Carbon Sinks Explained: How Storing Carbon Fights the Climate Crisis

Science & Tech
July 2, 2021
Avely Pütsep

Carbon is all around us. And so are carbon sinks. But how do carbon sinks play a crucial role in climate change?

What will you learn about carbon sinks?

  • First things first: what is a carbon sink?
  • Why are carbon sinks important and how do they work?
  • How is climate change affecting carbon sinks?
  • Carbon sink examples
  • Are carbon sinks good or bad?
  • Do carbon sinks turn into carbon sources?

Let’s dig in!

What is a carbon sink?

Carbon sink is any reservoir, natural or not, that accumulates and stores carbon compounds for indefinite periods of time, lowering the concentration of CO2 in the atmosphere.

Too complicated? Let’s unpack it.

Because Earth is a closed system, the amount of carbon never changes. The carbon cycle keeps carbon moving from one reservoir to another.

When carbon stays in a place where the absorption of carbon is bigger than the amount of carbon it releases -> there you have it, a carbon sink!

So a carbon sink is a place that absorbs more carbon than it releases.

A carbon sink acts like a sponge, soaking up carbon compounds like carbon dioxide.

Carbon sinks are crucial in keeping the levels of CO2 in the atmosphere at manageable levels.

Why are carbon sinks important?

Carbon sinks are crucial in keeping the levels of CO2 in the atmosphere at manageable levels.

What happens when we don’t get carbon levels under control? Read the Worst-Case Scenario of Life in 2050, which is actually a very likely scenario if we don’t get our act together.

The short answer to why do we need carbon sinks is really easy: to keep humankind alive! ‍

Are carbon sinks good or bad? There’s no single answer, but since carbon sinks play a huge role in storing excessive carbon that would otherwise heat our planet... Well, then they’re doing pretty good!

Why is it important to mitigate carbon sources into carbon sinks? The CO2 stored in natural carbon sinks such as forests is released into the atmosphere through forest fires, changes in land use, or logging. That’s why it’s essential to reduce carbon emissions in order to achieve climate neutrality.

How do carbon sinks become carbon sources? There are many examples of how carbon sinks become carbon sources. We covered a lot of them in The Carbon Cycle Explained blog post.

How does a carbon sink work?

Carbon sink works through a process called carbon sequestration.

What is carbon sequestration?

Simply put: carbon sequestration means capturing carbon and storing it.

There are many different ways to sequester carbon. We wrote about some of them in Carbon Sequestration Explained.

If the permafrost in Antarctica melts, massive amounts of trapped carbon dioxide gets released into the atmosphere.

How is climate change affecting the carbon sinks?

Carbon sinks are mostly affected by climate fluctuations and seasons.

The performance of carbon sinks varies depending on how warm it is. And we all know about global warming, so that’s not good, right? Right.

Usually when it’s warmer, plants and trees absorb more CO2. When it’s colder, they absorb less CO2, causing the atmospheric CO2 levels to rise.

But – there’s often a “but”. The Pacific Ocean is greatly affected by El Nino and La Nina cycles changing sea surface temperatures. This causes many regions to experience warmer and drier weather and in tropical rainforests it reduces the natural growth of plants. As a result, vegetation’s ability to absorb CO2 is limited. Alarming to say the least.

Some more alarming facts on the connection of the climate crisis and carbon sinks:

If the permafrost in Antarctica melts, massive amounts of trapped carbon dioxide is released into the atmosphere.

Damaged peatlands are a major source of greenhouse gas emissions. It’s crucial to protect the peatlands we have left to keep the carbon that’s been stored there over hundreds of years.

To date, no artificial carbon sinks are able to remove carbon from the atmosphere on the necessary scale to fight global warming. It’s crucial to reduce the amount of carbon we emit.

To date, no artificial carbon sinks are able to remove carbon from the atmosphere on the necessary scale to fight global warming.

What are the main carbon sinks?

The main carbon sinks are forests, oceans, and soil.

What naturally absorbs CO2? The simple answer is: really most of the things on Earth absorb carbon in some way, even if it's for a short period of time.

Where is most of the carbon on Earth stored?

Ocean and land carbon sinks absorb around half of carbon emissions.  

Ocean carbon sinks

What is the largest carbon sink? Is the ocean the biggest carbon sink?

Yes, the largest carbon sink on Earth is the ocean.

Oceans are thought to absorb as much as 25% of CO2 emissions. According to a new study, this number could be even higher.

Why do oceans absorb so much carbon? As the atmospheric concentration of carbon increases, more carbon is dissolved into water. From there, some of the carbon sinks deeper and deeper. If it reaches the deep sea, it’s locked there for hundreds of years(!).

Trees act as carbon sinks through photosynthesis- carbon is absorbed from the atmosphere and deposited in forests.

Forests and plants: amazing CO2 sinks

Are forests carbon sinks? Yes, in fact forests are one of the largest carbon sinks!

How do trees act as carbon sinks?

Simply put: carbon is absorbed from the atmosphere through photosynthesis and it’s deposited in forests.

Carbon is stored in forests in:

  • biomass like roots, leaves, branches, and trunks
  • soil
  • dead organic matter like dead wood

How do plants on Earth affect the amount of carbon in Earth’s atmosphere?

Plants affect it in helping decrease the amount of carbon in the atmosphere.

Why are trees important carbon sinks? Every year forests absorb two times as much carbon as they emit.

Carbon sink: soil

Soil is capable of storing a lot of carbon.

In some ways soil is a lot more powerful than living things in storing carbon:

A study found that 80% of carbon in terrestrial ecosystems is in soil.

Go on, soil.

Earth has lost over 50% of its wetlands.

Wetlands are powerful carbon sinks

Wetlands absorb huge amounts of carbon because it’s harder for plants to decay in these conditions. Therefore the carbon in plants stays put in the plant and the plant stays put in the wetland. Win-win.

Does peat absorb carbon?

It sure does! Peatlands store A LOT of carbon.

Peatlands are the largest terrestrial carbon store. The area covered by natural peatlands all over the world stores 0.37 gigatonnes of CO2, which is more than all other vegetation types in the world, combined!

To make that fact even more impressive, peatlands are just 50% of Earth’s wetlands. Let that (carbon) sink in!

Why are peatlands among the most valuable ecosystems?


  • Are a crucial part in halting the climate crisis
  • Provide safe drinking water
  • Are critical for preserving biodiversity
  • Minimize flood risk

It’s becoming increasingly obvious how important it is to protect the wetlands we have left. After all, Earth has lost over 50% of wetlands already.

It’s crucial to protect intact ecosystems we have left: forest, wetlands, and other natural resources.

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