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Combating Ocean Acidification and Climate Change with Underwater Forests

Emily Heaslip

Today, the acidity of the ocean is greater than at any point in the past two million years. Ocean acidification is one of the biggest effects of climate change, leading to coral bleaching, preventing organisms from growing shells, and contributing to toxic algae blooms. 

Recently, scientists have discovered a new, low-risk intervention that can help reduce the impact of ocean acidification. Research shows that certain types of marine vegetation act similarly to forests on land. Trees take carbon dioxide (CO2) from the air and help the soil capture significant amounts of carbon. Reforestation has shown to be an effective strategy for carbon capture — and the same is true for ocean ecosystems, too. 

Planting underwater forests could have the same impact on the ocean as reforestation on land. But, kelp forests alone won’t restore the health of the ocean; human behavior change is needed to ensure these interventions are successful. 

How bad is ocean acidification?

Ocean acidification is a process by which the pH of the ocean is reduced over an extended period of time as carbon dioxide in the atmosphere increases, making the ocean more acidic. 

“When CO2 is absorbed by seawater, a series of chemical reactions occur resulting in the increased concentration of hydrogen ions. This increase causes the seawater to become more acidic and causes carbonate ions to be relatively less abundant,”  explained NOAA.

Ocean acidification has worsened dramatically over the last century; the pH has dropped by 26% to become more acidic — putting marine ecosystems in crisis. Acidification particularly impacts shellfish and coral reefs — organisms that need carbonate ions to make their shells and skeletons. When these populations struggle, delicate ocean ecosystems also begin to fail. 

Combating ocean acidification & climate change

The only permanent way to reduce the risk of ocean acidification is to reduce our carbon emissions. However, researchers have also found that kelp, eelgrass, and other marine vegetation can help effectively absorb CO2 and reduce acidity in the ocean. 

Studies in the Florida Keys, Indo-Pacific, Oregon, and Maine have all shown that seagrasses, kelps, and shell beds might be able to counteract ocean acidification. One project in the Indo-Pacific showed that seagrass meadows should give corals about an 18% boost in growth

“The reason is the banks of seagrass growing in Florida’s inshore waters, like turtle grass and manatee grass, that suck up CO2 as they photosynthesize — particularly in the spring,” wrote researchers at the Yale School of the Environment. “Plants in the ocean, from seagrasses to plankton, add up to just 0.05 percent of the plant biomass on land, but are so pervasive and efficient at sucking up carbon that they cycle through roughly the same amount of carbon every day as all the land-based plants.”  

In comparison to other proposed interventions to reduce acidity, these interventions are low-cost, low-risk, and offer the ancillary benefit of providing a refuge for organisms in the ocean, boosting ecosystems in myriad ways. 

Planting underwater forests to reduce the impact of climate change

Larger-scale studies are currently underway to assess the scalability and potential impact of underwater forests. Scientists warn, however, that simply planting more marine vegetation isn’t enough. 

One-third of the world’s seagrass has been lost since the 20th century; this decline is due to a number of human activities. Shipping vessels uproot and destroy seagrass when they drag against the ocean floor. Pollution, channel deepening activities, and other underwater drilling reduces the amount of light that seagrass needs for photosynthesis. And, pandemic disease has further decimated seagrass, making it one of the most at-risk ecosystems in the world. 

Seagrass is challenging to restore, which is why scientists are also examining the efficacy of other marine plants, such as kelp. Kelp forests have promising implications for the human population, too. As a major ingredient in Asian cuisine, kelp forests could provide the dual benefit of carbon removal and source of food and income for farmers, provided harvesting happens after the carbon is removed from the ocean. 

Ultimately, the success of underwater forests in combating climate change and ocean acidification depends on human behavior change. We need to not only emit less carbon but take better care of ocean health. By reducing pollution, we can begin to restore these valuable ecosystems that play a vital role in maintaining the health of our planet. 

Learn more about climate change and how it impacts our oceans on the Sofar Ocean blog.

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