Natural Carbon Sequestration in Our Coastal Waters

Scientific explanations of climate change facts can be confusing for us all. I decided to do some reading to see if I could wrap my brain around some of the facts, and I discovered that I had a lot to learn! I was particularly interested in finding out more about coastal habitats such as seagrass beds and saltmarshes sequestering carbon. This sounds important and amazing - but I did not have a clue what it meant! So after some digging, I discovered just how natural carbon sequestration in coastal habitats works. Here is what I discovered.


Carbon Cycle
It all starts with the carbon cycle, which is the movement of carbon atoms through all things on the planet: the atmosphere, living and non-living organic material, our bodies, oceans, sediments (including fossil fuels) and the Earth’s core. There is a balance between these major reservoirs of carbon. Some things, like volcanic eruptions and burning fossil fuels, increase the amount of carbon in circulation in the atmosphere and oceans. Other natural processes like photosynthesis remove and store it. Plants take carbon from the atmosphere in the form of carbon dioxide, and through photosynthesis turn it into the sugars and carbohydrates that form plant material. Some of this carbon in plants is consumed by other animals that use the carbon to build their own bodies. Some carbon returns to the atmosphere and oceans or into soil or marine sediments as life forms decompose. Although the carbon cycle is on the move, the proportion of carbon that is in our oceans or atmosphere has been pretty steady over the years, allowing the species that depend upon it to evolve based on its presence in set concentrations.




Sequestration of Carbon
The carbon cycle makes it seem as though carbon is always on the move, but much of our planet's carbon has been stored for millions of years, in fossil fuels, and for hundreds of years in large trees. So you can see why cutting down trees and burning fossil fuels has upset the carbon balance: It is all back in in the atmosphere and oceans! What is needed, in addition to to halting the burning of fossil fuels, are actions like protecting and increasing forest cover and supporting other processes that take carbon out of circulation from the air and water then store in a stable solid form. There are many schemes to artificially sequester carbon, but most of them are so energy intensive that they would create as much of a carbon footprint as they elevate, some would take to long to be useful on a massive scale, and others have been banned from consideration due to unknown side effects that could be worse than the problems we are starting with!

Natural Carbon Sequestration
Natural carbon sequestration is carbon stored by plants and animals. The most effective form is when terrestrial and marine plants sequester carbon into the soil or sediments around their roots in a mineral form, storing it for thousands of years or more. These carbon sequestering plants are extremely important for reducing the amount of carbon circulating in the atmosphere and oceans. Of these, the marine coastal habitats such as mangroves, salt marsh and sea grass do this job the best. Marine species sequester the same overall amount of carbon as terrestrial species, even though there is 99.95% less plant material in the oceans doing the same job. This is due to special chemical processes in marine sediments. (This means half a kilogram of marine plant material can sequester as much carbon as 1,000 kgs of plant material on land)

Protecting Seagrass and Saltmarsh
Seventy percent of the marine plants that naturally sequester carbon are found in coastal areas such as seagrass meadows and salt marshes. Much of these areas have been lost since the 1940s due to coastal development, and have been damaged by run off from agricultural and industrial activities. Scientists of the United Nations Environment Program recommended to the 2009 Copenhagen Climate Change Conference that 80 percent of the world’s remaining seagrass and salt marsh habitat be protected as an important step among the range of strategies necessary to combat global climate change and ocean acidification.

So given that we know what to do - why aren't we doing it?

There is one thing you can do right now that would only take one minute. Send a letter to our Minister of Fisheries and Oceans - telling her about the importance of protecting these critical habitats with marine protected areas in order to ensure that they keep on sequestering carbon.



Information about natural carbon sequestration (if you want more) is also available in these reports.

* IUCN: The Management of Natural Coastal Carbon Sinks
* UNEP: Blue Carbon Report