Kelp Can Help: Kelp Forests Reveal Hidden Potential for Blue Carbon Sequestration

Dana Roeber Murray via flickr

Kelp Can Help: Kelp Forests Reveal Hidden Potential for Blue Carbon Sequestration

Blue carbon is the organic carbon that is captured and stored in coastal vegetated ecosystems. Most blue carbon budgets focus on tidal salt marshes, seagrass meadows, and mangrove forests. A new study looks to the once overlooked “hidden forests” of kelp to quantify its blue carbon potential. 

Filbee-Dexter, Karen, and Thomas Wernberg. “Substantial blue carbon in overlooked Australian kelp forests.” Scientific Reports 10.1 (2020): 1-6. 

In the face of global climate change, carbon stocks and flows attract attention from all corners of climate policy. Carbon sequestration - the long-term process of capturing and storing atmospheric carbon dioxide - occurs through a series of biological, chemical, and physical processes. We increasingly rely on terrestrial ecosystems, such as old-growth forests, to store organic carbon. However, coastal vegetated ecosystems, such as tidal salt marshes, seagrass meadows, and mangrove forests also store carbon dioxide in the form of blue carbon. Noticeably missing from this list is kelp – the ocean’s “hidden forests” of macroalgae. A new study reveals that kelp forests can contribute to substantial carbon sequestration and could be considered a key ecosystem within global blue carbon budgets. 


Scientific interest in quantifying blue carbon stocks and flows has helped to shed light on the significant role of coastal ecosystems in sequestering organic carbon. In a recent study published in Scientific Reports, Dr. Filbee-Dexter and Dr. Wernberg of the University of Western Australia highlight the vital role of kelp forests in mitigating climate change. Their study combined areal extent mapping, biomass calculations, and productivity measures across the entire Great Southern Reef to quantify the total blue carbon sequestered in Australia. 

This study revealed that kelp forests in Australia sequester approximately 1.3-2.8 teragrams of carbon per year. Thus, kelp forests account for 30% of the total blue carbon sequestered annually in Australia, and about 3% of the total global blue carbon budget. These measurements have immense implications for Australia’s total carbon budget. Most importantly, the results suggest that by omitting kelp forests, blue carbon accounting significantly underestimates carbon sequestration potential. Moreover, these findings urge scientists to create more accurate blue carbon budgets that include the “hidden forests” of kelp. A better assessment of the world’s blue carbon budget will help to raise awareness about the multitude of co-benefits of coastal ecosystems, including their role in sequestering carbon and mitigating climate change. 


Unfortunately, kelp forest decline is projected to increase as global sea temperatures and atmospheric temperatures rise. Human-caused environmental stressors such as coastal development, poor water quality, coastal pollution, climate-induced marine heatwaves, and drought also affect the health of kelp forests. As a kelp forest deteriorates, it releases sequestered carbon dioxide back into the atmosphere, and the kelp forests become a source of carbon rather than a sink. The decline of kelp forests globally includes not only the loss of critical carbon sequestration potential, but also the loss of beneficial ecosystem services, such as habitat for species, primary production, and nutrient cycling. 


Dr. Filbee-Dexter and Dr. Wernberg’s work raises awareness about the critical role of kelp forests in blue carbon budgets. Encouragingly, blue carbon has garnered the attention of regional and international environmental managers and policy makers due to its ability to help countries mitigate and adapt to global climate change. Valuing kelp forests as blue carbon ecosystems provides a promising opportunity in climate change mitigation. Increased monitoring of kelp forests will support our understanding of these ecosystems and their resilience to global climate change. Continued conservation and restoration of all coastal ecosystems will help to minimize the losses of these valuable global blue carbon stocks 


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