You might have often heard how our forests and the oceans help in reduction of greenhouse gases. Ever wondered how? Well they act as carbon sinks and trap the excess carbon dioxide from the atmosphere. With climate disasters becoming more frequent and alarming, the role of carbon sinks become more significant. Carbon sinks on land are estimated to soak up a quarter of the world’s emissions, a powerful tool to combat global warming. Natural carbon sinks, such as forests, marshland and the ocean, are an important mitigating tool in the fight against climate change because they trap more carbon than they release into the atmosphere.
Carbon sinks are natural or artificial systems that absorb and store carbon dioxide (CO2) from the atmosphere, helping to mitigate the impacts of greenhouse gas emissions on climate change. Carbon sinks act as reservoirs that remove carbon dioxide from the atmosphere and store it for long periods.In fact, any place or product that absorbs more carbon than it emits into the atmosphere can be considered a carbon sink.
Besides forests and oceans, some of the natural carbon sinks include wetlands (marshes, swamps, and peatlands) which accumulate carbon in their vegetation. Similarly, soil can store substantial amounts of carbon and practices like carbon farming, agroforestry, and conservation agriculture enhance carbon sequestration in soils. Another significant natural carbon sink is mangroves that absorb and store carbon in their roots, trunks, and sediment. Phytoplankton and other marine organisms also contribute to carbon sequestration in the oceans.
Carbon sequestration is the process of capturing and storing CO2 from the atmosphere, removing it from the carbon cycle and preventing it from contributing to the greenhouse effect and climate change. Blue carbon refers to the carbon stored in coastal and marine ecosystems like mangroves, seagrasses, and saltmarshes. Under artificial carbon sequestration, CO2 is captured at the source, such as power plants or industrial facilities, and stored underground in geological formations such as carbon capture and storage (CCS).
Essentially, a carbon sink is the reservoir or system that naturally or artificially absorbs carbon, while carbon sequestration refers to the process of capturing and storing that carbon to prevent it from contributing to climate change.
Carbon sinks work by absorbing and storing carbon dioxide (CO2) from the atmosphere, thus reducing its concentration and mitigating climate change. The carbon captured by plants during photosynthesis is stored in their biomass, including trunks, branches, leaves, and roots. This carbon remains locked within the plant’s structure, temporarily removing it from the atmosphere.
When plants shed leaves, branches, or die, organic matter containing carbon accumulates on the forest floor or within wetland sediment. This organic matter can undergo decomposition, but in oxygen-depleted conditions, such as in wetlands, the carbon can be preserved and stored in the soil for long periods.
Oceans act as carbon sinks when surface waters of the ocean exchange CO2 with the atmosphere and the dissolved carbon is transported to deeper layers through mixing and ocean currents. Marine organisms like phytoplankton also absorb CO2 through photosynthesis, with some of the carbon sinking to the ocean depths when the organisms die and sink.
The capacity of carbon sinks to absorb and store carbon is influenced by various factors, including the health of ecosystems, land use changes, climate conditions, and human activities. Forests, for example, can store carbon for decades to centuries, while carbon stored in soil and deep ocean layers can remain sequestered for even longer timeframes.
According to a recent report published in The Washington Post, a pileup of ancient logs nearly as big as Manhattan is trapping millions of tons of carbon in northern Canada — and much of that stored material could be released into the atmosphere due to climate change. So protecting existing carbon sinks and restoring degraded ecosystems are critical for maintaining their carbon sequestration potential and mitigating climate change.
During the pre-industrial era, whatever carbon was produced was evenly balanced using carbon sinks. But today, out of all the excess carbon dioxide that we are producing, only half of it is absorbed by natural carbon sinks. The remainder of this excess carbon is trapped in the Earth’s atmosphere and is the driving force behind global warming. The excess carbon traps the heat which warms the planet and drives climate change.
So carbon sinks are crucial as they help in mitigating climate change by absorbing and storing CO2. Carbon sinks also play a vital role in balancing the carbon cycle, which is the natural exchange and flow of carbon between the atmosphere, oceans, land, and living organisms. They act as reservoirs that prevent excessive buildup of CO2 in the air and maintain a natural equilibrium in the carbon cycle. Many carbon sinks such as coral reefs, are also biodiversity hotspots helping protect endangered species and sustain ecosystems. Coastal ecosystems like mangroves and saltmarshes act as carbon sinks and also serve as natural buffers against storm surges and coastal erosion. Carbon sinks, such as forests and soils, also contribute to sustainable resource management by providing timber, non-timber forest products, clean water, soil fertility, and other ecosystem services. Preserving and restoring these ecosystems can enhance resilience to climate change impacts.
Many carbon sinks such as coral reefs, are also biodiversity hotspots helping protect endangered species and sustain ecosystems.
The importance of carbon sinks have been recognised by several countries that often include carbon sink protection, restoration, and enhancement as part of their climate action plans.
For instance, according to government figures released by India in 2022, the carbon sink in the country has increased by 703 million tonnes of CO2 equivalent in the six years since 2015 or roughly by 120 million tonnes every year. India has committed to increase its carbon sink by 2.5 to 3 billion tonnes of carbon dioxide equivalent by 2030 through the creation of additional forest and tree cover. Carbon sinks also play a significant role in international climate agreements and strategies to address climate change, such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement.