Kelp Could Be One of the Lone Sea Plant Survivors of Climate Change

Kelp forests, swaying gently under the waves, are robust ecological zones. The plant—technically a macroalgae—can grow up to two feet per day, forming the basis of critical fish, crustacean, and marine mammal habitat and providing coastal storm protection to the tune of billions of dollars each year.

Fears of kelp forest die-offs have risen as warming ocean temperatures have been shown to affect other ocean plant species such as corals and sea grasses. But a new study analyzed kelp health at 1,138 places around the globe and found that many kelp stocks have remained nearly stable and in some places are increasing despite global warming.

The study, published Monday in the Proceedings of the National Academy of Sciences, reports that while kelp in 38 percent of the regions tested show clear declines, 27 percent show increases, and 35 percent show no net change.

Fiorenza Micheli, a marine biologist at Stanford University and coauthor of the paper, said she was surprised at the results.

“In Baja California where I work, I have seen the deforestation of the kelp with warm temperatures we’ve seen this year, so I expected worse,” Micheli said. “This also brought home why we need to do global monitoring.”

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Kelp may have outsize benefits in battling a warmer world. In recent years, scientists have stressed the benefits of blue carbon—carbon dioxide that has been captured and sequestered by living marine organisms. Of all the carbon captured in the world, 55 percent is captured by marine life.

Dorte Krause-Jensen, a senior scientist at Aarhus University in Denmark, says that seaweed farming could be a way to store carbon. “The climate mitigation benefits of seaweed farming are overlooked,” she said, adding that farmed seaweed could be used as a biofuel substitute for fossil fuels.

Kelp is found on every continent except Antarctica, and the species has a remarkable ability to survive in the face of environmental stresses and threats. Still, Micheli explained that increasing water temperatures and more frequent storms will have negative impacts. Warmer water holds fewer nutrients, so the species can’t grow as fast or as big as it might otherwise. Storm surges can wipe out entire forests—especially if their growth is stunted. In addition, sea urchins overgraze kelp in some places, though the reintroduction of sea otters and their voracious appetites to marine ecosystems have been shown to keep sea urchin populations in check and benefit kelp growth.

The study authors said that local conditions often dictated how kelp were faring. For example, when the species was facing threats from coastal development, fishing, and pollution, kelp forests were more likely to be in decline.

Bringing together more than 1,000 kelp surveys throughout the world required some innovative partners. In Baja, a Mexican nonprofit called COBI (Comunidad y Biodiversidad) trained local fishers to scuba dive and conduct surveys of what they found in the coastal seabed—not just kelp but also sea cucumbers, abalone, and the rest of the ecosystem. Micheli said the data gathered by these fishers was just as robust as data gathered by scientists.