroes provide coastal communities with vital protection from erosion and flood and storm damage.

These coastal habitats aren’t just valuable to communities, but to the economy too. In the UK alone, they save up to £33.2 billion pounds compared to the cost of man-made alternatives.

Seaweeds and seagrasses are also important for stability - seaweeds which end up on beaches release nutrients into dune habitats, which helps stabilise and protect sediments, while seagrasses lock the sandy seabed together, offering exposed coasts further protection from erosion.

Renewable energy

The ocean can also help us achieve Net Zero and give us the best chance of combatting climate change by generating renewable energy, and the UK is looking to its marine areas to deliver this by 2030. By adding offshore wind, tidal and wave energy to the UK’s energy mix, we can shift towards clean energy and reduce our reliance on damaging fossil fuels which accelerate global heating and CO2 emissions.

However, shifting towards clean, renewable energy must not be at the expense of nature, and we need to protect and conserve the life beneath the waves giving us power. We need to minimise the impacts of offshore infrastructure on marine ecosystems and species, such as noise disturbances, collision risks and physical damage to the seabed.

We need renewable energy to tackle climate change. But it must be done in a nature positive way, underpinned by robust marine planning and environmental assessments that informs environmentally conscious construction.

Reducing our consumption of and reliance on fossil fuels should result in less pressure placed on our ocean, allowing it to continue to protect our coasts, absorb and store carbon, and help us fight climate change. But it must be healthy to do so and we need to ensure that we do not put more pressure on these vital ecosystems. We need investment to protect and restore our ocean, which is being harmed in the process of protecting us.

Rising temperatures

Ocean temperature is a key indicator of climate change, with 90% of global warming occurring in the ocean. Temperatures have been increasing since records began in 1995, with 2023 bringing the highest ocean temperatures ever recorded.

As sea temperatures rise, so too does the risk of losing our marine and coastal ecosystems, with many marine species sensitive to even slight changes in ocean temperature.

Heatwaves of 3-4°C in tropical countries have been causing significant coral death at regular intervals since 1998, and our surveys in Maldives are finding a lower abundance, complexity and diversity of coral reefs due to repeated ocean warming. Even short heatwaves have led to catastrophic losses of seagrass habitats, fish, and impacting the long-term survival and reproduction rates of dolphins.

Some marine species are moving further north to cooler waters, such as those on the west coast of the USA, whilst our most impressive predatory fish are having to hunt in a reduced oxygen environment caused by ocean warming in the upper areas of the ocean.

Changes can be seen in populations, too. Temperature determines the sex of turtles, with warmer temperatures resulting in females developing. We’re now seeing more female turtle hatchlings in tropical beaches, because of the sand being too hot for males during developmental phase.

If ocean heating trends continue, more than half of the world’s marine species may be on the brink of extinction by 2100. Vital habitats such as kelp forests, seagrass beds and oyster reefs will deteriorate further and could eventually die-off, sponge beds and other coastal species won't be able to filter our seawater, removing pollutants, and a warming of 1.5°C threatens to destroy 70-90% of coral reefs.

Rising sea levels

Every year, the sea rises another 3.2mm, and by 2050, it’s projected to rise by 30cm. Rising sea levels are caused by ice and glaciers melting and the fact that water expands as it gets warmer - so as the sea temperature rises, so does the level.

Coastal erosion caused by rising sea levels leads to habitat loss, for both marine life and coastal communities. Species which live or depend on beaches are impacted, with more saltwater on the shores disrupting important ecosystems like salt marshes. Changes to the enzymes and mineralisation in soil in the ecosystem leads to the loss of different plant species, with wildlife on beaches also impacted by the rapid changes to the environment.

Ocean acidification

When the ocean absorbs carbon dioxide from the air, the carbon reacts with the water, making it acidic. As more carbon dioxide is released into the atmosphere, the ocean absorbs more, making it increasingly acidic.

Ocean acidification leads to lower pH levels in the water and can reduce calcification in seaweeds, which can affect their ability to grow, photosynthesise and compete for food, water, and space.

Acidic water also caused marine organisms’ shells and skeletons made from calcium carbonate to dissolve – the more acidic, the faster they dissolve. This means animals such as corals, sea urchins, starfish, corals, oysters and mussels, have to spend extra energy repairing or thickening their shells and exoskeletons.

Storms

Our climate is becoming wetter and stormier, and most climate projections suggest that this will continue to be the case. This will undoubtedly impact our seas and those living in it, as well as coastal communities.

The powerful waves brought by storms damages vital marine habitats like seagrass beds, impacting their ability to absorb carbon, stabilise the seabed, and act as feeding and breeding grounds for marine life. There will also be a monetary cost, as there will be an increasing need to invest in man-made defences such as seawalls to protect our coastline from storm damage instead.

Extreme weather events caused by climate change, such as storms and floods, increase the amount of plastic and chemical pollution entering the ocean through sewage discharges and flood waters. Untreated sewage, chemicals and plastic pollution all harm wildlife and make them less resilient to the impacts of climate change, whilst also damaging the vital habitats that could help us buffer the impact of climate change.

Why we must protect our ocean

The ocean is one of our greatest assets and best chances at combatting climate change and its impacts – but our seas are also facing these impacts. It’s more important than ever to protect, conserve and restore our ocean and its vital ecosystems, so it can continue to provide the countless benefits it brings people, wildlife, and planet.

We're striving to raise awareness, carry out research and work with governments to bring about meaningful change. Will you join us?