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Saving Earth's Oceans Could Offer One-Fifth of Needed Emissions Reductions

By Leslie Nemo
Sep 25, 2019 9:40 AMNov 18, 2019 5:49 PM
Earth’s oceans are a powerful tool when it comes to mitigating climate change, a new report argues. (Credit: NASA)


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A future where climate change is taken seriously everywhere — where batteries trump fuel tanks and forests stay intact — is easy to picture. But for too long, ideas of a sustainable planet have focused on what we can do on land, and not planned for what the ocean could help accomplish. 

That’s the argument put forth by the High Level Panel for a Sustainable Ocean Economy, a group of 14 heads of state from countries that are particularly reliant on the high-seas for their way of life. The right choices about how we use the ocean (and what parts we leave alone) could account for 21 percent of the emission reductions needed to limit global warming to 1.5 degrees C by 2050, according to a related policy forum in the journal Science. The authors say their proposal is the first in-depth, quantitative look at how the water that covers over 70 percent of Earth’s surface could mitigate climate change. 

“We are facing rapid climate change, and have got to find solutions,” says Ove Hoegh-Guldberg, director of the Global Change Institute and Professor of Marine Science at The University of Queensland. “But we haven’t realized many opportunities lie within the global oceans.” Those most beneficial options fit into five action categories, which Hoegh-Guldberg and his colleagues detail in the article published today. 

For one, nations will need to ramp up their marine-based renewable energy sources — tidal, wave and offshore wind power. How and where that aquatic machinery works must be planned to minimize impact on wildlife, which could one day mean developments operating far from the coast. Offshore wind farms in particular excite Hoegh-Guldberg, he says, because development in that area is already moving quickly.

The shipping industry will have to change too. Alternative power sources like batteries or fuel cells will eventually need to replace diesel, but for now, higher efficiency standards from organizations like the International Maritime Organization could push current and future ships to make the best use of the fuel they burn, the authors suggest.

We also can’t forget about the carbon-storing potential of our underwater forests. The soil surrounding mangrove, seagrass and other saltwater plants is so dense with organic matter, destruction of these watery ecosystems releases over five times as much CO2 per acre as does that of land-based forests. Maximizing carbon storage in these ecosystems requires keeping them healthy—something marine protection designations could ensure, so long as they’re well-enforced. 

A changed relationship with the ocean will also impact how we eat. Many seafoods lead to fewer emissions than land-based animal proteins, the authors say. While convincing more people to swap burgers for filets sounds intimidating, this pivot would be a low tech way of reducing food-based emissions.

The final option — and admittedly, the authors say, the one that needs the most research — is storing carbon emissions in seabeds. In theory, this mitigation tactic would involve injecting CO2 into ocean floors and trapping it. Related experiments are underway in Norway and Texas. More research will determine how these injections impact wildlife and other ecosystems, Lubchenco and colleagues say.

Some of the 14 countries behind this report have already announced ocean-based climate change plans. Mexico plans to establish another 100,000 hectares of sustainable fishing areas and designate another 31 fishing refuge areas. Fiji promises to make their shipping industry carbon-free by 2050. 

For the ocean to help us meet our 2050 goals, other nations also need to build and stick to timelines for completing some of the strategies, the authors say. A prime time to do this might be 2020, they recommend, when countries in the Paris Agreement have a chance to update their five and 10-year goals.

Some of these strategies are simply a matter of implementation, says Hoegh-Guldberg, and others need plenty more research. But many just need a little more preparation and understanding before governments can make them a reality. “That is where ambition comes in,” he says.

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