By M. Creurer
Oysters have long been regarded as “canaries of the sea,” providing an early warning for contaminated waters along our shores. Recent studies from Australia now show that this humble mollusk, the mighty oyster, also plays an important role in combating global warming.
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Climate changes induced by global warming have become a heavily discussed topic over the last two decades. According to some, the worsening situation may even pose a threat to the very existence of mankind. This has given rise to a world-wide quest for ways to help combat the cause and effect of global warming.
Carbon emissions spewing from cars, airplanes, factories, outboards, etc. are creating greenhouse gases in the atmosphere which causes global warming. In order to combat global warning, we must first reduce the amount of carbons being released… but, we must also remove the emitted carbon from our environment. This latter process has become known as bio-sequestration.
It has long been accepted that trees reduce the effects of greenhouse gases. They absorb carbon from the air, and through the process of photosynthesis convert carbon dioxide into oxygen. The more trees on a hectare of land, the greater the amount of carbon being converted into oxygen.
Our oceans, with their large surface areas, also act as “carbon sinks,” drawing carbon from the air. This exchange between the terrestrial biosphere and the ocean absorbs almost 50 per cent of anthropogenic emissions. But, the carbon carrying capacity of our waters is limited.
“As the global average temperature increases and CO2 within the ocean begins to reach saturation the ability of the ocean to absorb carbon will alter significantly,” writes J. P. Hickey, School of Natural and Built Environs, University of South Australia.
“At some point in the future,” he goes on to say, “removing carbon from the ocean may need to be considered. One method for achieving the removal of carbon from the ocean would be through the ancient practice of shellfish farming.”
As the shellfish forms and grows, it absorbs carbon naturally from the water by secreting calcium carbonate (CaCO3) to form its shell. A significant percentage of its shell contains carbon – 12g for every 100g of shell, or 12% of overall shell mass. The Pacific oyster, Crassostrea gigas, is seen as having the greatest potential for absorbing carbon from water.
Case studies show that a typical oyster farm sequesters a large amount of carbon over the years – more than 4000 kg per hectare – surpassing some types of trees. The main advantage of oyster farming is that unlike other ocean sequestration techniques, the oyster shell permanently removes carbon from the ocean. This aspect will become more important as global warming and ocean carbon capacity affect the amount of carbon absorbed by oceans.
The oyster industry is well established, and recognizing shellfish as a carbon sink under the Kyoto protocol could be of great benefit to us all, particularly to regional areas.
Save our planet – plant a tree – seed an oyster!