Climate change and our oceans
The importance of oceans
We would have lived on a much warmer and less vibrant Earth If not for the oceans. Oceans absorb about 25% of emitted CO2 and more than half of the sun’s radiation, mediate temperature and regulate global climate in the process.
- Oceans cover 71% of the Earth’s surface and are home to an estimated 2 million species.
- Marine biodiversity is rich with an estimated 91% of species in the oceans yet to be discovered, catalogued or described.
- Oceans provide more than half of the oxygen we breathe.
- Fishing is the principal livelihood for over 200 million people and the main source of protein for more than a billion.
How are oceans affected?
Global warming is melting glaciers and causing thermal expansion of water. Scientists predict that sea levels may rise as much as 80 centimetres by 23001, and seven metres if the Greenland ice sheet melts completely2. Rising sea levels have serious impact on marine ecosystems by reducing the amount of sunlight reaching offshore plants and algae, as well as flooding coastal habitats such as mangroves.
Since the Industrial Revolution, ocean pH (a measure of its acidity) has dropped from 8.21 to 8.10, which makes it harder for fish, squid and other marine animals to extract the oxygen, and for shellfish, crabs, lobsters and corals to build calcium carbonate shells. In some cases, ocean acidification can cause their shells to dissolve.
Global fisheries are severely affected in the face of the accumulated impact of acidification, rising temperatures and coral bleaching, with fish catch in the tropics expected to drop up to 40% by 2050.
Impacted habitats and species
Climate change can aggravate environmental threats, increase biodiversity loss and even cause extinction.
Coral reefs are particularly in peril because high water temperatures and acidification can lead to massive bleaching and possibly their eventual death. They are important habitats and home to more than 25% of marine species in the world, including 4,000 fish species and 700 types of coral. In the past 30 years, half of the planet’s coral reefs have been lost as a result of climate change.
The changing climate also affects the metabolism, life cycle and behaviour of marine species. One of them is the marine turtle, whose sex is determined by temperature. A warmer nest can result in more females, thereby skewing their sex ratios and threatening population survival. As climate change worsens, cold water fish species are moving further towards the poles to find habitats with optimal temperatures. Those that do not adapt to the fast changing environment, may face extinction.
Climate change poses a fundamental threat to the human and animal life. We have set the following goals for 2030:
WWF is engaging policy makers, leading businesses and every citizen to address the consequence of global warming, which we are already experiencing. You can help turn the tide of biodiversity loss and help our ecosystems adapt to change, by:
1 Intergovernmental Panel on Climate Change (2007). IPCC Fourth Assessment Report: Climate Change 2007.
3 World Wildlife Fund (2018). How climate change is turning green turtle populations female in the northern Great Barrier Reef.
4 Proceedings of the National Academy of Sciences of the United States of America (2009). Ocean acidification impairs olfactory discrimination and homing ability of a marine fish.