By Maria Jose Castaneda.
Along the coasts of the world’s temperate and tropical oceans thrives a group of plants crucial in the fight against climate change: seagrass meadows. Although seagrasses are not as well-known as forests or jungles, these coastal ecosystems outperform their terrestrial counterparts in capturing and storing carbon, making them one of the most important tools we have to slow global warming.
Seagrasses are underwater plants found in shallow coastal waters around the world, stretching from the coasts of America, Africa, Asia, Australia, and Europe to the Arctic, except for Antarctica. But what makes these meadows so effective against climate change?
Although they may seem like unremarkable marine plants, seagrasses are true climate superheroes. Some seagrass meadows can store up more carbon than tropical rainforests and jungles combined. According to the Environmental Justice Foundation, some seagrass meadows can store up to 30 times more carbon than a tropical rainforest. The article “Seagrass Ecosystems as a Globally Significant Carbon Stock” published in Nature Geoscience revealed that seagrass ecosystems can store up to ≈ 83,000 metric tons of carbon per square kilometer surpassing the 30,000 tons stored by terrestrial forests to the ≈ 30,000 tons stored by terrestrial forests.
This biochemical process in which carbon is sequestered, assimilated, and stored in the oceans is known as “blue carbon.” Scientist and expert Christian Nellemann mentioned, “Just three habitats are really doing the heavy lifting: (1) seagrasses, (2) tidal marshes, and (3) mangroves,” highlighting the role of these three marine ecosystems in carbon capture and storage. Specifically, seagrass ecosystems have a superior capacity to sequester large amounts of carbon dioxide (CO2). An interesting fact is that although seagrass meadows cover only a minimal surface of the ocean floor, they are responsible for more than 10% of the carbon captured annually in the world.
Seagrasses are not only important for carbon capture; the meadows also play a key role in maintaining ocean balance and supporting marine life. An example of this is their roots and rhizomes, which stabilize sediments, thereby reducing coastal erosion. Additionally, they help filter pollutants and recycle nutrients, primarily phosphorus and nitrogen, thus improving water quality. In addition to being a source of organic matter, seagrass meadows provide shelter and food for a wide range of benthic invertebrates, fish, reptiles, and mammals.
However, despite their vital role in coastal and global systems, these ecosystems are in danger. Species such as Phyllospadix japonicus, Halophila engelmanni, Zostera capensis, Zostera caulescens, Zostera asiatica, Zostera caespitosa, Zostera marina, Zostera noltii, Posidonia oceanica, Halophila hawaiiana, and many other species are disappearing. The current status of many of these species is unknown due to the lack of studies monitoring seagrass meadows. In the database of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, many of these species are classified as “data deficient” or “unknown” because there is insufficient information to assess their situation. According to the Global Seagrass Observing Network, approximately 30% of the world’s seagrass meadows have disappeared, although this figure could be even higher. Factors such as pollution, coastal development, fishing, ecological degradation, navigation, and climate-related impacts have accelerated this loss.
In places like Biscayne Bay in South Florida, the deforestation of coastal habitats has led to the mass die-off of seagrasses. “The northern part of Biscayne Bay has gone through 60 years of seagrass loss. It’s difficult to tell you how much seagrass we’ve lost in Southern Biscayne Bay because, largely in Southern Biscayne Bay, we’ve changed species,” says Florida International University seagrass specialist Jim Fourqurean. “There’s almost immeasurable value to the protection we get from it for the real estate that’s built up to the shoreline. They are incredibly valuable ecosystems. They’re not just pretty.”
So, why isn’t there more talk about seagrasses if they play such an important role in the world? Part of the reason is that before the 1990s, there were few studies related to these plants compared to their terrestrial counterparts. Fortunately, in recent years, priority has been given to the study of marine plants like seagrasses, which were previously thought to have little importance in the fight against global warming. Nowadays, with the concept of blue carbon, the focus has shifted to plants like seagrasses, mangroves, tidal marshes, and certain macroalgae, as their role in carbon capture, coastal protection, and their critical function in marine habitats is undeniable.
In some parts of the world, efforts are being made to restore seagrass meadows and revive these ecosystems. In Wales (UK), the World Wildlife Fund (WWF) and Sky Ocean Rescue have been working with experts from Swansea University on restoration projects that involve dispersing seeds in areas where seagrass meadows once thrived. In Plymouth (UK), conservationists have founded a reforestation project in collaboration with the Royal Botanic Gardens Kew, Plymouth University, the Marine Biological Association, and Natural England, where large-scale seagrass meadow restorations are underway. In Africa, local communities in coastal regions are being engaged to educate people on the importance of conserving and restoring coastal ecosystems, including seagrasses. Meanwhile, in Indonesia, there are citizen science projects like “Seagrass Watch,” which involve continuous monitoring to track changes in the health of seagrass meadows.
Despite all the research and projects focused on these marine ecosystems, the future of seagrasses is uncertain. The drastic variations in environmental variables make it difficult for seagrasses to survive. Other factors, such as rising sea levels, increasing sea surface temperatures, and extreme weather events, degrade and destroy these critical habitats. Certainly, conservation efforts are few, and much remains to be done. Conservationists and scientists have called for greater protection of these organisms to ensure that seagrass meadows do not become extinct.
As the world confronts the negative consequences of climate change, seagrasses offer a ray of hope. The ability of seagrass meadows to capture, absorb, and store carbon is essential in the global fight to reduce carbon emissions. The future depends on us—on conserving and preserving our natural environment, the oceans, and with them, protecting these ecosystems before they disappear beneath the waves forever.