[oori]

Very interesting article. Quote:

Many pine trees in managed forests, such as the European spruce, take roughly 80 years to reach maturity, being net absorbers of carbon during those years of growth – but once they reach maturity, they shed roughly as much carbon through the decomposition of needles and fallen branches as they absorb. As was the case in Austria in the 1990s, plummeting demand for paper and wood saw huge swathes of managed forests globally fall into disuse. Rather than return to pristine wilderness, these monocrops cover forest floors in acidic pine needles and dead branches. Canada's great forests for example have actually emitted more carbon than they absorb since 2001, thanks to mature trees no longer being actively felled. Arguably, the best form of carbon sequestration is to chop down trees: to restore our sustainable, managed forests, and use the resulting wood as a building material. Managed forests certified by the Forest Stewardship Council (FSC) typically plant two to three trees for every tree felled – meaning the more demand there is for wood, the greater the growth in both forest cover and CO2-hungry young trees.

[mrob]

Even if there's no demand for wood, the trees should still be harvested because they can be pyrolized to produce fuel gas/oil and biochar. About 50% of the carbon can be converted to biochar, which is both a valuable soil amendment and a way to long-term sequester carbon such that it can't be easily extracted. And the carbon released by burning the remainder would have been released to the atmosphere away as the trees decayed, so it's better it does something useful.

https://en.wikipedia.org/wiki/Biochar

[YayamiOmate]

Do you say its an efficient battery for solar power?

[mrob]

My guess is probably not, because photosynthesis is not very efficient. See https://en.wikipedia.org/wiki/Photosynthetic_efficiency

But if the trees are already grown then I think we should use them, and not just leave them to rot.

[YayamiOmate]

Its an obvious tautology to me.

If you allow decomposition then obvioisly net must be zero. If you createa object and destroy it, it pretty much has to release its source material in some form.

If tree stops growing it obviously has to have zero net. Anything absorbing anything has either to store it - grow, or release it in some form. Carbon is element, what are the options? Store it permanently, transform chemically and release, or transform it atomically and change the element but tree is not a nuclear plant.

[TomMarius]

As long as it's wood, it's emission negative

[quixoticelixer-]

That's not quite true, it takes a lot longer than 80 years for forests to stop sequestering CO2, even for fast growing species.

[lmilcin]

"On average", no forest produces or consumes any CO2 or O2 unless the biomass is somehow sequestered, for example buried under volcanic ash or on the bottom of anoxic lake which would typically prevent it from decomposing.

The forest binds some amount of carbon and oxygen for a time being but then it is released back when it burns or decomposes, etc. It is really insignificant when compared with steady flow of carbon from fossil fuels.

[bluGill]

That isn't completely true. A well managed forest will sequester some carbon when it burns. Note well managed in there, that means a small fire every year, a large fire gets hot enough to burn all the carbon, but a small fire will burn only part of the carbon and leave the rest as charcoal. Moral: shoot smokey the bear and let foresters start the fires they want to if only they were allowed to.

Of course the above is a generalization, and as all of them false in some way. Ask your local forester what applies to the forest in your area, but don't try to apply it to a forest in the next neighborhood as that might be different.

[lmilcin]

To sequester carbon it would have to be prevented from decomposing. It is not enough for the trees to turn to charcoal during fire. If what you said was true "well managed" forest would be standing atop of layers of charcoal which obviously is not true.

Instead what I suspect happens is that the charcoal from fires weathers, crumbles and becomes part of the soil. Soil is feed for other organisms.

[bluGill]

The charcoal is mixed in with soil, it is there.

[ARandomerDude]

I don't think that was the argument. OP was saying after maturity the scales tip to being net emitters.

[quixoticelixer-]

They don't really ever change to be net emmitters, and it takes a long time for them to stop absorbing carbon ( a few hundred years)

[benj111]

Do you have a source? Because you're directly contradicting the article.

[aukust]

Anecdotal evidence suggests to me that European spruce stores more CO2 than it sheds way over 80 years old as a spruce grows in mass significantly decades after reaching that age.

However here is a study that tries to bring some light to carbon pools on over-mature 167-213 year-old trees: https://www.mdpi.com/1999-4907/9/7/435/pdf

[bryanlarsen]

Anecdotal evidence tells me that spruce trees are really good at suppressing undergrowth due to their acidic needless so claiming a mature first is a net emitter makes sense to me. The trees may be growing, but nothing else is.

[garmaine]

You don’t need a source. To be a net emitter the tree would have to be losing mass. That’s not what healthy trees do, even old ones.

I believe the article might have been trying to say is that trees tend to die and decompose (or burn) which makes them carbon emitters.

[benj111]

You're talking about individual trees though.

Theres plenty of mechanisms where the individual trees grow, but the forest holds less carbon.

The linked article [1] mentions forest fires and insect infestations.

[1] https://www.cbc.ca/news/canada/calgary/canada-forests-carbon...

[Robotbeat]

That’s not true. Methane is a significantly more potent greenhouse gas than CO2, so if the tree is absorbing CO2 but the decomposing needles and leaves are emitting methane, it could easily be a net GHG emitter.

[jefftk]

If a tree keeps growing, but also gets more successful at suppressing growth of it's neighbors, then it can be a net emitter overall even though it's a net absorber considered individually.

[quixoticelixer-]

Wardle, P. (1991). Vegetation of New Zealand. Cambridge: Cambridge University Press.

If I have time tomorrow i'll find the page.

[benj111]

Is it possible we're talking about different things? You talking about individual trees and the article talking about forests as a whole.

[mywittyname]

Governments should pay to have the mature trees harvested, then tossed into some body of water, and eventually covered with dirt. At that point, the carbon sequestration will last for a 1000+ years.

Should demand ever increase, then the felled trees could be reharvested, cured, then used as normal.

[mistrial9]

.. it is not "plummeting demand" .. it is a bump in the massive consumption growth curve of the modern age.. aside from that, all paths need to be considered.