The decreasing sea meadows off the coast of Australia led to the issuance of additional 11-21 million tons of carbon dioxide equivalent emissions of five million cars a year. To such conclusion researchers have come, having studied the concentration of soil carbon in one of the bays of Western Australia. As noted in their article for the journal Global Change Biology, although sea meadows is less than two percent of the total surface of the Earth, their role in slowing climate change disproportionately. That is why these ecosystems need to be measures for protection and restoration.
The seas grow not only algae, but also true flowering plants — the so-called sea grass. There are 60 species of sea grasses, belonging to four families: posidoniaceae (Posidoniaceae), wspornikowe (Zosteraceae), Vodorezova (Hydrocharitaceae) and cymodoceaceae (Cymodoceaceae). In shallow waters they sometimes form extensive marine meadows — a rich life of the ecosystem that absorb carbon dioxide is several times faster than forests on land.
Unfortunately, human activities are leading to the extinction of Maritime grasslands around the world. First and foremost, they suffer from contamination of water by fertilizers, development of the coastal areas and heat stress resulting from climate change. According to some estimates, 1990-2000 sea-meadows declined by seven percent per year. Meanwhile, when these ecosystems are dying, they stored carbon is released under the action of soil erosion and increases global warming.
A team of researchers led by Christian Salinas (Cristian Salinas) from Edith Cowan University decided to evaluate how much additional carbon was in the atmosphere due to the loss of sea meadows near the Western coast of Australia. As a model of the water area, they used a Bay of Cockburn Sound, located South of Perth. Here, the area covered by sea-grass, from 1967 to 1999 decreased by approximately 80 percent. The main reason for this process was eutrophication due to development of cities and ports.
The authors selected 13 core samples of soil in areas where marine meadows have disappeared in the second half of the twentieth century, and 24, where they remained until now. The obtained samples were measured the concentration of soil carbon and a range of other parameters.
The analysis confirmed that the loss of buffer from sea grasses has led to soil erosion under the influence of waves. Depending on the depth it went with different speed in shallow water was affected by the layer thickness of 30 centimeters, and at greater depths, the figure was eight inches.
Due to erosion soil loses carbon. In samples taken on the remaining areas of shallow meadows, the concentration of soil carbon was nine times higher than where the grass cover has disappeared (p<0.001). At greater depths, however, the difference was not observed. This means that carbon losses in the result of a loss of sea meadows do not occur everywhere, but only where the power waves big enough for active mixing sand that is in the upper layers of water.
In total in the second half of the XX century the Bay of Cockburn Sound has lost 92 percent of soil carbon in the upper 50 centimeters of the soil. This is equivalent to emissions from 0.06 to 0.14 million tons of carbon dioxide. If we extrapolate the findings to the whole of Australia, the sea-meadows in the shallow waters of this continent has led to additional emissions 11-21 million tons of CO2. This increased national annual emissions by 1.1 to 2.3 percent, which corresponds to the emissions of five million cars. The authors warn that these numbers may be greatly underestimated because the scale of the loss of sea meadows is likely higher, than was considered still.
Marine meadows occupy only one tenth of one percent of the earth’s surface. Nevertheless, the study demonstrates that their disappearance can cause disproportionately large emissions of dangerous climate change carbon dioxide. Thus, the conservation and restoration of seagrass beds should be a priority in the fight against climate change.
In the capture of carbon dioxide from the atmosphere involves not only sea grass, but the more common algae. As proved by researchers from Saudi Arabia, fragments of these plants accumulate at the bottom all over the ocean, bringing significant amounts of carbon from the global cycle. This means that they can play an important role in slowing climate change.
Sergey Knee High