Planting Trees Doesn't Necessarily Mitigate Global Warming

We've all been thought, "Plant a Tree, Save the Planet" or something like that. But a new research seems to indicate that it may not necessarily help, and in some cases, it would bring about the opposite effect.



So I suppose it's up to us people living near the equator to save the Planet. Well good luck with that. We're all doomed.

I find it amusing that climate 'scientists' have only now discovered what foresters have known for three hundred years.


The amount of carbon absorbed by forests is only a fraction of the amount absorbed by the oceans, but forests can help if managed properly.

Carbon sequestration in trees is a function of the amount of woody volume added every year. But the amount of wood volume added each year is not a linear constant. If charted (time on the X axis; volume on the Y axis) the growth curve is S shaped. Young trees absorb relatively little carbon as growth mostly takes place in the foliage and root system. As the tree matures and begins its rapid growth stage the amount of wood volume added each year increases sharply. This is the stage where most carbon is absorbed. As the tree enters senescence the rate of growth slows and little net wood volume is added each year. This is why old growth forests do not remove any additional carbon from the atmosphere -- they store a huge amount of carbon but do not remove any additional. Old Growth forests are carbon nuetral. The amount of growth each year is negated by the carbon released through death and decay. In extreme senescence the forest may be a net carbon emitter.

To maximize the amount of carbon removed by forests the forest must be managed properly and the largest possible amount of the forest must be kept in the rapid growth stage. Harvest the trees as soon as the rate of growth slows and replant with young trees. Store the removed wood volume off-site -- the walls of buildings are an excellent location.

There are many reasons the preserve old growth forests -- biodiversity, aesthetic, recreational, and spiritual values, to name a few. But carbon buffering the atmosphere is not a reason. In fact, as I mentioned earlier, old growth preservation is actually a global warming enhancer.

Sometimes environmental and natural resource decisionmaking involves tradeoffs, accepting a small negative to have a greater good. Too many in the environmental industry are unable to grasp that concept.

What about old growth forests/jungle near the tropics or equator? What's your opinion on them? How should they be managed based on your knowledge of forestry and the article above? You seem to know the subject intimately, are you a forestry worker?

Edit to add: BBC caught up with this a day later (15th Dec 2006).



Just adding this to highlight the issue. I live in the tropics.

[edit on 16-12-2006 by Beachcoma]

ummm... no.

I don't buy it

Plant a tree, watch a bird land on it and sit there for a while chirping. Consider the fact that before you did it... that point in space was whatever temperature the ambient air was. Now it is cooler. Moist, inside of tree, cooler.

What is the urban heat island effect if planting trees only makes things warmer?

I've planted hundreds of trees and will keep on.

Sri Oracle

I'm not buyint it either. Trees provide shade.

Lawrence Livermore Lab is a nuclcear physics plant, there's not one single biologist, climatologist or any other life sciences expert at the facility.

It's a study done by one man and it completely ignores the fact that carbon dioxide is by far the biggest contributor to greenhouse gases.

Dave 54, I realize that you are positing a theory, which I respect. However, it is highly disputed among scientists as to whether or not algae contributes more oxygen than trees/plants.

What most people don't realize is that an incredible amount of scraping of the sea floor is going on and it's rapidly destroying algae which does produce oxygen. It's a big reason why life in the ocean is dying rapidly. And it is also a huge contributor to global warming.

Not theory. The gas exchange in a forest canopy was modeled and theorized for years. Actual data was hard to obtain, since forests are open to the atmosphere and gas sampling is difficult. In the mid 1990's, The Forest Service Southern Research Station decided to find out for certain. They rented several large 'big top' circus tents and erected them over both native mixed age/mixed species forests, and planted even-aged forests. Sealed the tents, installed lighting and sensors, and measured the actual gas exchanges. The previously held conventional wisdom was determined to be correct. Mid seral forests absorb the most carbon and old growth does not. In light of the findings, the authors of a widely circulated 1992 article in Nature magazine (their modeling asserted old growth is a net carbon sink, but their modeling methodology was widely criticized) publicly repudiated their earlier paper in 2001.


How forests affect microclimate is highly variable. A canopy shades the ground, but raises the temperature of the boundary layer immediately above the canopy. Relative humidity is slightly higher below due to the lower temperature, and seasonal soil moisture stays longer. Air exchange is restricted below the canopy, as wind flow is reduced.

Hydrologically, it has long been known that in forested watersheds maximum water yield is obtained with the forest at 80% normal stocking. Tree density above that level actually decreases water yield, as the canopy intercepts precipitation. Below that 80% level, increasing solar radiation on the ground reduces soil moisture. This is for temperate forests. Tropical forests may have a different response.

How all these factors interplay is very complex. And since forests provide many other attributes and values than atmosphere mitigation the various costs and benefits of different forest management philosophies cannot be decided by science alone. All factors, social, economic, and political as well as scientific, must be considered. As scientists are trained to ignore the other values (and in most cases consider only their narrow field of expertise), they are singularly unqualified to make the final decisions on forest management or global warming.

Huh? Scientists aren't qualified to make final decisions on global warming? Who else, on your planet, agrees with that? Orwellian logic is not logic.

Scientists are not trained to ignore everything but their own narrow specialty. There are some out there who do think like that, but I can assure you that's not what they're taught. My husband, a biologist, is one of the most knowledgeable people I know, and he's knowledgeable in all sorts of areas. When it comes to global warming, there are all kinds of different scientific specialties and they all share their findings to better fill in the holes and to subtantiate their findings.

If scientists shouldn't be the ones to determine such things, who should?
And, how do you account for the Amazon jungle providing 1/6 of the world's oxygen? (Hint: it used to provide 1/6 up until the early '70.s The Amazon jungle is shrinking by astoninshing speed, and as it does, less oxygen is produced).