David Roberts strongly objected to a critique of offsets and especially of credits for tree planting. The critique was originally made in the comments section of a post on a "carbon neutral" Super Bowl.
Bruce Sterling chimed in, noting that nobody can compete for purity with the dead. This is first rate irony, but unless the intention is that no one should ever criticize false solutions, no matter how wrongheaded, it only has bite if the solutions critiqued actually work. Tree planting may do all sorts of good things, but outside the tropics, it is not a significant way to fight global warming.
Let's start by looking at the Livermore study (PDF) showing that tree planting outside of tropical zones does not result in net cooling. The key here is albedo -- reflectivity of light. Trees are darker than the grass they replace. (If soil is wet and fertile enough for trees but does not have them, odds are there will be grass or other ground cover.)
So, more sunlight is converted into the long-wave radiation that greenhouse gases trap. A number of commentators on the Super Bowl post sneered at the idea that albedo can significantly affect global warming. But it is a known feedback, and one of the ways the melting of the icecaps speeds climate chaos. At the low level of potential sequestration we are talking about it is significant.
In the tropics, conditions are different. In the intense sun of that environment, tree photosynthesis is far superior to grass photosynthesis; also, trees transpire more than grass. (Transpiration is a process whereby plants emit water vapor -- as part of the circulation of nutrients, but also for cooling purposes.)
There are still problems with the tree plantations that are the most common form of tree planting in the tropics. In terms of global warming, these problems include the fact that the trees are often replacing other trees, and they are often harvested. In terms of other ecological effects, these plantations are usually monocultures, reducing biodiversity. In terms of human effects, local inhabitants are often thrown off their land to make way for these plantations. However, not all tropical tree planting is in such plantations; tree planting can make real contributions to tropical life. (Even then, carbon credits are not the right way to encourage tree planting: more on this later.)
Now is this rock solid consensus science? No; though I will note it was peer reviewed before publication, and a year after publication has stood up to all criticism so far. But I would compare critiques made of the net energy of corn ethanol. Even if corn ethanol produces a tiny amount of net energy, the difference between net input and output is so small that you would be much better off investing the money in other things. (Cellulosic ethanol is an entirely different story.) At the moment, the argument that planting trees outside the tropics results in net warming has not been refuted. But even if it is, I suspect the refutation won't show any large net sequestration. I predict that any successful rebuttal will show such a small net sequestration per tree that you can gain much greater reductions by investing money in expensive PV electricity generation. In fact, I will bet a Super Bowl t-shirt on that, if anyone is interested in a wager.
Note, by the way, that this is not an argument for cutting down existing trees, which contain decades or centuries of stored carbon. It is not even an argument against planting trees outside the tropics. (Net heating is very small and can easily be compensated for by other types of savings.) It is an argument against planting new trees outside the tropics with fighting global warming as the main goal. It is simple realism not to do what doesn't work, or attribute some virtue to a process that it does not possess.
Offsets in general are a really poor idea, but even where trees do sequester carbon, offset credits from trees are an especially bad idea. First, most tree offsets (including those purchased for the Super Bowl) are planted after purchase. That means you emit, now, and the offset occurs over the decades that follow. Even if the sequestration is calculated correctly, feedback from carbon emissions ensures that this results in a net loss. That is, you emit X amount of carbon. This results in Y additional feedback. But you only offset X.
Worse, the offset numbers can't be right. The problem is that carbon fixation in plant matter varies a lot -- between species, between the same species in differing micro-climates and soil, between the same trees at differing times. You really can't predict how much carbon a tree sequesters. If you can't put a number on it, it still might be a good idea to encourage it. But if you can't put a number on it, it is a really bad idea to use like a medieval indulgence, an excuse for emitting carbon elsewhere.
This is a problem with offsets in general. With offsets, even production of renewable energy, you can't know how much would have been done in any case. This is known as the "additionality" problem, because no one knows how much additional reduction you are gaining. Further, since we don't have the ability to visit alternate worlds and see what would have happened, we will never know. So when you grant someone credit for a quarter ton of emission reductions, and someone buys that and uses it to emit a quarter ton of CO2, you never know whether you have really broken even or whether you have actually increased net emissions. Both buyer and seller have a strong incentive to assume that the result is a wash; we have no certain way to detect whether their guess is correct or not. So emission credits are the ultimate contradiction -- a market mechanism trying to work without feedback; price signaling that does not convey information.
I have problems with emission trading in general. But when someone has a target they must comply with, and can generate credits only by exceeding that target, at least you're selling something measurable. In comparison, project-based offsets are a nightmare; there is really no feedback beyond the market collapsing from too much counterfeit currency.
Tree planting and encouraging renewables are both good things. But they don't offset carbon emissions, and should not be hyped as doing so by an environmental magazine. Oranges are healthy and good tasting. But they are not a significant protein source. Your local nutritionist can expect criticism if they say otherwise.
Comments
View as Flat
kmp Posted 4:43 am
26 Jan 2007
The key here is albedo -- reflectivity of light. Trees are darker than the grass they replace.
What if the trees are replacing the asphalt of a deserted city lot, are adding shade to city sidewalks, are part of a restoration effort of a landscape scarred by wildfire? Would these tree plantings still be considered to produce a net warming effect?
I'm still not sure I'm buying the significance of the albedo issue. Granted, I'm not a forestry scientist, so should have no rights to question the conclusions of the paper... yet, it just doesn't make sense to me. By that logic, Maine, which has tons and tons of dark, leafy trees, should be warmer than Kansas, which is flat prairie land. No?
FWIW, I did not take David's post as anger that Gristmill posters disagreed with him. I read it as annoyance at the tone of the posts... instead of a glass-half-full viewpoint, like "Hey, it's great that the NFL are recognizing global warming and want to do something about mitigating their impact. However, with the inherent problems of tree planting & carbon offsets, I wish they had considered...... (XYZ great idea that would contribute to mitigating the SuperBowl's greenhouse gas effects)" the tone of many of the comments, on that and other threads, was, IMO, a bit nitpicky and superior. I do not presume to speak for David, because, clearly, he is perfectly capable of doing that for himself; perhaps I am merely projecting my own feelings regarding those posts into his comments. For me, the bottom line is that we all love great debate and the sharing of ideas - otherwise we would not be here. It is fabulous that we have this forum in which to exchange ideas, witticisms, compliments and insults with each other - the other side of the fabulous Internet coin is the utter lack of expression it gives to our words, leaving many statements wide open to the reader's interpretation.
Kaela
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Tom Philpott Posted 5:06 am
26 Jan 2007
But whatever, Dave's rant was funny, true in its way, and there's no need to make too much of it.
Victual Reality
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sunflower Posted 5:14 am
26 Jan 2007
My greatest fear is that passion will flame out and we all become flat, quiet, accepting death as it is.
My passion is on fire.
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Backcut Posted 5:27 am
26 Jan 2007
It can be VERY difficult to produce sarcastic messages on the Internet that people will identify as not being exactly serious.
The "holier than thou Gaia-ists" often take their beliefs too far and come across as religious extremists, at times. If you want to practice fundamentalist human ecology and idealistic dogma drama, feel free to live in your adobe huts, eschew modern conveniences and fiddle with your (eco) rosaries (with apologies to Tom Lehrer).
Sometimes we all have to laugh to keep from crying, folks.
Scenic pics at http://Lhfotoware.blogspot.com
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Backcut Posted 5:35 am
26 Jan 2007
The big picture says that we CAN do things to help our forests survive, and that includes thinning projects that cut some trees and brush, making it ready for a regular program of controlled beneficial burning.
Scenic pics at http://Lhfotoware.blogspot.com
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sunflower Posted 5:45 am
26 Jan 2007
Our greatest hope is that the emperors see God before we all burn up with hell on Earth.
I felt pall and impatience after SOTU and was quiet depressed (and smart enough to keep my mouth shut the following morning). At best, DR was complaining about (and contributing to) irrelevant babble.
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sunflower Posted 5:51 am
26 Jan 2007
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caniscandida Posted 5:59 am
26 Jan 2007
I think most of us understand that the tree-planting off-set industry is complicated. Hopefully. Hopefully, most of us understand by now that where trees are planted matters, regarding reflectivity vs. absorption of solar radiation.
Also, as a Latin teacher, I think it would be nice if people curious about "albedo" should start reaching out curiously to the Latin teachers in their neighborhoods. E.g., there is a reason why I fly the flag of my Little White Dog as "Canis Candida," and not as "Canis Alba."
There was nothing particularly "true" about David Roberts' rave, except inasmuch as he felt "truly" insulted that his point of his view was not accepted universally as gospel "truth."
I really have no interest in that magical house whatsoever. I do indeed dislike the graceless way in which DR reacted to certain criticisms of it, regardless of their value.
And syntax-wise, it is not clear whom good old Tom Philpott is accusing of "pretty reactionary and specious terms."
DR himself? OK, he is the boss, he gets to write whatever the hell he wants to write, the rest of us do not, so let him defend himself: not that he has not already done so adequately, and more than adequately, ad nauseam.
Somebody other than DR? Gevalt! Whom?! Shame on you, Tom Philpott. NOBODY who has criticized DR on this matter is opposed to good general environmentalist values, and you know so.
The point is DR's style, not the content of everyone's discussion. Nicht wahr?
One of my best beloved prophets, Sunflower, writes:
<<
My greatest fear is that passion will flame out and we all become flat, quiet, accepting death as it is.
My passion is on fire.
>>
A dread of mine is that DR is doing his best to flame out passion, to get us to become flat, and to accept death. While looking very very cute and radical.
Everyone's passion should be on fire.
God knows, we do not, damn it, need to wait for David Roberts to give us the green light to proceed.
Chickens are our cousins!
So are other sensitive animals!
Enough is enough!
No more factory farms!
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sunflower Posted 6:38 am
26 Jan 2007
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GreenEngineer Posted 7:12 am
26 Jan 2007
No bet. And I liked the corn ethanol analogy.
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willa Posted 7:30 am
26 Jan 2007
I am a total failure at Latin, though. Greek, too. I thought it would make me feel smarter to read Plato in Greek, but all it did was make me stay up till 4AM studying every single night my freshman year...
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caniscandida Posted 8:09 am
26 Jan 2007
Chickens are our cousins!
So are other sensitive animals!
Enough is enough!
No more factory farms!
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bookerly Posted 8:30 pm
26 Jan 2007
While I am not going to argue that mono culture forestry is a good idea, there are other benefits to tree planting than fighting global warming. In some cases, it may help fight the steady march of deserts, and certainly it helps create a more pleasant urban environment.
I do agree that the idea that tree planting as a carbon offset doesn't always work, but there are other reasons to plant them. Aren't there?
(hopeful smile)
patrick
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SMLowry Posted 9:43 am
27 Jan 2007
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Gar Lipow Posted 9:52 am
27 Jan 2007
>I do agree that the idea that tree planting as a carbon offset doesn't always work, but there are other reasons to plant them. Aren't there?
Sure. Just don't plant them for those other reasons, and then sell carbon offsets from them. Let me see if I can be much more succinct than usual:
Tree good. Phony carbon offset for planting tree bad.
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Gar Lipow Posted 9:58 am
27 Jan 2007
To do that you either have to tear up the asphalt or add pots - a fair amount of energy expenditure. If the latter case you will have to add irrigations (since trees in pots can't tap groundwater) and significant pest management (since you can't use biodiversity as a defense).
>are adding shade to city sidewalks, are part of a restoration effort of a landscape scarred by wildfire? Would these tree plantings still be considered to produce a net warming effect?
Depends. However the key is you are not going to generate many carbon credits. Carbon credits from trees requiring planting lots of the things. And that probably means displacing existing plants. Look trees are great things. There are lots of reasons for planting them. But generating phony carbon offsets from them, and using those offsets as an excuse to continue burning fossil fuel is not one of those reasons.
I'm still not sure I'm buying the significance of the albedo issue. Granted, I'm not a forestry scientist, so should have no rights to question the conclusions of the paper... yet, it just doesn't make sense to me. By that logic, Maine, which has tons and tons of dark, leafy trees, should be warmer than Kansas, which is flat prairie land. No?
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GreenEngineer Posted 11:17 am
27 Jan 2007
Certainly I believe this result when comparing snowy plains to forest. Snow has a very low albedo (~0.1?). Forest is much higher (0.4-0.6 if I recall, though I may be off), which means a 4x - 6x increase in the amount of heat absorbed from solar radiation.
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Gar Lipow Posted 11:39 am
27 Jan 2007
>Certainly I believe this result when comparing snowy plains to forest. Snow has a very low albedo (~0.1?). Forest is much higher (0.4-0.6 if I recall, though I may be off), which means a 4x - 6x increase in the amount of heat absorbed from solar radiation.
Thanks GreenEngineer.
That last paragraph was quoted, and I meant to reply to it, but missed it in posting so thank you for doing so, and incidentally doing a better job than I would.
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Backcut Posted 11:44 am
27 Jan 2007
I'm NOT saying that we should ramp up the cutting of old growth, though. Endangered species habitat is more important than our own desire to have lots of trees. For example, since the early 90's, here in California, we've been barred from cutting even mid-sized trees, to "save" the non-listed California Spotted Owl. Now, those "owl circles" are so crowded that they're in danger of being completely lost.
Also, there's a problem with "NIMBYism". Preservationists first pushed for saving the old growth. Then they said they didn't want us to cut those mid-sized trees. Now they're demanding that we stop cutting even dead trees. In the meantime, we're seeing huge increases in tree cutting in places where there's much less in the way of environmental protections. Will the NIMBYists take credit for THAT?!?
Really, though, I truly love forest ecosystems. you're right that they are food for the soul, SMLowry.
Scenic pics at http://Lhfotoware.blogspot.com
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sunflower Posted 12:07 pm
27 Jan 2007
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sunflower Posted 12:32 pm
27 Jan 2007
Carbon creditsMy grandfather once said, "Don't let the truth interfere with a good story". Reducing fossil carbon by planting trees is like holding your breath for longer life. Planting trees will not work, but it was a good story.
If trees are burned to displace the burning of fossils, then carbon credits are well earned. Trees are a carbon neutral source of energy.
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