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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 rel
by GhostVII 8y ago
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.
- gumby 8y agoApparently most people don't understand this! There's a net loss of planting new trees, but then as you say you get stasis.
- munk-a 8y agoYou 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.
- mpg33 8y agoYou'd think large forest fires would have an impact though in terms of the regrowth.
- CGamesPlay 8y agoTree 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.
- agumonkey 8y agois it ? I thought it was mostly digested by fungi / bacteria / insects without re-emitting it
- Retric 8y agoDigestion 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.
- agumonkey 8y agoI 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 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) ?
- shaki-dora 8y agoYeah, 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.
- saalweachter 8y agoYou'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.
- abugheratwork 8y agoCarbon 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.
- amvalo 8y agoA very small fraction is sequestered as topsoil.
- sp332 8y agoA study from 2008 shows that mature forests still store some carbon. https://www.nature.com/articles/nature07276 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."
- mc32 8y agoNot 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.
- bdamm 8y agoAt 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.
- bluedino 8y agoWe'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.
- elihu 8y agoAlso fire suppression. That's become a bit of a problem, as the forests are a lot more flammable now than they were historically.
- mc32 8y agoWhile you bring up an important forestry mgmt issue (overgrowth of underbrush) I don’t think they count individual trees but rather surface area coverage.
- Amezarak 8y agoThat 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/publication-documents/2015%20Prescribed%20Fire%20Use%20Survey%20Report.pdf http://www.stateforesters.org/sites/default/files/publicatio...
- microcolonel 8y ago> 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.
- cxseven 8y agoSerious question, ignoring the other environmental impacts of logging old growth forest: Is logging carbon negative?
- autokad 8y agodepends on what those logs are for. if they are for building houses, then probably yeah
- twic 8y agoA 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: https://cbmjournal.biomedcentral.com/articles/10.1186/s13021-016-0056-7 https://cbmjournal.biomedcentral.com/articles/10.1186/s13021... 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!
- ggggtez 8y agoMost 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.
- ams6110 8y agoWhen 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.