|
Post by Belushi TD on Mar 5, 2009 19:26:46 GMT
I've a question....
I seem to remember reading in various places the following bits of data...
1. Most of the old growth forest (maybe more than 95%) was cut down by the early settlers. (I.e., pre-1850)
2. Massive tree planting efforts started in the 1930's
3. Mature forests are net emitters of CO2
4. We now have more forests in the US than we did when the first european settlers arrived.
If all these bits of info are true, (I'm not sure they are, they're just what my foggy brain remembers, and I don't have the time to look up the relavant data, I'm hoping someone out there knows the answers) then is it not possible that a chunk of the increase of CO2 in the atmosphere is due to more trees?
Corelary 1: Greenies are always going on about how we shouldn't log. Does this mean that not cutting down trees is a bad thing for AGW?
Belushi TD
|
|
birder
Level 3 Rank
Posts: 223
|
Post by birder on Mar 5, 2009 20:07:11 GMT
I googled trees and co2 and found that trees absorb co2 and emit oxygen
|
|
wylie
Level 3 Rank
Posts: 129
|
Post by wylie on Mar 5, 2009 20:15:50 GMT
Belushi,
I am PRETTY SURE (not absolutely certain) that the amount of forest that has been cleared for farming in the US greatly exceeds the amount of clearing done prior to the European colonization. It would not make sense that all the farmland that is currently under cultivation could have been maintained in that state with stone axes. The American Indian has an impressive history but they didn't have access to chain saws and their population density was a fraction of the current number.
Here is an anecdotal number: at the beginning of the 20th century, Massachusetts, one of the densest population states, had only 20% forest cover and 80% cleared land (mostly for farms). However, by the close of the 20th century, those numbers were reversed and 80% of MA is now forest. That was a result of a combination of factors, including industrialization and the mechanization of farms but also it was a policy decision to encourage tree farming. I believe that MA is the most extreme example of this in the US (not surprisingly).
It is CERTAINLY true that there is more forest in the US today (much of it young) than 50 years ago because the farming industry has shrank in terms of acreage (greatly increased in terms of total production!!!). Also, there are policy decisions to allow farmers NOT to produce and be paid (allowing farmland to revert to a more natural state).
HOWEVER, the vast majority of the old growth forest is gone. I believe the number for Canada is 90% of the old growth gone and I think the number for the US is even higher. That means that although much of the previously old growth is now forest again, most of that is NOT old growth. A truly mature forest is several hundred years old. Most of the forest in the US is less than 100 years old.
So although I don't disagree with the basic thrust of what you are suggesting (i.e. US forests are absorbing less CO2 than 50 years ago), I still believe that on balance, the US forest cover is still absorbing CO2.
Of course, I suspect that the CO2 absorption by the forests is swamped by CO2 absorption by the Ocean. Henry's Law is still a huge factor. Since the concentration of CO2 in the Oceans is a LONG way from saturation (a number of about 1% of saturation sticks in my head from Kiwi), the amount of CO2 that can absorb in the oceans will INCREASE as the amount of CO2 in the air increases. I suspect that the "Carbon sink" for the oceans is now significantly greater than it was 100 years ago because the concnetration of CO2 in the air is now 20-30% higher than it was 100 years ago. Since the temperature of the ocean hasn't changed much (takes about 800 years for the deep ocean to change), it only makes sense that the amount of CO2 being dissolved at any given time is increasing in proportion to the increase in the atmosphere.
Hope that this helps you,
Ian
|
|
|
Post by poitsplace on Mar 6, 2009 3:31:37 GMT
Corelary 1: Greenies are always going on about how we shouldn't log. Does this mean that not cutting down trees is a bad thing for AGW? Belushi TD Quite a few "green" campaigns are pop-culture garbage that end up doing the exact opposite of what they're hoping to do. In pushing their anti-nuclear agenda, they may have increased CO2 (not that it matters) and then the ACTUAL damage...it increased pollution and ironically, the amount of nuclear material entering the environment (coal often has small amounts of nuclear material in the fly ash) ...or let's not hunt some animals when we've already completely eliminated their preditors. ...or how about that biofuel?
|
|
|
Post by kiwistonewall on Mar 6, 2009 4:51:33 GMT
In pushing their anti-nuclear agenda, they may have increased CO2 (not that it matters) and then the ACTUAL damage...it increased pollution and ironically, the amount of nuclear material entering the environment (coal often has small amounts of nuclear material in the fly ash)Small amounts? It's arguably more dangerous to live near a coal plant than a nuclear power plant! Ignoring risk of terrorists & meltdown! www.sciam.com/article.cfm?id=coal-ash-is-more-radioactive-than-nuclear-waste
|
|
|
Post by slh1234 on Mar 6, 2009 6:11:26 GMT
Wylie, I don't have exact figures on any of this, but I think there may be more to reforestation than just what is done in places like Massachussetts. Mainly, because there are many more types of biomes in the US than just forest.
As an example, the 1930's brought the dust bowl to Oklahoma because of severe drought and farming in an area that really was just grasslands and plains. After that time, I now read that the agressive capture of water in ponds and lakes in that area has transformed it into "green Country" at least for the Northeastern part of that state. A lot of area that was formerly grassland is now forested with hardwoods.
In another area, the Central Valley of California is basically a desert. But with irrigation, it has been transformed into one of the highest yielding farming regions in the US. If you drive along I-5, you can see that much of that farmland is citrus groves or almond groves. That doesn't exactly fit the definition of forest that we usually think of, but the bottom line is that an area that was formerly desert is now covered in trees. As I understand, almond trees slow their bearing after a few years, so the almond farmers pull the old trees out and re-plant periodically. You can see groves that have been pulled up occasionally. So it would seem the almond groves stay pretty young.
I've heard, as the original poster said, that the US is now more heavily forested than it was when white men first arrived here. I don't know how that can be known empirically, but conversions like what has happened in Eastern Oklahoma make that at least seem possible. But I have no idea what the net effect is.
|
|
|
Post by nautonnier on Mar 6, 2009 7:23:08 GMT
I have posted this before on the 'old board' (don't hear that so often now ) • CO2 is responsible for ~9% of ‘radiative forcing’ or green house effect; • Water vapour is responsible for 35 – 70% of ‘radiative forcing’ or green house effect; • Plants have to ‘breathe’ to stay alive as well – “plant respiration releases 5 to 10 times as much carbon dioxide as fossil fuel burning” ( www.terradaily.com/reports/Of_Mice_Men_Trees_And_The_Global_Carbon_Cycle.html ) • The amount of carbon ‘locked up’ by a tree cannot exceed its total weight say 1000 kgs • A plant also transpires – it takes in water from the ground and evaporates this off through its leaves. For a mature tree in summer the rate is of the order of 200 litres AN HOUR equivalent to 200 kg of water per hour or the tree’s weight in 10 hours So what is the effect of planting a tree? If you walk through a wood or forest on a hot day - the air feels cool compared to an arid area - it is not only due to the shade but also due to the evaporation (transpiration) of water from the trees and plants. During the night the reverse occurs and the forest feels warmer - due to the higher humidity. All these deserts turned green are generating areas of higher humidity that have a strong and continual radiative forcing effect that is far in excess of the CO 2 that the plants take in as part of photosynthesis. The amount of water required to do this by definition is not available naturally - that's why the areas were originally desert or sparse grassland. In many cases these arid areas are irrigated from very deep wells that are used to access aquifers that contain what is called 'fossil water' as the water was last rained many thousands of years ago. In some areas of India so much water has been extracted that the aquifers are going briny as sea water is drawn in. (Google: irrigation "cubic kilometer" "fossil water" ) The amount of water being continually evaporated into the atmosphere by irrigation/transpiration dwarfs the amount of CO 2 from fossil fuels and remember when fossil fuels (hydrocarbons) are burnt there is also more H 2O generated than CO 2.
|
|
|
Post by steve on Mar 6, 2009 11:25:45 GMT
|
|
|
Post by nautonnier on Mar 6, 2009 17:24:31 GMT
This is actually saying the same - albeit in a different way. A mature tree _does_ sequester some carbon (I will hold back on whether that actually affects climate) and if you let the tree die and rot - then that carbon or some of it - will be released into the system again. But that mature tree cannot sequester more than its own weight in carbon. So the best that will happen is that it will reach its adult height - and then its kept alive so it does not rot. However, that tree will now be respiring more CO 2 than it takes in through photosynthesis as it is no longer growing. The amounts and proportions will vary from plant to plant deciduous to evergreen, xerophytes to hydrophyte but the overall logic is the same. Added to that the plant will be transpiring water into the atmosphere - in the Amazon with all the heat this transpiration is sufficient to ensure rain from the transpired water in the Amazon basin. This also means that if you slash and burn the mature vegetation less water is transpired into the atmosphere and there is less rain - at some stage of slash and burn this will lead to a desertification of the Amazon basin. I think that this may be one of the reasons for this article.
|
|
|
Post by poitsplace on Mar 6, 2009 17:43:30 GMT
This is actually saying the same - albeit in a different way. A mature tree _does_ sequester some carbon (I will hold back on whether that actually affects climate) and if you let the tree die and rot - then that carbon or some of it - will be released into the system again. But that mature tree cannot sequester more than its own weight in carbon. So the best that will happen is that it will reach its adult height - and then its kept alive so it does not rot. However, that tree will now be respiring more CO 2 than it takes in through photosynthesis as it is no longer growing. The amounts and proportions will vary from plant to plant deciduous to evergreen, xerophytes to hydrophyte but the overall logic is the same. So what you're saying is that the best way sequester the carbon would be to raze the forrest at or shortly after it's peak growth period and bury the trees (like say...as paper in a landfill) and plant a new one. Sort of like the way we do with the 24 million acres of tree farms we currently have in the US.
|
|
|
Post by nautonnier on Mar 6, 2009 19:26:03 GMT
This is actually saying the same - albeit in a different way. A mature tree _does_ sequester some carbon (I will hold back on whether that actually affects climate) and if you let the tree die and rot - then that carbon or some of it - will be released into the system again. But that mature tree cannot sequester more than its own weight in carbon. So the best that will happen is that it will reach its adult height - and then its kept alive so it does not rot. However, that tree will now be respiring more CO 2 than it takes in through photosynthesis as it is no longer growing. The amounts and proportions will vary from plant to plant deciduous to evergreen, xerophytes to hydrophyte but the overall logic is the same. So what you're saying is that the best way sequester the carbon would be to raze the forrest at or shortly after it's peak growth period and bury the trees (like say...as paper in a landfill) and plant a new one. Sort of like the way we do with the 24 million acres of tree farms we currently have in the US. Exactly, and that has been proposed with burial of the 'razed' trees in boggy ground or below the water table to prevent them rotting with aerobic bacteria that would just assist in releasing the carbon back into the system. If the print media continues to go to the wall as everyone is reading them online now- the amount of landfill paper may reduce considerably - so the process can be shortcut and the trees put straight into landfill
|
|
|
Post by heatsink on Mar 6, 2009 21:50:34 GMT
Quoted in the article, Professor Oliver Phillips says, "If the earth's carbon sinks slow or go into reverse, as our results show is possible, carbon dioxide levels will rise even faster. Deeper cuts in emissions will be required to stabilise our climate." I'm not sure I understand his reasoning. Let's assume that Co2 doubles over the next 10 years starting from 390ppm. Let's also assume that humanity becomes a carbon sink and removes two time all the Co2 that we have ever put in to the atmosphere without adding any. What would the final Co2 ppm be? Assuming IPCC is correct, how much of an impact will the human Co2 sink have on temperature?
|
|
|
Post by heatsink on Mar 6, 2009 21:54:52 GMT
This is actually saying the same - albeit in a different way. A mature tree _does_ sequester some carbon (I will hold back on whether that actually affects climate) and if you let the tree die and rot - then that carbon or some of it - will be released into the system again. But that mature tree cannot sequester more than its own weight in carbon. So the best that will happen is that it will reach its adult height - and then its kept alive so it does not rot. However, that tree will now be respiring more CO 2 than it takes in through photosynthesis as it is no longer growing. The amounts and proportions will vary from plant to plant deciduous to evergreen, xerophytes to hydrophyte but the overall logic is the same. So what you're saying is that the best way sequester the carbon would be to raze the forrest at or shortly after it's peak growth period and bury the trees (like say...as paper in a landfill) and plant a new one. Sort of like the way we do with the 24 million acres of tree farms we currently have in the US. Sounds like all mature trees should be cut down and buried. Harboring a mature tree should be punished by fine and prison time - preferably a large fine.
|
|
|
Post by jorgekafkazar on Mar 7, 2009 0:22:27 GMT
Or maybe we should all live in log cabins. That will sure fit in with the greenies pipe dream of utopia.
|
|
|
Post by hiddigeigei on Mar 7, 2009 4:10:36 GMT
3. Mature forests are net emitters of CO2
TWO COMMENTS:
All living cells respire continually (break down carbohydrate into water and CO2). A temporate mature tree photosynthesizes to produce and replace leaves, maintain its living structure, and store sugars for nights and winter. Much production is lost when it drops its leaves, but it is still a net producer of carbohydrates unless it is dying. The leaves, litter, frass, pollen, seeds, etc. are mostly (but not entirely) metabolized by bacteria, fungi, and inverts; but it was all fixed by the tree from CO2 originally, so the mature forest is still a net collector of atmospheric carbon.
When the Shenandoah Valley was first seen by Europeans, it was nearly treeless. The Indians burnt it periodically to provide pasture for their large game animals.
|
|