UK Pine Plantations May Be Net Carbon Sources, Not Sinks - Independent

[hatrack]

How much carbon dioxide does a forest soak up? It's an important question because planting forests is one of the actions that countries can take to offset some of their carbon-dioxide emissions, and achieve their target set by the Kyoto Protocol - the agreement drawn up by developed countries, in 1997, to limit their greenhouse-gas emissions. And coniferous plantations, with their trees laid out in neat rows, are valuable commercially for their timber, as well as being an environmental asset by helping to soak up some of the carbon dioxide belched out by power stations, traffic and industries. It is no wonder then that these plantations are springing up all over the developed world, as governments race to get their green credits established.

But, unfortunately, coniferous plantations may not be as "green" as they might appear. Recent research from Scotland suggests that commercial plantations are not soaking up as much carbon dioxide as was first thought, and that sometimes they may even be contributing to the global-warming problem. Dave Reay, and his colleagues from the School of Geosciences at the University of Edinburgh, have discovered that the practice of thinning trees in plantations turns the forests from absorbers of carbon dioxide into producers of it.

Just like a gardener needs to thin out their baby lettuce, carrot and cabbage plants, forestry managers need to thin out their young trees. Thinning stops the plants and trees from overcrowding and gives them the space to grow. The result is tall, strong and sturdy trees, which are valuable commercially. But unlike the gardener, who thins out seedlings using a finger and thumb, the forestry manager has to thin the forest using heavy machinery, which makes a much bigger mess. Roughly every fifth row of trees is chopped down; the branches are stripped from each tree and the trunks taken away to the sawmill. Huge piles of branches, called brash, are left behind, to rot into the ground.

And this is where the problem lies. Bacteria that decompose plant matter gobble up the brash and react with oxygen to produce carbon dioxide, water and energy. Much of the carbon that was once stored in the brash is released back into the atmosphere as carbon dioxide."

EDIT

http://news.independent.co.uk/uk/environment/story.jsp?story=597557

[bobweaver]

1. Then explain this to me...

If forests contribute to global warming, how can it be that so much of the original forest area of the world has been deforested - yet global warming still continues. If forests are truly the cause of global warming, then the massive deforestation that has taken place over the last 300 years, all over the world, should have prevented or slowed down global warming. I don't buy it.

[DavidDvorkin]

3. Mature, natural forests

That's what has been cut down all over the world. Such forests are not crowded and don't have as much decaying matter at one time as described in the article.

[bobweaver]

4. Thus it would follow that...

...natural, uncrowded forests do not contribute to global warming. Crowded, man-made forests do, and forests that man allows to become overcrowded due to fire supression do, but forests in their truly natural state don't. Thus man is the cause of global warming, not nature.... ???

[DavidDvorkin]

5. Yeppers

[Viking12]

6. Biodiversity is the key to sinks

Studies conducted at the University of Minnesota have demonstrated that the more diverse a forest or grassland, the better they sequester carbon. The problem with the pine plantations is that they are monocultures.

[hatrack]

7. In addition, as monocultures, they're goosed with fertilizer

This means that soil nutrients cycle through faster, and aren't necessarily replaced, leading to long-term nutrient depletion and less carbon capacity. The Swiss and Germans are on their third generation of monoculture forestry in many areas, and are really having problems - which aren't helped by acid rain & climate change.

In addition, Duke has been running some large-scale studies on enhanced CO2's effects on pine trees. What they've found after about 10 years is that trees in a high-CO2 atmosphere have an initial growth spurt, and then slow below average.

The big hope of some was that more CO2 would mean faster tree & plant growth, thus absorbing the excess CO2. It does work, but only at first. Soil nutrients just run out faster, throttling back carbon storage. Oh well . . .

[Inland]

2. Showing that you gotta think things all the way through.

[NNadir]

8. It would be a mistake to misread this article.

The "Brash" like all cellulosic matter is 40% carbon. When this material is oxidized, of course, it is reinjected into the atmosphere, but I emphasize it is REinjected, not injected, as in the case of a fossil fuel. In fact 100% of the carbon in "brash" has been fixed from the atmosphere. During the formation of the brash, carbon is being sequestered, albeit temporarily.

All forests ultimately come into equilibrium with respect to carbon, unless of course, the organic matter in them is carbonized, i.e. unless the forests end up fossilized as peat or coal deposits. This is as much true of old growth forests as it is in agricultural "forests" which might better be termed "tree farms." The ability of tree farms and or natural forests to sequester carbon is a function of total area devoted to them. It may be true that real forests achieve these results with higher efficiency, tons of carbon per hectare, but this does not imply that tree farms are necessarily an anathema. They are only so if they displace natural forests. This is an important distinction.

The net carbon impact of these operations is highly dependent on the nature of the fuel used in the mechanical processes, the nature of the processes themselves, and, as it is with all forms of energy, the distance that must be traversed by the processed materials. If it happens that the fuel machinery for managing the tree farm must come from great distances, it is possible that the tree farm will be a net injector of carbon, but this need not be the case. Wood that is used to make paper or construct houses, wood that is processed into biopolymers like cellophane, is, in fact sequestered. Before anyone tells me that wood rots, I would like to note that I have personally seen wood carvings in the Louvre that are many, many thousands of years old. I would expect that some wood now being processed, especially that which is coated with urethanes, will remain with us for many centuries at least.

I note in passing that it is theoretically possible to power machinery from the energy obtained from either the gasification or processing wood product waste into "bark oils" or methanol. For instance, in Energy & Fuels 2004, 18, 704-712, in a paper entitled "Colloidal Properties of Bio-oils Obtained by Vacuum Pyrolysis of Softwood Bark. Characterization of Water-Soluble and Water-Insoluble Fractions," to give just one example, the properties of such oils are discussed. While it may be true that such oils have low energy density and poor long term stability, they are perfectly viable fuels for in situ use. These oils, in fact, are made from "brash."

Most environmentalists, myself included, have a John Muir type sensibility. We love the natural state, free rivers and ecologically diverse systems like old growth forests. These things are of course to be treasured and we must fight, like John Muir did, to preserve as many of them as possible. Sometimes we will lose, just as Muir lost the Hetch Hetchy to the detriment of future generations that now include us. Still we need to keep some perspective. At least the Hetch Hetchy was not destroyed for a strip mine, but for a lake that generates some energy. Similarly, a tree farm does not represent the worst possible case of land use. It is merely just more agriculture. Somehow I prefer a tree farm to a strip mall or a housing development, just as I prefer a corn field to a parking lot.

[rfkrfk]

9. Carbon 'Sinks', are a fraud

Carbon sinks, are a scam perpetrated by the
Kyoto-faithless countries, with the intention of
avoiding reponsibilities to the treaty.
Don't believe a word of this.
Follow the money.