The oceans play a fundamental role in regulating the Earth’s climatic equilibrium. They absorb heat and redistribute it around the world through marine currents and interactions with the atmosphere. They also absorb some of the gases present in the atmosphere. The increase in the concentration of greenhouse gases in the atmosphere is bringing an increase in the average ocean temperature. Additionally, the absorption of large quantities of CO2 leads to an increase in the acidity of the water. It is estimated that the oceans have become 30% more acidic since the Industrial Revolution.
The consequences of these changes have already been felt, particularly in the deterioration of large zones of coral reef. Scientists believe that this acidification could reduce seawater’s supply of calcium carbonates, particularly aragonite, a very important substance used by many organisms to build their shells.
According to a 2009 UN report, healthy oceans are the most effective and cheapest system for catching and storing carbon in the world. A large part of emissions, for example, is trapped and stored by marine ecosystems such as mangroves, salt marshes and seagrasses. The report says that “a combination of reducing deforestation on land as well as restoring the coverage and health of these marine ecosystems could deliver up to 25% of the emissions reductions needed to avoid ‘dangerous’ climate change.”