A kelp forest Photo by Oleksandr Sushko on Unsplash

by Kristen Kessler. Kristen has a background in elementary education, and has been an environmental activist for several years.

The oceans are fighting a daunting battle against climate change. As the amount of atmospheric  carbon dioxide (CO2) increases, the oceans are burdened with the task of having to absorb increasing quantities of CO2. The oceans have absorbed 93% of the excess heat from  greenhouse gas emissions since the 1970s. Rising levels of carbon dioxide accelerate acidification of ocean water. The pH level of the water increases, and less carbonate is available for crustaceans such as shrimp and abalone to build strong shells. Crustaceans play an important role in balancing the ocean’s food web.

In order to make the oceans more resilient to climate change, they need to absorb and sequester more CO2. One way to do this is to restore carbon-sequestering marine ecosystems. Just like plants and trees on land, marine species, such as kelp, seagrass, and mangroves, absorb CO2 to carry out photosynthesis. In fact, they can absorb 20 times more carbon than their terrestrial counterparts. However, populations of marine plants—along with kelp, a type of macroalgae—have been severely depleted in recent years. From 2014 to 2016, a marine heatwave off the coast of California destroyed 90% of the state’s kelp forests.

A kelp forest Photo by Oleksandr Sushko on Unsplash

A kelp forest. Photo by Oleksandr Sushko on Unsplash

While restoring all types of sea plants and macroalgae is vital to ocean health, restoring kelp has added benefits. Kelp is especially effective at not only absorbing atmospheric CO2, but also in sequestering it—preventing carbon from getting released when it dies. When kelp dies, most of its biomass gets carried out to the open ocean. Eventually, its nodule-like structures release gasses, causing the kelp to sink. When it gets to the bottom, it gets buried in sediment. The carbon it gives off as it decomposes is sequestered in the sediment and remains there permanently. 

Kelp’s carbon sequestration ability has attracted the attention of researchers and entrepreneurs.  The latter are hoping that sequestering kelp on a large scale could be a solution to the climate crisis. 

One such company is Pull To Refresh. Its CEO, Arin Crumley, is looking to grow kelp on a massive scale to sequester carbon. His idea is to transport billions of tons of kelp to the open ocean in small vessels. The kelp would grow from trellis-like structures attached to the boats. It would absorb carbon during its lifetime, and then sink at the end of its lifespan. In theory, billions of tons of carbon could be sequestered, getting us back to pre-industrial levels of CO2. If companies like Pull To Refresh are successful, they will be able to sell carbon offset credits to corporations who are eager to purchase them. 

Wil Burns, a visiting professor at Northwestern University, is skeptical. He says that adding billions of tons of kelp to the oceans could have negative consequences. It could potentially disrupt migration patterns and alter the food chain. Species who attach themselves to the vessels could be transported far from their native habitats. Also, kelp thrives in cold, shallow waters. There is no guarantee that it will thrive wherever it is placed. 

Other scientists have weighed in as well. John Beardall, professor emeritus at Australia’s Monash University, says that sequestering kelp could be part of the solution, but is not going to be a “major route.”

In the meantime, there is certainly no debate that kelp forests should continue to be restored in their native habitats. Kelp restoration projects are occurring in several areas along the California coast. Notably, the Bay Foundation  has restored 56.88 acres of kelp forest in the Santa Monica Bay. A restoration project off the coast of Orange County was so successful that its focus has shifted to restoring green abalone. Additional restoration projects are underway in Mexico, Australia, and the United Kingdom.

The task of restoring the world’s kelp ecosystems is a long way from completion, but is off to a promising start. As long as these projects continue, there is reason to be optimistic about the future of these underwater forests, and through them, the future of our oceans.

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