I often hear science-adjacent folks stating that a tree needs to be 30 years old before it starts absorbing CO₂, usually paired with the statement that it’s therefore pointless to start planting tons of trees now for slowing climate change.
Now, as far as my understanding goes, the former statement is very obviously nonsense. As soon as a tree does photosynthesis, it takes carbon out of the air, which it uses to construct cellulose, which is what wood is made of.
Really, it seems like it would absorb most CO₂ during its initial growth.
I understand that it needs to not be hacked down + burnt, for it to actually store the carbon. But that would still mean, we can plant trees now and not-hack-them-down later.
I also understand that some CO₂ invest may be necessary for actually planting the trees, but it would surprise me, if this takes 30 years to reclaim.
So, where does this number come from and is it being interpreted correctly? Or am I missing something?
Edit: People here seem to be entirely unfamiliar with the number. It might be that I’ve always heard it from the same person over the years (e.g. in this German video).
That person is a scientist and they definitely should know the fundamentals of trees, but it was usually an offhand comment, so maybe they oversimplified.
They may respire, but they must absorb more than they respire, because that’s where the wood comes from…
Not necessarily. The two things aren’t related. You yourself burn way more calories in a year than you store in your body or use for growth. Respiration is not just about growing. It’s about using energy for cellular processes: immune system, transporting chemicals around the organism, replacing old cells.
An organism can grow at one rate and use energy (expelling CO2) for other functions at a different rate. They aren’t really related.
They are related, because the energy they use and the mass they grow both come from absorbed CO2.
In other words, every molecule of CO2 expelled by a tree was previously absorbed by the tree. Unlike humans, energy use by trees is carbon neutral. Which means trees cannot grow unless they absorb more CO2 than they expel.
I’m not sure, why you’re interpreting my comment as a general statement. I’m specifically talking about trees. While it’s theoretically possible that they get carbon from the ground and actually respire more into the air than they absorb, while also growing wood, that would be extremely surprising to me. Unless there’s data supporting it, I don’t see why we should entertain the thought…
On average they emit around half the carbon they absorb so this wouldn’t explain that fact.
It’s almost definitely false.
That makes no sense. The human body is on average carbon neutral. You eat carbon and then you excrete it. Same as trees. Except you don’t continuously grow like a tree for potentially centuries.