Oceans 2050 has revisited and doubled previous estimates after assessing the size of algal forests around the world.
Seaweed covered an area of about 3.5 million square kilometers of the coast, according to the original 2016 study by Krause-Jensen and Duarte.
Hence, it estimated 1.52 petagram of net productivity of carbon annually, amounting to 640 million tons of sequestered carbon.
New data shows these algal forests globally to be double in size, covering an area of 7.2 million square kilometers, as estimated by Professor Duarte.
This represents potential productivity of 1.3 petagrams of carbon annually, mirroring the productivity and size of the Amazon rainforest.
Oceans 2050 measured the CO2 contents in sediment cores below 21 seaweed farms from 5 different continents and found the average rate of carbon sequestration to be 1.4 tons of CO2 annually per hectare.
However, there was a huge difference between farms, ranging from 0 to 8 tons of CO2.
A higher concentration of carbon was found in the places near soft sediment or low wave energy. However, there was no carbon accumulation on seaweed farms located over rough sand, rocks, or sites with strong currents.
Gallagher et al. researched the kelp forest’s potential to sequester carbon, which proved to be a breakthrough observation in the seaweed community. They found out that kelp forests are more of a carbon emitter than a carbon sink.
Professor Duarte immediately rejected the paper’s conclusions as the data set of the paper was incomplete. The team is now refining the work done by Gallagher et al. to rectify the mistakes and justify the claims.
Both Duarte and Gallagher want to closely observe what an ecosystem is replaced with when it disappears and how this replacement will contribute to greenhouse gas emissions, nutrient cycle, and biodiversity.
An urchin barren is usually a replacement in the case of kelp forests, offering almost no benefit to the ecosystem.
Verification of carbon removal
Oceans 2050 has already submitted a concept note with Verra to have the carbon sequestration properties of farmed seaweed officially verified.
This is a necessary first step to kickstart the approval process for carbon credits, although it will likely not be an easy procedure, as currently, there is no reliable Monitoring Reporting Verification (MRV) technique to measure the carbon removal of seaweed.
A more detailed explanation of the process, as well as detailed coverage of developments in the seaweed industry can be found at Phyconomy.
Read more: Phyconomy: Seaweed Industry Is On The Rise