Carbon sink
September 9, 2025What is a carbon sink?
A carbon sink is any system that absorbs more carbon than it releases into the atmosphere.
Carbon sinks vs. carbon sources
Carbon sinks are the opposite of carbon sources, which produce more greenhouse gas (GHG) emissions than they absorb from the air.
Trees, forests, oceans, and soils act as carbon sinks, whereas deforestation or burning fossil fuels like oil, coal, or gas creates carbon sources.
Carbon sink examples
There are two kinds of carbon sinks: natural and artificial. Both operate on the same principle of reducing the concentration of carbon in the atmosphere, but through different processes.
Natural carbon sinks like the ocean and forests
The ocean: Often called “the lungs of the planet”, the ocean is the largest carbon sink, absorbing about 30 percent of all human-generated emissions. This happens through two main processes:
The physical carbon pump: Carbon dioxide dissolves in the ocean’s surface waters and is transported by currents into the deep sea, where it can remain stored for centuries.
The biological carbon pump: Microscopic marine plants called phytoplankton absorb carbon and, through photosynthesis, convert it into organic material. When these organisms die, their remains sink to the ocean floor, storing carbon for the long term.
Land: Forests, wetlands, peatlands, grasslands, and soils all function as carbon sinks. Trees and plants absorb carbon dioxide through photosynthesis, storing it as organic matter in trunks, branches, roots, and leaves. When this material falls to the ground, it enriches the soil with carbon, where it can stay sequestered for decades or even centuries.
Artificial carbon sinks
Carbon capture and storage (CCS): This technology reduces carbon emissions by capturing greenhouse gases from industrial processes or power plants before they reach the atmosphere. The captured gas is then stored deep underground for centuries or even millennia.
Why are carbon sinks important?
Carbon is essential to life on earth and is everywhere, from carbon dioxide in the air to organic matter in living organisms, as well as in fossil fuels and limestone.
Carbon sinks and sources are a part of the delicate carbon cycle, which describes how carbon moves between the atmosphere, ocean, soil, plants, animals, and rocks. This cycle regulates the amount of carbon in the atmosphere, which in turn influences the planet’s temperature.
Because carbon dioxide is one of the main greenhouse gases responsible for climate change, carbon sinks help reduce its concentration in the atmosphere.
However, human activities such as deforestation and burning fossil fuels disrupt this balance by increasing carbon emissions while diminishing the capacity of carbon sinks to absorb them. With the carbon cycle out of sync, extreme climate events like heatwaves, floods, and droughts are becoming more frequent.
How can we protect carbon sinks?
To reduce carbon levels, we must not only protect existing sinks but also create new ones. This includes safeguarding coastal ecosystems like wetlands and marshes, preventing deforestation, and establishing resilient forest ecosystems.
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