Mowing down seagrass meadows will cut loose carbon
You wade in the sea around the island? You know, then. It’s everywhere. Drumbeg, Whalebone, Sandwell… on and on. It brushes your legs as you walk about in the shallows, and waves about in the water as the tide comes in. It’s eel-grass, or sea-grass. And here’s an article on its importance from New Scientist: Mowing down seagrass meadows will cut loose carbon.
They may be trickier than trees for environmental protesters to chain themselves to, but it turns out that seagrass ecosystems hold as much carbon per hectare as the world’s forests – and are now among its most threatened ecosystems.
In the past century, 29 per cent of seagrass has been destroyed globally, mostly by water pollution, dredging for new developments, and climate change. With seagrass meadows disappearing at an annual rate of about 1.5 per cent, 299 million tonnes of carbon are also released back into the environment each year, according to research published this week in Nature Geoscience (DOI: 10.1038/ngeo1477).
Piecing together old and new data from 946 seagrass meadows around the world, an international team of researchers estimated that seagrass captures 27.4 million tonnes of carbon each year, burying it in the soil below. And unlike forests that hold carbon for about 60 years then release it again, seagrass ecosystems have been capturing and storing carbon since the last ice age. [continue]
Filed in environment,Gabriola Island 14 Comments so far
14 Responses to “Mowing down seagrass meadows will cut loose carbon”
judith on 21 May 2012 at 11:07 pm #
Yes, sea grass, eel grass, how wonderful as a concept. However, wading about Drubeg, Whalebone and Sandwell up to the present, and over the past ten years, I have not experienced that ‘brushing about your legs’ sensation.
elen on 22 May 2012 at 12:32 pm #
A good site for more information on eelgrass: http://www.stewardshipcentre.bc.ca/static/eelgrass/eelgrassachievements.html
elen on 22 May 2012 at 12:41 pm #
and http://www.birdsonthebay.ca/eelgrass.html
Westcoast995 on 23 May 2012 at 7:35 pm #
Someone seems to be using some snake oil science here. All plants and vegitation require carbon dioxide to live. In return they process it and release oxygen that enables all animal life to live. Eliminate carbon dioxide from the atmosphere and all vegitable life and animal life will die off.
It is true that different vegitation processes carbon dioxide at different rates, but it is part of the natural cycle of life on earth. Modern man should not try to change nature – that is only a slow endgame for life on earth.
Gabriolan on 23 May 2012 at 8:57 pm #
Thanks for the links, elen. Sorry for the delay in publishing one of your comments here – it got caught in the spam filter.
Anon E Mouse on 24 May 2012 at 6:56 am #
Westcoast995, I’m with you on that comment about changing nature can be a slow endgame for life on earth. In my opinion, the human species has been far too reckless in that respect.
But for the rest of it, I don’t think it’s snake oil – I think the important point is that eelgrass (and tropical seagrasses – eelgrass is the only temperate zone one) beds do trap carbon and bury it, which at this stage in our planet’s history is a Very Good Thing. Yes, we need carbon dioxide in the environment for plants to live, but we don’t need nearly as much as what is now being released by human recklessness. When eelgrass metabolizes, some of the carbon it takes in is shunted down to the roots and rhizomes as stored energy. Some of that carbon ends up in leaves, but when they die off some of them fall down and are trapped among the eelgrass blades where they decompose and add to the carbon in the sediment under the eelgrass bed. Because there is a constant rain of organic matter of this kind, and also the presence of the eelgrass ‘forest’ tends to trap organic material floating about (the speed of the current drops as it flows through the bed), a lot of organic carbon gets trapped under the eelgrass. While the eelgrass bed is alive, the roots and rhizomes stabilize the sediment underneath so the carbon stays put. If the eelgrass dies, the roots and rhizomes disintegrate so the sediment is no longer stabilized, the aboveground structure of the plant is gone, so the currents flow faster, and the fine organic sediments that were under the eelgrass get washed away by currents so the area that used to be an eelgrass bed might return to mostly inorganic sand with very little carbon still present. All the carbon that was held in that fine sediment is now suspended in the water column and available to be released into the environment, atmosphere, etc. The point I take away from the article is that seagrasses sequester an awful lot of carbon and that the sudden release of carbon added into the atmosphere on top of what we are already releasing, which could conceivably occur if all the seagrasses were to be killed off, would be a Bad Thing. Think of seagrasses as contributing to our safety net. And so we need to protect what’s left of our seagrasses and try to promote their recovery.
Carbon-trapping is only one of the important things eelgrass does in the marine coastal environment. I’ll save the rant about the other things for another day ;)
Sheila M on 24 May 2012 at 2:18 pm #
This is a fascinating topic. Here are some links:
http://www.sierraclub.bc.ca/media-centre/press-clips/local-estuaries-key-to-climate-health
http://www.sierraclub.bc.ca/media-centre/press-releases/protect-estuaries-for-effective-sea-burial-of-carbon-says-sierra-club-bc (the link to the actual report is broken)
http://www.sierraclub.bc.ca/blog/blue-carbon-2013-good-news-from-the-ocean
I heard there was a MA student at UVic working on measuring the carbon sequestration value of eelgrass, and the potential for developing carbon credits from planting eelgrass. I think the work involved Snuneymuxw and the Nanaimo Estuary.
I also heard there is some good work being done by Project Watershed up on the Courtenay River Estuary.
Gabriolan on 25 May 2012 at 10:57 am #
Thanks, Sheila! I’ll have lots to read today. :-)
elen on 25 May 2012 at 5:01 pm #
In case you want even more to read … look what these school kids “just up the road” have been working on for the past few years!
http://www.mvihes.bc.ca/educate/programs/eelgrass-mapping
Gabriolan on 25 May 2012 at 9:20 pm #
Thanks, elen. That is very cool!
Joan on 26 May 2012 at 1:16 am #
Well, Gabriolan, do not forget that you illustrated the eelgrass part of a report (note the photo credit) : you have to add this to your reading list.
I wrote this overview, and when I was doing the research for it, I was quite surprised at how difficult it was to find information in Canada about eelgrass meadows – not much is known about declines, which are quite serious on the east coast and in James Bay.
Link to section on eelgrass in assessment report on Canada’s ecosystems
Gabriolan on 26 May 2012 at 10:06 pm #
Joan – Thanks for reminding me about that report, which is excellent and informative. Thanks also for the photo credit. :-)
eljay on 31 May 2012 at 7:37 am #
Hi fans of seagrass
Have you heard the Kerplunks Eelgrass song? It is on their CD called ‘Walk On’.
There is a working group of eelgrass mappers on Gabriola. Half of the island coastal waters have been surveyed and mapped so far over the last few years. The group meets informally to chew on bite size pieces of the mapping puzzle. Mapping is an important first step in monitoring the state of eelgrass in our neighbourhood.
Mapping is done based on the protocol set out by Seachange. http://www.stewardshipcentre.bc.ca/static/eelgrass/index.html.
If you are interested, the group is in need of volunteers and enthusiasm to continue this important work. Volunteers may contact Laura Jean Kelly.
Gabriolan on 06 Jun 2012 at 7:58 pm #
Wow. Thanks, eljay.