The “CO2 is food for trees” argument

Climate change denial takes many different forms : some people say it’s not happening, some people say it’s completely natural and some people say it’s beneficial. The last argument is gaining popularity, you’ll not find it only in the comment sections on Facebook, but also on the twitter page of the president of the US (1). ”Carbon is the building block of life”, ”trees eat carbon”, ”higher carbon concentrations in the atmosphere will make the planet greener” are a couple of formulations of the same argument, that we’ll try to deconstruct in this article.

Carbon is good

Plants need carbon dioxide in order to perform photosynthesis, without CO2, life on Earth wouldn’t exist as we know it. Carbon is indeed the building block of all life on Earth, representing around 50% of the dry biomass. So how can anyone claim that releasing more carbon in the ecosystem a bad thing?

This argument isn’t logical, having too much of anything good is a bad thing. Water is even more fundamental to life, than carbon, but we all know that we need the right amount of it. Drink too much water and you’ll die, submerge a tree into water and it will die as well. This is true of all the vital nutrients that we need, we can’t live without vitamin C, but ingest too much of it and you’ll die. I think my point is clear, simply stating that carbon is vital for life doesn’t imply that we can release an unlimited amount of it in the atmosphere over an extremely short period of time without disrupting the fine balance of the ecosystem. Now let’s step out of the theory and look at some facts.

How much carbon?

How much is too much ? How much carbon have we released since the beginning of the industrial revolution? It’s hard to give a precise answer, but the estimates very between 910 and 1374 gigatons of carbon. (2) This sounds like a big number, but I bet that nobody reading this can imagine what a gigaton represents. Let me give you an example : the combined dry mass of all living organisms on Earth, all the plants, microorganisms and animals is around 550 gigatons. (3). Yes, that means that a hell of a lot carbon that was added in the atmosphere since 1850. That is a blink of an eye on a geological scale. The concentration of CO2 in the atmosphere exploded over the same period of time, check out this graph and notice how unprecedented the increase in the CO2 levels is. (4)

We’re destroying the ecosystem’s capacity to absorb the carbon

Under the right circumstances plants can benefit from some extra carbon, given the right temperature and nutrient availability, but these experiments done in greenhouse agriculture don’t translate into the real world. More on this in the detailed article (5).

To make matters even worse we’re destroying Earth’s ability to capture carbon from the atmosphere. We’ve destroyed more than half of Earth’s forests, and deforestation is not only ongoing, but accelerating, especially in the tropics. We keep on releasing more carbon into the air and we keep on hindering the ecosystem’s ability to absorb it. The tropical forests are currently emitting more carbon than they absorb (6).

The greening

NASA studies are showing (7) that the Earth is becoming greener, isn’t this proof that climate change and higher CO2 levels are beneficial for life on Earth?

This is probably the toughest part about this argument. The rising levels of CO2 are responsible for a part of the greening. The greening implies that plants are able to absorb more CO2, they absorb around half of what we add to the atmosphere every year. There are several major issues though.

Adding more CO2 will not keep on increasing the greening effect indefinitely. Plants react to the increased concentrations of CO2 quickly, but the warming of the climate stretches over decades. The benefits of CO2 fertilization will reach a plateau, while the warming that we’ve locked in will continue to increase. Warmer temperatures can help plant growth in the temperate latitudes, but are causing damage to the forests in the warm regions of the Earth. Forests are able to migrate over long periods of time, but the climate is changing too rapidly for this natural migration of plant and animal species to take place.

When we talk about tree cover, let’s not forget that it doesn’t equate bio-diverse forests. A lot of the growth is provoked by the warming climate. Tree lines are being pushed in higher altitudes and latitudes. Meanwhile, tropical forests are experiencing constant shrinkage (8). When we talk about “greening” let’s not forget that tree plantations and intensive agriculture are also “green”. Many bogus websites misrepresented the findings of a recent NASA study, which showed that a huge part of the greening observed in India and China was due to intensive agriculture and mono-culture tree plantations. Learn more about this study in my article on the topic, and be better prepared to argue against the tsunami of misinformation under most comment sections related to climate change.


The Earth is a giant greenhouse, but it’s very different than the ones we use for agriculture. People want to extrapolate that since CO2 fertilization works in agriculture, it means that it’s beneficial for the planet as a whole. Any benefit created by the increase in CO2 levels, will be negated by the rapidly changing climate. The ecosystems cannot adapt quickly enough, agriculture is also suffering from the extreme weather events provoked by the warming climate. The plants are already incapable of absorbing the CO2 that we release in the atmosphere every year, putting more CO2 is not going to change this. The build-up of greenhouse gases is going to continue, unless we take urgent and effective steps to cut our emissions. And let’s not forget that nature will end up adapting to these cataclismic changes. Life on Earth survived extreme extinction events, most of them were provoked by rapid changes in Earth’s climate. On the other hand human civilisation is fragile, if our crops start to fail, if huge swats of territory become uninhabitable, because of the rising temperatures or rising sea levels, the political, economic and social instability will plunge us into a period of unprecented migration and possibly catastrophic war over the dwindling ressources.

Check out the sources for more information. If you liked this article and you think that more people should see it, interact with the post on Facebook and share it. And if you would like to see me write more of these articles in the future, consider supporting me with a donation. It’s people like you who support my work on social media and who keep my websites independent and free from advertisements.

Sources :

(1) – Trump retweets climate denier
(2) – Total human emissions since the industrial revolution
(3) – Total weigh of the biomass
(4) – Extreme increase in CO2 levels
(5) – Effects of CO2 on terrestiral plants
(6) – Tropical forests emit more carbon than they soak
(7) – Greening effect
(8) – Rainforests shrinking due to climate change
(9) – Climate change and agriculture
(10) – Mass extinctions provoked by rapid changes in the climate

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