The oceans do a lot to support life on Earth, including bearing the brunt of global temperatures that have continued to warm for decades.
An IPCC special report published in 2019 found that the oceans – which make up more than 70% of the world’s surface – have absorbed between 20% and 30% of man-made carbon dioxide emissions since the 1980s. They are also responsible for absorbing more than 93% of “the combined heat stored by warm air, sea, and land, and melting ice” since the 1970s, according to the Fifth Assessment report published in 2013 by the United Nations Intergovernmental Panel on Climate change.
The tipping point is imminent, experts told ABC News. But there are collective actions that can be taken that can revitalize the oceans to a healthier state — the theme of the 2022 UN World Oceans Day.
“We really see the oceans as the biggest ally in the climate change crisis,” Lea d’Auriol, founder of the nonprofit Oceanic Global, told ABC News.
Here’s how climate change affects the health of the world’s oceans:
Species faced with adapting or going extinct
Today, the oceans are “in a state of imbalance” that has nearly doubled since the 1990s, d’Auriol said. Look no further than the fishermen, who feed the more than 3 billion people who rely on seafood as their main source of protein, as witness that climate change is already here, says d’Auriol.
“If you want to ask someone if climate change is really happening, probably the surest answer you’ll get from anyone other than scientists is fishermen,” Arlo Hemphill, senior marine campaigner for Greenpeace USA, told ABC News. “Because the fishermen see these things happening in real time.”
One of the changes that longtime fishermen are witnessing is the presence of a new species venturing north as the area expands with their preferred water temperature.
Marine organisms maintain the same temperature as the surrounding water, so as temperatures increase, organisms’ temperatures also increase, Martin Grosell, professor of ichthyology and chair of the University of Miami’s Department of Marine Biology and Ecology, told ABC News. As temperatures rise, organisms need more energy to move and survive. But, on the other hand, oxygen levels in the water decrease as temperatures warm, forcing species to move, Grosell said.
Such migrations may seem harmless, but they disrupt ecosystems around the world, such as the phenology, or timing, of gray seals giving birth, Hemphil said.
Instead, species continue to die out due to repeated events of oceanic heatwaves, Anne Christianson, director of international climate policy for the Center for American Progress, a public policy research organization, told ABC News.
Coral reefs are among the world’s most threatened marine ecosystems, scientists say. Coral bleaching, a process that occurs when water is too warm and algae expels corals from their tissues, causing them to turn completely white, is occurring at an “alarming” rate — increasing at a rate of 4% per year — along with increasing mortality rates across the region. , said d’Auriol.
A study published in the National Academy of Sciences found that coral reefs could stop growing in 10 years unless greenhouse gases were significantly reduced and, in the worst case scenario, 94% of all reefs could be eroded by 2050.
Coral reefs are often an indicator of ecosystem health, Brenda Ekwurzel, director of climate science for the Union of Concerned Scientists, told ABC News.
Mammals that depend on Arctic ice, such as polar bears and ringed seals, one of the main food sources for polar bears that live their lives almost entirely on ice, are also under threat, Ekwurzel said.
Vegetation such as mangroves, seagrass and swamps, some of the largest carbon sinks on the planet, which absorb and store carbon dioxide from the atmosphere, are also at risk of extinction, d’Auriol said.
The number of dead zones increased
Dead zones, or hypoxic processes, occur when algae suck up all the oxygen in an area, making it impossible for marine life to survive — essentially biological deserts, according to the National Oceanic and Atmospheric Administration.
A study published in 2008 in Science found that there are 400 dead zones worldwide. By 2019, the number of dead zones had risen to about 900, d’Auriol said.
Dead zones often occur in areas with rampant nutrient runoff, such as at the bottom of the Mississippi River, where it empties into the Gulf of Mexico, Hemphill said.
Sea level rise will change coastal communities
The biggest contributor to sea level rise is melting Arctic ice, which is warming twice as fast as the rest of the world, according to the 2021 Arctic Report Card by NOAA. The increase in sea level rise of 6 inches to a foot since the Industrial Revolution may seem like a small increase, but critical infrastructure near the oceans isn’t built to hold the extra inches of water, experts say.
Millions of people living on coastlines around the world, including in major cities such as New York, Los Angeles and San Francisco, will be displaced by rising sea levels, d’Auriol said.
Carbon dioxide emissions trigger ocean acidification
Ocean acidification, which occurs when the pH level of water is lowered as a result of carbon dioxide in the atmosphere, is not directly caused by warming temperatures but rather by excessive carbon dioxide emissions, Hemphil said.
“The worrying thing is that all shellfish from microscopic plankton, to clams and crabs and coral reefs themselves use calcium carbonate to build their shells,” he said. “And as the oceans are acidified, it becomes more difficult to make shells.”
Ocean acidification, not coral bleaching, is likely to be the culprit behind coral reef deaths, Ekwurzel said.
Collective action is needed to protect the oceans
In line with the 2022 theme for World Oceans Day, “Revitalization: Collective Action for the Oceans,” scientists and conservationists highlight the need for individuals, communities, non-profit organizations, the private sector, and governments to come together to create solutions, d’Auriol said.
This includes ensuring the health of marine protected areas by eliminating surrounding housing, fishing zones and shipping traffic, d’Auriol said.
Governments need to come up with policies to protect human life and marine health, Christianson said.
“There is not a single silver bullet to solving this crisis at sea and on land,” Christianson said.
However, the ticking time bomb is a race to drastically reduce global greenhouse gas emissions in the next decade, experts say.
“We cannot delay the solution any longer,” said Ekwurzel.
Along the way to properly protecting and conserving the oceans, dispelling the narrative that the oceans are an environmental issue separate from climate change and biodiversity conservation, d’Auriol said.
“Because we do live on a water planet, and this planet is responsible for sustaining all life on Earth,” he said.