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Stacey Trevathan-Tackett

blue carbon

Securing a future for Seagrass Meadows

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I have known and worked with Dr Peter Macreadie for five years, so it was exciting to be present at his first plenary lecture at the 12th International Seagrass Biology Workshop in Wales last October. The topic of the plenary, seagrass carbon storage, centred on how seagrasses and their mud, or ‘blue carbon’, are important for dealing with our global climate change problem. Yes, we do work with mud, and blue carbon research has turned out to be quite a dirty and smelly job. I personally did not expect to enjoy playing in the mud well beyond my childhood (while getting paid for it!). But in his plenary, Macreadie laid out how much more there is to the story of blue carbon…

Macreadie began his talk with the facts about blue carbon biosequestration – a long word to describe how plants remove the atmospheric carbon dioxide (CO2) into their tissues or into their sediments. Terrestrial habitats are the most well-known ecosystems that biosequester carbon, but we are finding trees cannot take care of all the CO2 we have produced. A decade ago, clever scientists noticed that coastal or ‘blue’ carbon ecosystems can also biosequester carbon at a rate ~40 times higher than their ‘green’ carbon counterparts. These blue carbon habitats, including seagrasses, mangroves and tidal marshes, can also retain this carbon for hundreds to thousands of years without reaching full capacity. Seagrasses, in particular, not only have the power to help mitigate climate change, but their ecosystems are incredibly important for supporting half of the world’s fisheries and stabilising the coast against erosion.

Macreadie went on to describe the main questions in blue carbon research: 1) ‘Where is the blue carbon and how much is there?’ 2) ‘How do blue carbon stocks change under different conditions like habitat loss, sea level rise and increased temperatures?’ and 3) given that blue carbon ecosystems are a powerful tool against climate change, ‘How can blue carbon be incorporated into global carbon off-set initiatives?’

He highlighted a few areas of seagrass blue C research ranging from carbon loss after disturbance to microbes as the drivers of the carbon cycle to how to optimise carbon biosequestration through management. As a self-proclaimed ‘lab rat’ (with the occasional day out in the water), I enjoy researching these detailed dynamics of blue carbon science. And it is these nitty-gritty questions around seagrass biosequestration that we have answered over the last decade that are paving the way for blue carbon to shine on a cross-disciplinary, international platform.

Specifically, seagrass (and other blue C) habitats are gaining recognition for their monetary value. Valuating seagrasses helps translate their ecosystems services to policymakers, management agencies, and industry. While there are some that consider this valuation process to be a form of profiting off of nature, this new frontier is a priority for many blue carbon scientists, including Macreadie and his colleagues, because of the opportunity to see emphasis put on conserving these ecosystems we love and an opportunity for new funding to be put towards blue carbon restoration research. Many government bodies are coming out in support of both green and blue carbon biosequestration for its role in climate change mitigation, providing a great opportunity for blue carbon experts to be involved in blue carbon off-setting development.

At the end of the plenary, Macreadie circled back to answer the open question: Is seagrass blue carbon just mud? He answered with a yes with the hope that others can see the importance of this mud as a way to both mitigate climate change as well as an innovative pathway for seagrass restoration. As it turns out, we are never too old to play in the mud!