On tree planting

On tree planting

22 Jan 2007

Got questions about the environment? Ask Umbra.

Dear Umbra,

My wife recently heard a program on NPR where an expert on global warming said that planting trees in the Northern Hemisphere plays a negligible role in fighting global warming, while playing a significant role in the Southern Hemisphere. Do you have any light to shed on this?

Randy Cunningham, Confused Tree-Hugger
Cleveland, Ohio

Ask Umbra continues below

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Dearest Randy,

Tree hugging has no proven deleterious effect on climate change. What you should not do, however, is try to compensate for your carbon production by planting huggable forests, according to the results of a study by the Lawrence Livermore National Laboratory and Carnegie Institution Department of Global Ecology.

Now you seed it, now you don't.

Photo: iStockphoto

The study was in the news in mid-December, and I too heard it reported on NPR. The study authors put together a large-scale computer model of forests' role in global warming, and your wife clearly remembered the outcome. Planting gobs of new forests in temperate zones, it seems, will have a negligible or even negative effect on global warming in the long term. Tropical forests, on the other hand, will have a positive effect, the study said.

How is it true that trees could be bad for something?

Doubtless you are familiar with the concept that trees uptake carbon and have helped ameliorate our recent carbon loading of the atmosphere. Trees also evaporate water and contribute to cloudiness, keeping things a bit cooler. What swung these positive effects to the neutral or negative in the large-scale climate model was a third property of forests: albedo.

Who remembers this term from their climate reading? It means reflectivity, basically. It comes from the Latin word for white, and is similar to albino -- but not libido. Forests, all dark with leaves and stuff, have a low albedo. Shiny ice sheets have a high albedo. Remember one problem with the (predicted) end of summer ice in the Arctic is the permanent ice sheet's current role in reflecting sunlight and heat away from Earth. As the ice disappears, warming may increase rapidly when the high-albedo surface provided by miles and miles of whiteness is replaced by darker, lower-albedo ocean water.

Since forests don't tend to reflect heat, they hold a lot of warmth. When the study authors integrated albedo into their computer model, they found that replacing grasslands and other non-forested areas with forests in temperate zones (e.g., North America, Europe) would eventually lead to net warming of the Earth. In tropical areas (e.g., Brazil), forests exhale more water; scientists say this contribution to cloudiness will help cancel out the warming effect.

Obviously this conclusion could be big trouble for companies and countries intending to rely on tree planting in temperate zones as a carbon offset tactic. It could also be twisted into fodder for those who practice industrial deforestation. For us individuals it is an interesting new piece of information -- trees cannot save us from ourselves! -- which I suppose can only further inspire our efforts to reduce our fossil-fuel emissions. I know, I know, I make all topics lead to that same conclusion. What can I say?

Borealy,
Umbra

Yours is to wonder why, hers is to answer (or try). Please send Umbra any nagging question pertaining to the environment -- but first check out her FAQs!

The claims made in this column may not reflect the views of this magazine. Neither the magazine nor the author guarantees that any advice contained in this column is wise or safe. Please use this column at your own risk.

Umbra Fisk is Grist Research Associate II, Hardcover and Periodicals Unit, floors 2B-4B.

Comments: (18 comments)

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planting trees

Dear Umbra, Just wanted to share a related reference that gave me a perspective on this topic. The article is "Individualization: Plant a Tree, Buy a Bike, Safe the World?" in the book Confronting Consumption by Thomas Princen, Michael Maiates and Ken Conca. Helps clarify the consumer vs the citizen actions that really make a difference on a large scale.

Ellie Goldberg, M.Ed. www.healthy-kids.info

by HealthyKids at 10:14 AM on 22 Jan 2007

a complicated topic

I've tried this on numerous occasions, only to become frustrated by the matter. I searched the literature for a short time -- though longer than I should have -- and found the issue of exactly which biome sequesters more carbon still quite difficult to identify. It goes without saying, for most Grist readers, that it is very complicated and depends on climate, soil type, water, et cetera. Factor in albedo and transpiration and I'd rather have a professional just tell me what to do.

Here is a tiny bit of information from a paper published in Ecological Applications, Vol 10, No 2. I had to add up the values the authors presented in thrir Table 3 to get total SOC (soil organic carbon).

A list of biomes and SOC in kilograms/square meter...

Boreal Forest 25
Crops 35
Desert 23
Sclerophyllous Shrubs (whatever they are!) 29
Temperate Deciduous Forest 46
Temperate Evergreen Forest 41
Temperate Grassland 38
Tundra 36

Crops, Temperate Forest, Grassland... not much diffferent.

The tropical forests and tropical grasslands have much higher values.

Another paper described something referred to as SIC (soil inorganic carbon). The authors mentioned that is plays an important role in LONG-TERM carbon storage, but the process is largely not understood. I don't have the reference in front of me, but I can find it again if someone is interested. Surprisingly, in this case, shrubland and grassland lead the pack, forests are dead last. This suggest grassland might be useful as a long-term carbon sink.

Does anyone know more about SIC? Sounds rather important.

I can conclude two things at this time:

(1) PLANT SOMETHING! But make sure it is appropriate for the climate and soil in the area. No point in planting deciduous or evergreen trees if they burn to ground on a regular basis (unless their adpated to that sort of environment).

(2) Our government should fund further research on natural carbon cycles so we don't further mess things up by promoting the planting of the wrong flora in the wrong places. I cannot imagine how this task can be left to private enterprise.

Just food for thought.

by wiscidea at 12:33 PM on 22 Jan 2007

The problem with planting trees

Another issue with planting trees is that so few of them actually survive for long. For most species you must plant dozens, sometimes hundreds, to make up for the loss of one tree, because most die within the first few years. Planting a single tree is unlikely to do much good anyway.

by moonwatcher at 1:00 PM on 22 Jan 2007

Pick your spots

Remember, though, that in many areas of the southwestern US, forests are ALREADY way overstocked and experiencing enhanced drought, above and beyond that of the rest of the west. In some forests, there's up to 100 times more trees than were there before the white man came. Now, before you jump all over me (again), I freely admit that this comes from mismanagement of our forests throughout the last decade. Fire suppression, heavy-handed logging and preservationism has impacted our forests so much that were seeing the results of that mismanagement in record fire years, unnatural bark beetle infestations and over-harvesting of private timberlands (in response to locked up Federal forests).

Often times, after fires, I have seen "carpets" of natural regeneration with THOUSANDS of seedlings per acre. I guess this is part of nature's plan but, she tends to work on timescales that boggle our minds. In some areas, it may take 500 years to return the land to towering fat pines and mega-biodiversity.

THAT'S what I want to see but, I think us humans can speed up the process of restoration. That being said, carefully pick your spots but, make sure ya plant em green side up....lol.

Scenic pics at http://Lhfotoware.blogspot.com

by Backcut at 1:32 PM on 22 Jan 2007

impulsive vs. informed environmentalism

I perceive an emerging conflict between, for lack of a better term, impulsive and informed environmentalism.

Tree planting is one example. I'd swear I've been indoctrinated for almost my entire life -- via the education system and mass media -- that planting trees is always a good idea. Folks dreamed of covering the landscape with trees. Fire was an enemy. Reforest the barren land. Tree planting is almost synonymous with being a steward of the Earth. Cutting down a tree is considered evil.

Then I moved to southwest Wisconsin and learned about the pre-settlement landscape... savanna. And I learned about endangered grassland birds, about ancient trout streams overgrown by tangles of vegetation, about how the settlers suppressed natural fires and changed the ecology.

For several years, I've worked toward liberating my tiny bit of grassland from invasive trees. The first reaction of one of my friends was something like... "Oh my God! How can you cut down those boxelder trees and set fire to the grass! What about the poor animals?" Well... I had to explain it was for the greater good. There are insects, birds, and mammals that prefer grassland over shaded dirt.

I've also volunteered to help the Nature Conservancy a few times and learned that their activity is not always welcomed by the community. Many people don't undertand that removing the red cedars from a hillside and burning the area is good for wildlfe, a net gain for biodiverstiy. They think the trees are "normal" and that bare land -- otherwise known as prairie -- is bad.

This is a public relations problem that must be addressed.

by wiscidea at 2:50 PM on 22 Jan 2007

Again, balance is best

Well, since we had almost 10 million acres burn last year, there should be plenty of spots to plant lots of trees. Wiscidea is being truly progressive in restoring land back to a balanced and natural state. Some ornamentals are alright to plant but, one of my pet peeves is the planting of water-intensive species in arid cities. Yep, Sacramento has some streets lined with redwoods and alders, with green grass underneath. Talk about "water hogs"! I'd think that a native oak with decorative rocks underneath is more ecologically-sound.

If you live in the West and want to get involved, I'm sure there's plenty of volunteer programs that involve planting trees in burned areas. It's also amazing to go back years later and see how well your baby trees are doing.

Scenic pics at http://Lhfotoware.blogspot.com

by Backcut at 3:46 PM on 22 Jan 2007

street trees

One cautionary note before we write off tree planting entirely - the article and the comments have raised some valid issues, but run the risk of leaving the reader with the sense that tree planting is of marginal value.

Most of our cities have become "heat islands" as a result of hardscaping and the removal of open space (see, www.epa.gov/heatislands/about/index.html). Typically, a city's downtown can be 10 degrees F hotter than the outskirts. Hotter cities mean more electricy use which means more CO2 in the atmosphere. Street trees, parks, and other open spaces can have an enornous cooling effect. So while I think it's true that we should be cautious in trying to create or extend natural forested areas, we should be doing far more to create and preserve the urban forest.

Tom Kelly

by kyotousa at 5:03 PM on 22 Jan 2007

well...

While I have not read the study, it would seem that this would be predominantly true for boreal forests and conifer plantation more than other types of trees. Deciduous trees obviously have higher albedo, while evergreens do not. If factoring in methane evolution with boreal conifer removal with the warming of the soil during the summer, I would believe that this thesis would drop out as well. I guess the main thing that can be said about this is that there should be less conifers planted in temperate zones, but this is a difficult proposition for some since conifers are much easier to establish then deciduous trees (but worth less also, so an interesting caveat).

I find it somewhat of a dubious statement that boreal forests contain the least organic carbon in the soil. They are net sinks of carbon, due to peat production and Podzols, which is not the same as SOC. Basically what I think happened with wiscidea's citation was the various authors were measuring soil organic carbon in the upper profile or the pedon. Depending on the climate, and type of soil much of that carbon will be continuously leached from the upper horizons into lower ones, creating a sink (this might change with warming).

by atreyger at 5:24 PM on 22 Jan 2007

Oops!

"Now, before you jump all over me (again), I freely admit that this comes from mismanagement of our forests throughout the last decade."

That should really be "the last century", although both Bush and Clinton both have done an inadequate job as forest stewards.

Scenic pics at http://Lhfotoware.blogspot.com

by Backcut at 5:32 PM on 22 Jan 2007

urban trees, boreal forests, and podzols

Please don't interpret my comments as a rant against tree planting! I'm only concerned that people will incorrectly perceive trees as ALWAYS the appropriate vegetation for an area.

In urban areas where water is available trees are important for cooling, shading streets, creating a more pleasant environment, providing resources for wildlife, et cetera. Properly located, they can reduce energy demand for air conditioning and heating. The value of a tiny meadow or patch of short-grass prairie -- genetically isolated and too small to serves as someone's nesting territory -- is probably minimal in an urban area.

Regarding the boreal forests, that's the best info I've managed to find so far. I'll keep searching for clearer data. There is also the question of above ground organic matter. The paper I cited did look at SOC at different depths; I added up the values to get total kg per square meter.

Regarding the podzol, perhaps that is where SIC (soil inorganic carbon) enters the picture. I'll track down that paper again to see what the authors say about boreal forests.

This is obviously not my area of expertise, but it is something I'm very interested in learning about. I presented the information to stimulate some discussion of the value of different ecosystems for sequestering carbon and hoping that someone might bring better information to our attention.

A better question would be...

What is the net carbon gain observed for each biome? For the moment, I'm assuming a biome's SOC reflects its ability to sequester carbon. Perhaps it just indicates the plants grow better in a certain climate or on certain soil.

If anyone can direct me to CLEAR and SPECIFIC information about net carbon gain for different plant communities in different climates, please send the link or reference to wiscidea@yahoo.com. Or post it here. Thanks!

by wiscidea at 6:49 AM on 23 Jan 2007

"sclerophyllous"

That ought to mean, "having hard leaves." E.g. yucca?

Would the world be a much poorer place, if we did not have tequila? And mezcal, con gusano? Yo pienso que Si.

All the same, this conversation is one of the most brilliant ever hosted by Gristmill. And I say that, with no reference whatsoever to my mad crush on Umbra Fisk.

Plus, I have long enjoyed the contributions of WiscIdea, and I am glad that he/she has got over his/her depression.

As for Backcut's nervousness regarding being "jumped all over," one would first have to have relevant photos of the jumpees. Nicht wahr? My guess, purely founded on prejudices of one kind or another, is that Backcut is quite safe.

Chickens deserve our true friendship! So do fish! So do other sentient beings! Let us learn to be kind.

by caniscandida at 7:23 AM on 23 Jan 2007

Deforestation = 25% of all carbon emissions

FROM: http://www.ecobridge.org/content/g_cse.htm
After carbon emissions caused by humans, DEFORESTATION is the second principle cause of atmospheric carbon dioxide. Deforestation is responsible for 25% of all carbon emissions entering the atmosphere, by the burning and cutting of about 34 million acres of trees each year. We are losing millions of acres of rainforests each year, the equivalent in area to the size of Italy. [Rainforest Action Network. Press Release, October 16, 1996]. The destroying of tropical forests alone is throwing hundreds of millions of tons of carbon dioxide into the atmosphere each year. We are also losing temperate forests. The temperate forests of the world account for an absorption rate of 2 billion tons of carbon annually. [Keeling, Ralph, Stephen Piper, Martin Heimann. "Global and hemispheric carbon dioxide sinks deduced from changes in atmospheric oxygen concentration" Nature,Vol.381 May 16, 1996.]. In the temperate forests of Siberia alone, the earth is losing 10 million acres per year.

Richard Rowe Wofford Heights, CA in the Idyllic Kern River Valley

by RichardinKRV at 7:45 AM on 23 Jan 2007

Albedo is being considered incorrectly

Areas covered in ice have a high albedo, however, those areas are too cold to grow trees (otherwise, they wouldn't be covered in ice). They can't be used for planting trees anyways, so albedo there is irrelevant to the question, or may even be a reason to plant trees in addition to carbon storage.

Cities have high concentrations of asphalt, which has a lower albedo than trees. Hence, for every large shade tree planted in a city, once it gets big enough to start shading houses or roads, it is actually raising albedo. Trees, in city yards, already store much more carbon than grass (and grass mowing contributes to carbon emissions). The problem becomes not just that we need more trees, but that we need them to replace grassy areas in people yards, not prairie (which stores at least five times as much carbon as grass typically grown in a yard, more if it contains some shrubs or small trees).

In short, plant a tree. Plant a long-lived tree, adapted to your local climate, which can spread out and shade a significant area, and is unlikely to be killed by disease or pests. And plant it in your own yard, where you can be sure it won't be cut down.

by banana republican at 9:28 AM on 23 Jan 2007

quick reference

Total net primary production (NPP) of the major biome types (carbon fixation - respiration) in g m^-2 yr^-1:

tropical forests: 2500
temperate forests: 1550
boreal forests: 380
mediterranean shrublands: 1000
trop. savannahs and grasslands: 1080
temp. grasslands: 750
deserts: 250
tundra: 180
crops: 610

Saugier et al. 2001.

by atreyger at 12:00 PM on 23 Jan 2007

p.s.

Saugier, B., J. Roy, and H.A. Mooney, 2001. Estimation of global terrestrial productivity: toward a single number? pp. 543-557 in Terrestrial Global Productivity. Academic Press, San Diego, CA.

percentages of global carbon stored in soils by biome:

13% trop. forest
8% temp. forest
9% savannah
13% boreal forest
11% grasslands
15% wetlands
14% tundra
12% crops
6% deserts

from Perry, D.A., 1994. Forest Ecosystems, p. 40. The Johns Hopkins University Press, Baltimore and London.

by atreyger at 12:44 PM on 23 Jan 2007

Thank You

astreyger

Thank you very much for the reference. I looked at the information available online and found the book -- Terrestrial Global Productivity -- very interesting and very thorough! I noticed he also covers decomposition of organic material, which was going to be my follow-up question... what is the net carbon gain year after year, not just fixation minus respiration? He also discusses biodiversity. I imagine he sorts out the above-ground vs. below-ground and SOC vs. SIC issues as well. I've requested the 500+ page tome from the library and look forward to reading it.

Grist

Thank you very much for providing this valuable service, which enables everyone to find the information they need to understand how we affect the world and how we might repair the damage.

by wiscidea at 1:33 PM on 23 Jan 2007

wiscidea

You are most certainly welcome, I am glad that I could help out. If it helps you a little bit more, the net carbon sequestration by an ecosystem is called Net Ecosystem Productivity (NEP), I think that this criterion is a more difficult one to calculate, but there are plenty of scientists who are trying and succeeding, or the global climate models wouldn't be worth a damn.

by atreyger at 11:24 AM on 24 Jan 2007

I gotta agree here...

Trees are at the far end of the plant evolutionary scale -- as such they consume a lot of resources to make their big trunks.

Greenpeace and Earth First would help the planet more if they went around planting ferns.

by jabailo at 10:52 AM on 26 Jan 2007

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The Problem of the Root