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Canada's forests emit more carbon than they absorb (cbc.ca)
124 points by colinprince 34 days ago | hide | past | web | favorite | 83 comments

I'm not sure what the author is playing at, but I think at the very least he is trying to be a bit clever.

His argument is based upon that forest biomass is shrinking and therefore forest are causing CO2 emissions:

"When you add up both the absorption and emission, Canada's forests haven't been a net carbon sink since 2001. Due largely to forest fires and insect infestations, the trees have actually added to our country's greenhouse gas emissions for each of the past 15 years on record."

Forest only reduce CO2 when they photosynthesising, so if the forests are being killed by fire or insects, then the forests are not ingesting CO2 but are expelling.

They way this article is titled leads one to believe that forests are causing the problem and that it is implicitly okay to be reducing forest biomass. I think the title is misleading and disingenuous.

For what it's worth, I did not misinterpret the title as you suggest, although I had enough background to know what's going on. What title would you suggest in roughly that amount of space?

> What title would you suggest in roughly that amount of space?

I'll try! something like this would be my offer:

> Canadian forests net carbon emitters due to biomass loss

vs the original

> Canada's forests emit more carbon than they absorb

close enough for me

Losses of Canadian forest resulted in net carbon emmissions

I like this, although it's a bit ambiguous whether it's the forests or Canada as a whole that experienced a "net carbon emmissions".

That is an ambiguity that is fine to write the story about. At least when the headline readers start posting the headline on Reddit others will know that there is an ambiguity to clear up.

Your basic premise is wrong. A forest that is photosynthesizing is not a carbon sink. Once a forest reaches a steady state and births are balanced by deaths the forest becomes carbon neutral. For every ton of new tree, an old tree dies, rots(slow)/burns down(fast), and releases it's carbon back into the ecosystem. Otherwise known as the carbon cycle.

So sure taking a million acres of trees and cutting them down, burning them, and putting building on them releases significant carbon... once. Similarly taking a million acres of desert and turning it into a forest will consume CO2 for 50 year or however long it takes to reach a steady state.

It's difficult to fit nuance into such a small title. And titles are not supposed to convey the entire message -- if they did, what would be the point of the article?

I understand where you are coming from, but that title is pointed, topical, and expanded upon in detail throughout the article.

"Damage to Canada's forests makes them emit more carbon than they absorb"


And the forest fires and beetle vulnerability are not unrelated to current climate change (at least in California last I read), so that might help close the non-anthro-centricity argument they are using for different accounting methods.

Yeah, I'll concede that's pretty good.

True, but it also shouldn't be misleading. How many will just repeat the headline as a blanket statement but not read into it further?

The title should be changed, as it could be doing more damage than good...

Forest fires and logging are net carbon emitters.

I don't think this should be too surprising. Forests don't destroy carbon, just store it in the form of trees. When the trees decompose, or burn down, it is released again. So for a mature forest you would expect it to have around net 0 emissions. As far as I know the main way a forest can be a carbon sink is if it is expanding, which I don't think Canada's forests are doing.

A study from 2008 shows that mature forests still store some carbon. https://www.nature.com/articles/nature07276 "We find that in forests between 15 and 800 years of age, ... forests can continue to accumulate carbon, contrary to the long-standing view that they are carbon neutral."

Not sure about Canada, but my understanding is that for the US we’ve gained forests compared to 50 or 100 years ago due to replanting, repurposing land and having dedicated paper pulp tree farms.

At least in BC, replanting and tree farming are alive and well and have been for many decades. There are in fact many places where second generation has been logged and third generation is in growth.

Also fire suppression. That's become a bit of a problem, as the forests are a lot more flammable now than they were historically.

That really depends on the state/region. You can see in this [1] report that states like Florida and Georgia are burning millions of acres a year in prescribed burns, while California burns a few ten thousand.

[1] http://www.stateforesters.org/sites/default/files/publicatio...

While you bring up an important forestry mgmt issue (overgrowth of underbrush) I don’t think they count individual trees but rather surface area coverage.

We're still nowhere near we were before the lumber boom of the mid to late-1800's. Tens of thousands of square miles were clearcut for lumber and cities are in their place now.

When trees decay, a certain portion of the material remains solid and eventually becomes part of the soil layer. Also when trees burn, a certain amount stays as carbon/charcoal/ash in the ground. So while some of the carbon is released when trees decay or burn, not all of it is. So I would expect a mature forest to be a carbon sink, though not necessarily a huge one.

Apparently most people don't understand this!

There's a net loss of planting new trees, but then as you say you get stasis.

You don't get stasis, but the rate of carbon absorption drops, when trees die in the forest some of the carbon that was sequestered gets retained in the soil, most will decompose back into the atmosphere but the slow growth of soil in a forest is tied to nutrients that are being isolated out of the environmental cycle.

Most forests in North America are not mature. Consider how tall redwood trees can get. Also, trees are converted into wood and paper. Generally that wood isn't burned and returned to the atmosphere.

Why not suggest the whole planet is carbon neutral at that point? It is meaningless because we only care about the carbon in the atmosphere.

A very small fraction is sequestered as topsoil.

You'd think large forest fires would have an impact though in terms of the regrowth.

Tree growth and forest fires are just moving carbon back and forth between the air, soil, and trees. You can’t simply “destroy” the carbon, you have to keep it somewhere. Similarly, humans aren’t “creating” carbon, we are just taking it out of the oil it was in and putting it into the air.

is it ? I thought it was mostly digested by fungi / bacteria / insects without re-emitting it

Digestion breaks things down for energy which means producing CO2. You can simplify organic chemistry on these scales as spending energy to store carbon or gaining energy to release it.

In some situations you can get net carbon storage which is how we got fossil fuels in the first place, but this is really slow. On the order of 1 Billionth the total fossil fuels stored per year.

I asked below but maybe you'll know the answer. Basically insects/bacteria cellular respiration produces CO2 just like us ?

update: found some answer https://www.amentsoc.org/insects/fact-files/respiration.html

I never considered that.

Also, how unlikely that this CO2 is reabsorbed by the plants (granted that can only occur after winter when leaves are back) ?

Yeah, of course. Bacteria, insects, fungi, and any animal break down plant matter (fruits, salads, wood), releasing CO2 in the process. Fire does the same, only the energy is emitted as heat and light, not movement and wasting time on HN.

CO2 + sunlight is again converted into organic material by plants (and some bacteria). It really doesn’t matter if it’s the „same“.

This is the basic carbon cycle.

You'll get a residue of organic materials that don't immediately return to the atmosphere, and eventually accumulate into fossil fuels, but that's a very slow accumulation, a fraction of the carbon that is initially captured when a unit of forest grows from scratch.

Carbon is an element. Most organisms to a lot of chemical rearrangement of the element, but the element is not created or destroyed in biological processes. Any carbon kept during life is released at death.

But not necessarily released as CO2, which is what "re-emitted" means to me. If it goes atmosphere -> tree -> fungus -> bits of fungus buried in the ground for millions of years, that's effective sequestration.

It may well be, but that's not what happens to most of the wood in trees— most of it rots (CO2 released slowly by the organisms consuming the wood) or burns (CO2 released by combustion).

This is true only in part.

We have found shells, made of Calcium carbonate, still relatively intact more than 3000 years after the death of the animal. Some shells had last for 500000 years (See Nature 2014-dec-03)

Under the sea there are entire ecosystems based in dead shells.

As said below, it's not C, but CO2 we were worried about. Also I admit that I don't know if humus organism produce CO2 from wood remains.

> As far as I know the main way a forest can be a carbon sink is if it is expanding, which I don't think Canada's forests are doing.

The way you keep a forest expanding is by logging it.

Serious question, ignoring the other environmental impacts of logging old growth forest:

Is logging carbon negative?

A quick google suggests that this is an active research topic. I have only skimmed this paper, but they find that logging is net emitter of CO2:


Interestingly, they account for carbon emission from the wood produced by logging ("sawnwood"):

Sawnwood decay is approximated with an exponential decay [with a half-life of] the normal distribution truncated at zero with mean equal to 30 and standard deviation equal to 15, according to IPCC guidelines. So far, no life cycle analysis has yet been done for woody products in the tropics and adapting the framework developed in Europe and North America in tropical countries remains challenging.

So they assume that the average bit of timber lasts thirty years before giving up its carbon, and only about one in six lasts longer than 45 years. I suppose the lifecycle of wooden manufactured items tends to end with them being burnt when they're worn out.

If i am reading the graphs correctly, then wood going to the sawmill is only a small part of the carbon emitted by forestry, and they mention that only one-third of the wood entering a sawmill leaves as sawnwood, the rest being lost as sawdust, so even if you could preserve wooden items for ever, it might not move the needle much.

On the other hand, if you could collect all the sawdust from the mill and bury it, or make it into biochar and then use it as a soil amendment, that might.

Anyway, that is one paper amongst many, go forth and read if you're interested!

> So they assume that the average bit of timber lasts thirty years before giving up its carbon, and only about one in six lasts longer than 45 years. I suppose the lifecycle of wooden manufactured items tends to end with them being burnt when they're worn out.

That seems like a pretty bizarre set of assumptions. Wood doesn't just disappear in 45 years unless you leave it in the open untreated.

As i wrote in the paragraph you quote, my assumption is that this models wooden items being burnt at the end of their useful lives.

But hey, don't take my word for it - in the paper, that bit references this:

Penman J, Gytarsky M, Hiraishi T, Krug T. Good practice guidance for land use, land-use change and forestry. Intergovernmental Panel on Climate Change (IPCC), chapter 3, Appendix 3.A.1.3. UNEP; 2003. p. 268–70.

Which you can read here:



So dive into the gory details of harvested wood products, and the basis for their future methodological development to your heart's content!

Sorry, didn't mean to come off passive aggressive. I'm here in good faith just like you.

It sounds like the answer basically depends on how we log and what we do with the produce, but it could be made carbon neutral or even negative with the right approach.

Makes me wonder just how much polymer use we could replace with wood, and what kind of disposal techniques for it we could develop to increase carbon sequestration (e.g. instead of burning it, bury it deep?).

There needs to be more talk about biochar...

depends on what those logs are for. if they are for building houses, then probably yeah

Well, then it is not the forest itself. It is the humans managing the forest, if I've understood correctly.

fta, recent fires and pests.

Caused by global warming (human?), fta.

The term "global warming" appears nowhere in tfa. That of course does not mean it isn't the case but it does mean that you are mistaken.

You are correct, I misattributed the top comment as part of the article, was an honest mistake.

"Old growth forests tend to exist in a carbon steady state; younger, growing forests tend to be net carbon uptakers. This situation is due to natural disturbance regimes in forests, like fire and pine beetle, having historically signifiant impacts in large part because of climate change."

Peservation of mass holds as it always did. The forest only absorbs CO2 if the total mass of the trees grows. For a mature foest this is usually not the case.

Trees don't stop growing. Trees also die, fall to the forest floor, and a % of the carbon is released as CO2 during decomposition but the remaining % is retained as soil. The coal we mine to burn is from the retained % of ancient forests. The oil we drill to burn is from the retained % of algae and plankton that ended up trapped under rock and essentially pressure cooked into oil.

Semi-serious question: should a country have to account for volcanos in its territory as well?

Volcanoes are part of the natural CO2 cycle, which is in balance. So adding volcanoes would be like adding the CO2 animals, including humans, exhale. The problem is that we are adding more CO2 to the cycle, disturbing the balance.

Since it only was a semi-serious question I'll assume you knew this, but I still think the balance is a good argument to have when you run into deniers.

Do volcanos emit CO2?

Yes but they also emit ash which has cooling effects.

More critically, they emit huge amounts of sulphuric compounds, which are what really sick around and tend to cooling. Unfortunately when those same compounds don’t reach high altitudes, you get a lot of acid rain. All told however, their net effect is strongly cooling over the first few years, and then milde cooling over longer time frames.

Why cooling though? It makes sense that it cools the ground, but the sunlight is still captured by the particles (as opposed to reflected by snow/water, on average), so the total Earth+atmosphere should be warmer?

Fantastic, thanks for the explanation. Can you please point me to a source? Need to send it to my dad who taught me everything I know but has now turned into a climate change denialist who says it's all a globalist / marxist / leftist plot to make money off solar panels.

Absolutely, and I wish you the best of luck in representing your views to your father. I know how painful such a disconnect can be.

This is a good intro to the broad issue of volcanoes and climate: http://www.cotf.edu/ete/modules/volcanoes/vclimate.html

A more in-depth treatment of sulfur aerosols in the upper atmosphere: https://en.m.wikipedia.org/wiki/Stratospheric_sulfur_aerosol...

Here’s a breakdown of all the gasses typically releases during eruptions and their various effects: http://volcanology.geol.ucsb.edu/gas.htm

If there’s anything else I can do, please don’t hesitate to ask.

Thank you so much! I will send them all three. Just because you offered and you seem so knowledgeable, he has also claimed the CFC damage to the ozone layer was a hoax created to promote alternative refrigerants... If you have anything on that I could use a link as well!

My pleasure, and I have a great link that goes into the exact mechanism of how CFC photochemistry destroys the ozone layer.


Here’s one with more technical analysis along with the exact chemistry:


Here’s a broad overview with historical perspectives from the American Chemical Society: https://www.acs.org/content/acs/en/education/whatischemistry...

I hope this helps.

Reminds me of global dimming.


Right now they don't even account for the factories in its territory...


Not appropriate to say that is a stupid question.

TIL, very creative = stupid.

I wonder if petrifying trees after they absorbed CO2 would help our emissions problems?

In the Carboniferous period[2], plants evolved lignin which made their cell walls stronger so they could grow taller. Fungi that could eat lignin had not evolved yet and so the the dead trees just built up layer after layer. This build up eventually turned into the coal we mine today.

Turning trees into charcoal[1] is one way to slow down the processes of the wood turning back into CO2, but it would be difficult to do it on a large enough scale.

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

No; petrified wood is the same as other fossils: it is minerals, such as silica, which has filled in the void in the earth left after the organic material has decayed.

You can still bury the wood in an environment that does not allow it to (quickly) decay, or you can simply make a lot of stuff out of wood. (If you go the second route, you'll want to ensure that your wood structures last a long time, you'll want to increase the total wood sitting around in the world, and once you reach a new plateau in the amount of wood products in semi-permanent existence, you'll stop sequestering new CO2 via the process of consumerism, new products and structures will just be re-sequestering the carbon lost from old structures and products as they decay or are destroyed.)

How long they decay wouldn't matter that much if you have the disposal process. The amount you'd end up processing every year would still be the same (reflecting total usage at any given isntant) once you get past the initial ramp-up.

The duration is important because you can only grow and harvest a finite amount of wood each year, because trees can only grow so fast. So if you harvest the maximum amount of wood possible each year, W, and it lasts for 10 years, you have sequestered 10 x W units of carbon; if you use it in ways that lasts 20 years before it needs to be replaced, you have sequestered 20 x W units of carbon.

Yes, it would.

But if you are turning trees into coal, and burying them, why on Earth are you also digging up coal, to burn it?

Sequestration is going to be far more work then simply not generating emissions in the first place.

We need to do both in order to prevent a civilization ending catastrophe. Sequestration has the advantage of allowing our net carbon output to be negative. Obviously getting to zero is the first goal, but we are already past the point where that would be enough.

Tell me if this is incorrect thinking:

An advantage of sequestration is location. Something like you can emit the CO2 in a distributed manner (think car tail pipes) and then sequester it nearby but in aggregate (think a facility just outside city limits)

The problem is that, in a market economy, like the one we live in, we can dig up and burn coal much faster then we can grow and bury trees.

Coal can be mined for $30/tonne. That's 3 cents/kilogram. At that price point, it's nearly free. How can you keep up with sequesteration, when you are competing with nearly-free?

Sequestration makes sense when we are talking about an economy that derives ~5-10% of its energy from liquid fossil fuels, and everything else from renewables. It doesn't make much sense when 50% of energy generation comes from fossil fuels. It's just too labour intensive to make it work.

Not just a market economy - a market economy that does not account for externalities, like carbon emissions in the atmosphere.

> why on Earth are you also digging up coal, to burn it?

That is a good question regardless.

If you could do that in a net energy negative way that would be something.

Yes, one of the proposed sequestering techniques is to produce and sequester biochar, essentially charcoal produced from biomass.

fun fact: many trees at around 30 years of age, become carbon positive, releasing more carbon than they absorb.

TL;DR: stock vs. flow.

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