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How Blue is your Carbon?


Nick Crouch

We all know that climate change is a serious problem facing the globe, and that it is caused by carbon pollution in the atmosphere. The planet can absorb some of that pollution if given a chance, thereby mitigating the effects of climate change. What you may not know is that much of the Earth’s capacity to absorb carbon is in mangrove, seagrass and coastal saltmarsh communities.

Blue Carbon, as it’s known, in these ecosystems accounts for 5-11% of global carbon stores, yet these same ecosystems cover an area equivalent to only 0.2% of the ocean surface. Mangrove forests, for instance, can store 5 times more carbon than terrestrial forests and capture it 50 times faster. Conversely, destruction of these habitats can release much of the stored carbon, thereby adding to the pollution load in the atmosphere.

Consequently, understanding how these communities change over time, especially in response to a changing climate and more local impacts, is critical to allowing us to maximise their carbon sequestration capacity.

Which brings us to the Earthwatch project, Protecting the Reef’s Coastal Frontier. It aims to learn how mangrove systems change over time, specifically by comparing Daintree mangrove forests (impacted by climate change) and Mackay mangrove forests (impacted by both climate change and local industry). For instance, how does species composition, density, coastal retreat and the amount of carbon captured change under various threats? How do mangroves and samphire sequester carbon and what will happen to that carbon sequestration as a result of climate change?

The Daintree observations have been recorded continuously since 1986, while the Mackay data is only this year being revisited. Quadrats were first established in Mackay in 2002 to monitor the local dieback of Avicennia marina, Grey Mangrove. This sudden and massive dieback was most likely as a result of herbicide washing off nearby canefields (A. marina absorbs more salt than other mangrove species so is more susceptible to herbicides in salt form). This was a controversial finding, however, and funding to continue the research was lost. But this current project will reestablish those same quadrats and build on the previous data. So there is another, smaller, purpose for this research - to examine how the Mackay mangrove forest has recovered following that earlier catastrophe.

And so begins my week of assisting ecologist, Jock MacKenzie from Mangrove Watch, and the Earthwatch team. It promises to be fun. It promises to be muddy. But most of all, it promises to be valuable research into climate change mitigation.