by Giulia Granato and Mauro Doimi, Marine biologists, D&D Consulting, Italy

Most of human activities emit carbon dioxide (CO2), which contains atmospheric carbon.

CO2, along with other emissions, have changed and is still changing global climate irremediably. What is not still well known is that our ocean, coasts and lagoons provide a natural way of reducing the impact of greenhouse gases on our atmosphere, through sequestration (or sinking) of this carbon.

83 percent of the global carbon cycle is circulated through the ocean. Coastal habitats cover less than two percent of the total ocean area, but account for approximately 50 percent of the total carbon sequestered in ocean sediments. The term used for carbon captured by marine ecosystems is called 'Blue carbon'.

Carbon is taken by living organisms that store it in an organic form, like mud sediments or for building clam shells. Mangroves, salt marshes and seagrass 'capture and hold' large quantities of carbon, acting as something called a 'blue carbon sink'.

Fish farming is directly involved in the carbon cycle and can be positive in emissions or negative in the sink. Extensive aquaculture made in wetlands or in brackish lagoons proved to be an efficient blue carbon sink.

These ecosystems, strongly autotrophic, fix carbon dioxide photo-synthetically as organic matter and the excess of the CO2 is respired back by biota, thus removing CO2 from the atmosphere and storing it below the ground. The CO2 cycle is complex and begins from its capture in the water by atmosphere and photosynthesis due to the macro-micro algae.

The CO2 reacts with carbonate alkalinity in the brackish water and precipitates on the bottom. Moreover, the CO2 is captured by the mud due to the denitrification process and the chemical linkage with the cations and clay. It has been shown that the biomass production in brackish lagoons is higher than other blue ecosystems, like lakes or rivers, sequestering carbon at a much faster and bigger rate.

Consequently, aquaculture in brackish lagoons plays a doubly important role: these ecosystems sequester tonnes of blue carbon and produce fish in a sustainable and organic way, whilst ensuring the conservation of the natural habitat. Fish are kept wild and live in perfect balance inside the lagoon food chain.

Extensive aquaculture produces less negative ecological impacts on the environment: to the contrary other methods of fish farming like offshore cages produce organic waste, such as fish sewage, and do not remove it.

Therefore, it is urgent to encourage every sustainable system that can mitigate climate change to protect the habitat which has a low 'carbon footprint'.

Fish farms in lagoons should be incorporated into the carbon market through the method of buying and selling carbon credit international called 'carbon offsets'. A carbon offset is a reduction in emissions of carbon dioxide made in order to compensate for emissions made elsewhere. From Kyoto's protocol to the most recent Climate Change Conferences (COP24 in Katowice), our carbon footprint is highlighted as the main indicator of the evaluation of environmental impact.

There are three certifications for fish production identified worldwide: Friend of the Sea, the Marine Stewardship Council and Organic. These accreditations include references on environmental sustainability but they lack objective measurement methods.

Instead, the new certification 'BNeutral' follows the main climate change guidelines and reveals itself to be the most effective standard of the assessment of actual fish sustainability.

BNeutral is a standard that proves the effective sustainability of fish farms in relation to climate exchange. This calculation is voluntary and it is validated by BIOS s.r.l., an international independent control and certification body based in Italy that operates in the voluntary market of the carbon economy.

There are three possible actions inside the standard:

  • In the first action, the 'Blue Carbon Footprint' (BCF) of every product or process is calculated. The identified BCF must be reduced by the farm following the BNeutral standard, generally using solar and wind energy to do so
  • The second action sees the farm that can neutralise the carbon emissions acquiring carbon credits by the carbon market, and the emissions must be balanced by the credits. The farm obtains a label that proves the Total Carbon Neutrality (Carbon zero) of its processes and products
  • In the third action, the emission sink is traded into 'blue carbon credits' that can be bought from other companies and the money revenue can be used to maintain the farm itself.

Now, fish and mollusc commercial production can be considered sustainable in relation to carbon footprints and companies can get a new product qualification that fit the guidelines of the COP24. BNeutral labelled fish farms can be valorised and their marketing protected by the other fish farm productions.

So, why is it so important to combine aquaculture with the carbon market? First, this approach creates a financial incentive for restoration and conservation projects for our lagoons and marshes that are being lost at a high rate.

Furthermore, carbon footprint credits can help sustainable aquaculture farms to gain profit from improved environmental control in terms of carbon CO2 sink, in addition to neutralising greenhouse gases. If less carbon dioxide is emitted, less pollution is created and it is less taxed, generating a positive effect on the global community.

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