What exactly is a carbon sink, and why you should care about them more

Monday, September 7, 2020

Saving the climate requires growing and maintaining carbon sinks. But if it’s been a moment since you last sat in an environmental studies class, you might not be entirely sure what exactly a carbon sink is. 

So, what is a carbon sink?

A carbon sink is basically anything that biologically or physiologically holds more carbon in than it releases. This way, a carbon sink keeps carbon from entering the atmosphere as CO2. It can be something natural, like a tree, or something completely artificial.

Why exactly do carbon sinks matter?

Two of the most important carbon sinks on the planet are oceans and vegetation, ie. plants and trees. Carbon is a very common element, and it naturally moves in and out of these sinks by everyday processes: Trees and plants absorb CO2 in photosynthesis and use it to grow and to produce oxygen. Animals – and you and me – take carbon in in the form of carbohydrates and breathe out CO2. 

In this natural cycle carbon moves between processes all over the planet: When just the right amounts are stored and released at the same time, everything’s quite nice. The problems start when you and I shake that balance and release way more than is stored.

Oil and coal are carbon sinks too – and that’s the problem.

As a tree grows, it stores carbon in its roots, leaves, branches and trunks. Plant litter also stores carbon into the soil. When the plant litter and fallen leaves decompose, carbon is released back into air. And if we cut the tree down and burn the wood, carbon is again released into the air. What’s more, there’s no more tree to keep on storing more carbon.

Here’s why fossil fuels are such a problem. 

Coal, oil and natural gas are all carbon sinks too. Mama Earth has stored massive amounts of carbon into these materials through millenia. Now, as humans use these resources, the carbon is being released into the atmosphere quicker than new sinks are being built. When we burn fossil fuels, carbon goes back into the atmosphere. When we transform limestone into cement, carbon goes back into the atmosphere.

If you think of a sink, its main purpose is to hold water until the water is drained out. While nature lets out just the amount necessary at any given time, we’ve been pulling plugs and spilling all over.

And there’s more! Caring for carbon sinks actually matters more now than ever before.

Once we understand that nature has the ability to store carbon, we must also understand that this magic only happens under certain conditions. 

That’s why a crucial part of truly understanding the urgency of climate action is to understand how some of the current carbon sinks might stop absorbing carbon in the future. 

They might stop absorbing, and what’s worse is they might actually start releasing carbon too. Currently, oceans store carbon. But if salt water temperatures rise, oceans might change how much CO2 they absorb. If the frozen tundra warms up, it can start producing greenhouse gases, which it’s too cold to do now. There's been studies that if global temperatures rise, tropical forests might turn into carbon leaks too.

If we lose these natural carbon sinks, it would require us to grow impossible amounts of artificial sinks to actually still keep the globe from warming.

So, if we want to save the climate, we must cut emissions and save the carbon sinks.

It’s not all doom and gloom. We know all this because hundreds and hundreds of scientists have dedicated their lives to studying the climate and the planet. We also know that carbon sinks can be restored, maintained and grown! Offsetting is one way to do that. We can form forests, plant new trees, and preserve existing, old forests, like many of the projects in Compensate’s project portfolio . We can and should implement overcompensation where ever possible, so that we always remove more carbon than we initially created through consumption.

And natural processes aren’t the only carbon sinks! Artificial methods are being developed and studied as we speak. Some of these examples include things like mechanically capturing CO2 from air, storing CO2 deep underground, and harvesting CO2 as material for a variety of products (like vodka, we kid you not). At Compensate, our way of contributing is dedicating 20% of our portfolio to these newer, innovative methods.


Compensate is here to enable easy access to the highest-quality carbon capture – for businesses and for individuals. Together, we can make a difference.

Sources and further reading for the curious minds:

NASA Science: Carbon Cycle

Permafrost Becoming a Carbon Source Instead of a Sink

Sinks and Sources – Awesome Mangroves

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