Seagrass prairies, ecosystems that must be preserved as much as coral reefs

Seagrass prairies form in seawater along the coastlines of every continent, except the Antarctic. They are composed of more than 70 species of aquatic plants. Although their surface area occupies only 0.15% of sea beds, their ecological importance is considerable: their stabilisation of sea beds is necessary for the good state of coral reefs and the combat against coastal erosion; they produce organic matter and are a source of food; they provide spawning grounds and shelter for numerous organisms; and they capture carbon. Their capacity to produce organic matter and oxygen is comparable to that of tropical forests, coral reefs and mangroves.

High carbon stock

They may be even more precious in the carbon cycle than previously thought. According to a new study published in Biology Letters, it is now estimated that 7 billion tonnes of carbon have been captured and stored in the soil by seagrass roots over thousands of years, carbon that would otherwise have contributed to climate warming in the form of carbon dioxide.

However, this “blue carbon”, the name given by scientists to these seagrass prairies and mangroves, is very sensitive to disturbances to its environment, caused by pollution, navigation and rising water temperatures.

It is estimated that these marine prairies are disappearing at a rate of 1.5% a year worldwide, a decline comparable to that of tropical forests, mangroves and coral reefs. If they are not better protected, especially from the effects of climate change, their capacity to mitigate it will weaken: an obvious cause and effect relationship!