Blue carbon ecosystems are critical habitats that store large amounts of carbon. As a result of anthropogenic activities, these habitats have degraded, releasing carbon dioxide and exacerbating the rise of greenhouse gas emissions.
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Therefore, current and future policies hope to restore and protect such systems in the hopes of mitigating the effects of climate change, yet many elements of blue carbon research remain unclear.
The Blue Revolution as a Response to Emerging Environmental Issues
Amid a changing climate and shrinking agricultural productivity, the search for alternative food production methods and climate mitigation has been of utmost priority for global institutions.
Emerging as a prime candidate has been the use of marine and freshwater areas that provide opportunities for aquaculture and blue carbon sequestration. As a result, the blue revolution has rapidly accelerated in recent years, with a growing socioeconomic interest focusing on blue spaces and resources.
In particular, blue carbon has been pushed as a promising solution to offsetting and addressing the rise of greenhouse gas emissions. Blue carbon was first coined a decade ago, referring to the carbon captured by the ocean and coastal ecosystems and is held in biodiverse systems such as seagrass meadows, mangroves, salt marches, and sand flats. The carbon sequestration mechanism operating in these systems is one of “capture and hold”, and habitat degradation is directly interfering with such sequestration.
Many systems have indeed lost the capacity to capture and hold carbon as the loss of key species and structures has contributed to a reduced carbon sequestration ability. Primarily, losses in mangrove coverage, the rise of urbanized shorelines, and the loss of coral reefs all contribute to such changes. However, the definition of blue carbon can sometimes be unclear.
The history of blue carbon was reviewed by Lovelock et al., in 2019. Here, authors discuss how blue carbon often refers to different concepts: (1) all organic matter captured by marine organisms, and (2) how marine ecosystems could be managed to reduce greenhouse gas emissions and thereby contribute to climate change mitigation and conservation. The study clarifies the multifaceted concepts associated with blue carbon and advocates for the need to standardize definitions should be established before developing broader climate change mitigation strategies focused on blue carbon.
Nonetheless, another 2019 study by Macreadie et al., presents how blue carbon has reached international prominence as a strategy for climate change mitigation due to its benefits. Specifically, the authors highlight that blue carbon strategies aim to offset climate change effects by increasing carbon storage while achieving improved coastal protection and fisheries enhancement. This is because blue carbon strategies also focus on restoration initiatives of ecologically significant species, such as mangroves, seagrass, or corals.
Therefore, blue carbon has gained interdisciplinary interest from diverse stakeholders like governments and intergovernmental bodies that are committed to marine conservation and climate change mitigation. However, despite the considerable momentum of campaigns, the future of blue carbon remains unclear. Knowledge gaps, ranging from clear definitions to applied case studies, are required before informing and implementing broader policies.
The Potential for Blue Carbon Strategies in Future Ecosystems
The future of blue carbon appears promising, with growing momentum and interest in blue carbon strategies, primarily due to the interconnectedness of blue carbon with Sustainable Development Goals (SDGs). For instance, blue carbon is closely associated with coastal habitat conservation, and protecting such systems allows for habitat preservation and better carbon storage.
In turn, blue carbon strategies not only benefit coastal habitats but also provide better ecosystem services, recreational opportunities, storm protection, and nursery habitat for commercial and recreational fisheries.
Therefore, understanding which ecosystems to focus on and protect is particularly valuable, as this would increase the effectiveness of blue carbon strategies. This was considered by Taillardat et al., 2018, who reviewed carbon sequestration rates within key ecosystems.
Findings show that blue carbon ecosystems are the most efficient natural carbon sinks at the plot scale, yet certain aspects of blue carbon remain unclear. For instance, many processes in models appear overestimated. In 2014, coastal habitats buffered only 0.42% of the global fossil fuel carbon emissions. However, when examining finer spatial scales, this rate increases, with > 1% of carbon emissions mitigated in countries such as Bangladesh, Colombia and Nigeria. Therefore, addressing varying effectiveness across spatial scales is a key consideration when defining strategies related to policy-makers' requirements.
Implications and Limitations for the Future of Blue Carbon
Research trajectories considering blue carbon ecosystems have gradually improved our understanding; however, certain limitations persist in blue carbon research. In a 2021 study, Macreadie et al. compared the capacity of different blue carbon ecosystems (i.e., mangrove forests, seagrass meadows and tidal marshes) to store carbon. The authors reviewed existing literature on each system and found habitats have differing capacities to store carbon.
Findings showed that blue carbon ecosystem restoration has been estimated to 0.2–3.2 million ha for tidal marshes, 8.3–25.4 million ha for seagrasses and 9–13 million ha for mangroves, which could draw down an additional 841 Tg CO2 per year by 2030, collectively amounting to ~3% of global emissions. Across habitats, mangroves provided provide the greatest carbon-related benefits, and could be the focus of key policies targeting blue carbon ecosystems.
However, the study points out that the degradation of blue carbon ecosystems is unlikely to stop and that a better understanding of other blue carbon ecosystems is urgent and of significant conservation, social, and economic interest. Moreover, many losses already incurred in systems are likely irreversible, and only certain areas may be suitable for restoration.
These limitations were echoed in a 2022 study by Lai et al., who discussed how blue carbon research remains uncertain in its applications and restoration capacity. Authors analyzed 908 articles considering the response, restoration and protection of blue carbon ecosystems and found that research remains largely unclear and not well standardized. As a result, authors across studies are advocating for better communication and stronger research to improve our understanding of blue carbon ecosystems.
Ultimately, the future effectiveness of restoring blue carbon ecosystems to mitigate the effects of climate change may rely on research efforts considering spatiotemporal complexities and the applicability of different policies. In turn, this may improve the resilience of habitats, bolster the provision of critical ecosystem services, and enhance the benefits derived from habitat protection to local communities.
References and Further Reading
Lai, Q., Ma, J., He, F., Zhang, A., Pei, D., Wei, G., & Zhu, X. (2022). Research Development, Current Hotspots, and Future Directions of Blue Carbon: A Bibliometric Analysis. Water, 14(8), p. 1193. https://www.mdpi.com/2073-4441/14/8/1193
Lovelock, C. E., & Duarte, C. M. (2019). Dimensions of Blue Carbon and emerging perspectives. Biology Letters, 15(3), p. 20180781. https://royalsocietypublishing.org/doi/10.1098/rsbl.2018.0781
Macreadie, P. I., Anton, A., Raven, et al. (2019). The future of Blue Carbon science. Nature Communications, 10(1). https://www.nature.com/articles/s41467-019-11693-w
Macreadie, P. I., Costa, M. D. P., Atwood, et al. (2021). Blue carbon as a natural climate solution. Nature Reviews Earth & Environment, 2(12), pp. 826–839. https://www.nature.com/articles/s43017-021-00224-1
Taillardat, P., Friess, D. A., & Lupascu, M. (2018). Mangrove blue carbon strategies for climate change mitigation are most effective at the national scale. Biology Letters, 14(10), p. 20180251. https://royalsocietypublishing.org/doi/10.1098/rsbl.2018.0251